NATIONAL RADIO COMPANY NCX-5 Transceiver User Manual

NCX-5 Transceiver

Product Information

The NCX-5 Transceiver is a high-quality communications device
manufactured by National, one of the oldest and most highly
respected manufacturers of communications equipment. With a history
of nearly half a century, National has a reputation for producing
superb communications devices. The company has a team of highly
skilled test and assembly personnel, many of whom have been with
the company for over 25 years.

National manufactures most of the components used in their
equipment, giving them control over the quality of each part. They
also supply electronic components to other important electronic
manufacturers and government agencies.

Product Usage Instructions

Before using your new NCX-5 Transceiver, it is strongly
recommended that you carefully study the instruction manual
provided. Understanding the controls and operating features will
ensure maximum performance.

If your National equipment requires servicing, you have several
options:

1. Return it to the dealer from whom you purchased it.
2. Bring it to one of National’s authorized service agencies.
3. Write to the Service Manager at National Radio Company, Inc.,
   providing details of the difficulty, including the type of unit and
   serial number. If necessary, National will provide written
   authorization to ship the unit back to the factory.

If your unit is deemed defective by National within 90 days from
the date of purchase, repair or replacement will be provided at no
cost to you. After 90 days but before 365 days have elapsed,
National will provide a replacement for any defective part
(excluding vacuum tubes or transistors). Labor costs for
installation, if required, will be billed separately.

It is important to inspect your new equipment for any damage
immediately upon unpacking. In cases of in-transit damage, a claim
must be filed against the carrier.

Your unit will receive prompt and careful attention from
National’s service team to ensure any issues are resolved
efficiently.

37 WASHINGTON STREET · MELROSE, MASSACHUSETTS
NCX-5 TRANSCEIVER

–

You now own a product manufactured by one of the world’s which has been subjected to misuse, neglect, accident,

oldest and most highly respected manufacturers of qual.ity improper installations, or use in violation of instructions

communications equipment. National has manufactured furnished by us. Nor does it extend to units which have

superb communications devices for nearly half a century. been repaired or altered outside of our factory or its

Our experience is unequaled. More than 75 per cent of our authorized agencies, nor to units where the serial number

highly skilled test and assembly people have been with us has been removed or defaced.

for more than 25 years – an astonishing record in the Should your new National equipment require servicing

relatively young electronics industry. Our people know please do one of the following, whichever is most con-

their business … take pride in their fine workmanship –

venient:

workmanship so outstanding that many National receivers 1. Return it to the dealer from whom you purchased it.

purchased over 30 years ago are still in daily use.

2. Bring it to one of our authorized service agencies.

We manufacture most of the components used in our equipment … and, in fact, National has been a prime supplier
of electronic components to other important electronic
manufacturers and government agencies for many years. As a result, we enjoy unusual control of component part quality.

3. Write to the Service Manager, National Radio Company, Inc., 37 Washington Street, Melrose, Mass. and describe the difficulty. State type of unit and serial number. Describe as completely as possible the apparent defect. If we feel that the unit should be returned to the factory we will give you written authorization to ship the

We strongly recommend that you carefully study the instruction manual before attempting to use your new equipment. We C~re sure .you will find that maximum perfor-

unit to us. Notify us that you are returning the unit and ship prepaid and fully insured in the original specially designed shipping carton.

mance will be achieved with complete understanding of its controls and operating features.

Your unit will receive prompt and careful attention. If, in our judgment the unit is indeed defective, repair or re-

Your new National equipment has undergone an intense placement will be made at no cost to you if the unit is

series of rigio quality control tests. However, as with any returned within 90 days after date of original purchase.

complex electronic equipment, it is possible that a defect Should the unit be returned to us after 90 days from date

may appear as a result of rough handling during shipment or through circumstances beyond our immediate control.
For this reason, we suggest that you inspect your new equipment for such damage as soon as it is unpacked. In all cases of in-transit damage a claim must be filed against the carrier.

of purchase but before 365 days have elapsed, again, if in our judgment the unit is indeed defective, National Radio Company will provide a replacement of any such defective part (except vacuum tubes or transistors). If you wish us to install the part, you will be billed only for labor costs involved. At the end of one year, after expiration of

The component parts of this equipment (exclusive of va- guarantee, service will be billed to you at cost of parts

cuum tubes and transistors) are guaranteed to be free from and labor only.

defective material and workmanship, and repair or replace-

This extended guarantee super-

ment will be made on any part

sedes all previous warranties

found to be defective upon

of National Radio Company,

examination, provided that the

Inc. and is in lieu of all other

unit is delivered to your dealer,

warranties expressed or im-

authorized service agency or

plied. Damages arising out of

to the company, pursuant to

a breach of this guarantee are

the instructions below, within

limited to repair or replace-

one year from the date of sale

ment of the defective part as

to original purchaser. On units

stated above. We naturally re-

returned during the initial 90 day period, National Radio

NATIONAL

serve the right to change or improve our products without

Company, Inc. will absorb the labor cost of installation; for

ONE

imposing any obli.gation upon ourselves to so modify pro-

the remainder of the guarantee period the customer w~l be

YEAR

ducts previously manufactured. Your new National Radio Com-

charged for such cost. The enclosed guarantee card must

GUARANTEE

pany equipment is the finest of its type. It was sk ·

be returned to National Radio

designed, carefully

Company, Inc., within ten days

tured and thorou

from date of purchase in order

We are confident

to validate the guarantee.

choice of our r

I

Naturally, this guarantee does

result in many ears of plea-

not extend to any product

sure

. INDEX
Page
SECTION 1 GENERAL DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
SECTION 2 INSTALLATION …………………. …….. . …………. . …. . .. .. 3
2.1 Power Supplies 2.2 Mobile Mounting 2.3 Microphone Connections 2.4 Mobile Speaker Installation 2.5 Auxiliary Relay Control Terminals
SECTION 3 OPERATION. … . . ………….. … … …….. . . . . ……………….. 5
3.1 Tuning Procedures 3.2 Detailed Use of the Individual Controls
SECTION 4 THEORY OF OPERATION …… …. ….. … . …. . .. . . . . … . …. ….. 11
4.1 General 4.2 The Transmitter 4.3 The Receiver 4.4 The VOX Circuits 4.5 The Function Switches 4.6 Relay Functions
SECTION 5 ALIGNMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1 Equipment Required 5.2 Initial Control Settings 5.3 IF Alignment Procedure 5.4 Balanced Modulator Adjustment 5.5 Carrier Oscillator Setting 5.6 Transmitter Bandpass Tuning 5.7 Receiver Bandpass Tuning 5.8 VFO Frequency Alignment 5.9 VFO Linearity Adjustment 5.10 VFO Sideband Switching Adjustment 5.11 Temperature Compensating Adjustment 5.12 Transmit Mixer and Driver Alignment 5.13 Final Amplifier Preliminary Adjustment (10 Meter) 5.14 Neutralizing Capacitor 5.15 Final Amplifier Preliminary Adjustment (80-15 Meter) 5.16 Final Amplifier Tuning Checks 5.1 7 Local Oscillator Crystal Adjustment 5.18 Parasitic Check 5.19 Carrier Suppression, Sideband Suppression, Modulation,
and ALC Checks 5.20 Transmit-Receive Frequency Check 5.21 LSB-USB Switching Check 5.22 Switching Tests 5.23 Transceive Vernier 5.24 Anti-VOX Check 5.25 VFO Jack
SECTION 6 PARTS LIST. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
SECTION 7 VOLTAGE AND RESISTANCE MEASUREMENTS ………………… 26
1

SECTION 1
GENERAL DESCRIPTION

The NCX-5 is a five band high-performance transceiver for the 80, 40, 20, 15, and 10 meter amateur bands, intended for use in fixed home installations, as well as for portable and mobile application. The NCX-5 provides choice of SSB, CW, or AM operation with unusually accurate dial calibration and high frequency stability, together with operating features in all three modes normally available only with separate receiver-transmitter combinations.
A NATIONAL 8-pole crystal lattice filter with a 6 to 60 db. shape factor of 1.7:1 and a bandwidth of 2.8 Kc @ 6 db. provides sideband suppression and receiver selectivity previously found only in commercial communications equipment.
DIGITAL READOUT from a counter type display provides easy adjustment and resettability.
The SOLID STATE VFO eliminates the drastic initial warm-up drift so characteristic of tube type VFO’s. The stability of this VFO, together with crystal controlled high frequency oscillators, results in a remarkably stable double conversion receiver and transmitter combination.
A TRANSCEIVE VERNIER control in the NCX-5 allows independent adjustment of the receiver frequency from that of the ·transmitter section over a range of -+- 5 Kc from the displayed (transmitter) frequency.
SIDEBAND SELECTION is possible at the flick of a switch; (USB-LSB) without retuning the VFO. The operator may instantly select the opposite side-

band to reduce QRM or to make accurate SSB suppression checks with the calibrated S-meter.
ALC (automatic le·el control) is incorporated in the NCX-5. Effecti·e talk power is increased and microphone gain and speech loudness are made noncritical by this system. The 10 db. range of the ALC circuit in the NCX-5 prevents “flat topping” and splatter.
An ALC INPUT JACK is provided on the NCX-5 for use with the NCL-2000 2 Kw linear amplifier for control of the NCX-5 by the ALC voltage from the NCL-2000.
Choice of VOX-PTT-MANUAL operation is performed from the front panel when operating AM or SSB.
BREAK-1:f GRID BLOCK KEYING for CW operation accomplishes automatic transmit- receive switching at the tap of a key.
Two detectors are incorporated in the NCX-5: a product detector for SSB, CW, or “exalted carrier AM,” and an excellent diode detector for AM operation.
A VFO INPUT JACK on the rear apron connects to the VX-501 optional VFO console. The VX-501 , when used with the NCX-5, pro·ides completely independent control of transmit and receive frequencies, as well as transceive control by either the VX-50 1 or the NCX-5. Besides its ·Fo function, the VX-501 provides for crystal control oi !he :CX-5 transmit, receive or transceive frequencie;;.

2

SECTION 2
INSTALLATION

2. 1 POWER SUPPLIES:
The NCX-5 transceiver may be used with either the matching NCX-A 115/230 volt A.C. or the NCX-D 12 volt D.C. power supplies. We strongly recommend use of the National Power Supplies designed for the NCX-5 because of their extremely “stiff” voltage regulation and superior filtering.
NCX-A power supplies with serial numbers beginning with 73 or higher are designed for operation with the NCX-5 transceiver. NCX-A power supplies with serial numbers beginning with 44, 49, 57, 63, 69, or 72 must be modified before use with the NCX-5 transceiver. This modification may be easily made by connecting a 660 ohm 10 watt resistor in parallel with the two 330 ohm 10 watt resistors R-5 and R-6 in the NCX-A power supply. A partial schematic of the revised supply is shown on Figure # 1.
2.2 MOBILE MOUNTING:
A mounting bracket is supplied as standard equipment with the NCX-5 transceiver. For mobile operation, this bracket should be mounted under the automobile dashboard with two# 10, # 12, or 1/4 x 20 screws. For maximum stability, these screws should be located as far apart as possible in the mobile mounting bracket. A pair of large threaded knobs hold the transceiver directly to the bracket. These knobs permit rapid installation or removal of the transceiver from the mount. Mobile operation usually results in considerable vibration and shock. For maximum frequency stability of the NCX-5 transceiver, it is important that all mounting screws used to hold the cabinet to the chassis and panel assembly be in place and firmly tightened. In mobile use, the rubber feet may be removed from the bottom of the NCX-5.
2.3 MICROPHONE CONNECTIONS:
‘rhe microphone input of the NCX-5 is equipped with a three circuit jack providing a ground on the main shank of the three circuit plug. The audio output of a high-impedance ceramic or dynamic microphone (a crystal microphone may be used, but is not recommended for mobile operation) should be connected to the ring of the three circuit jack. If the microphone is equipped with a push-to-talk button, the push-to-talk button should be so wired that the

tip of the microphone plug is connected to the grounded shank of the plug when the push-to~alk button is pressed. The microphone push-to-talk button is connected to the -40 volt bias.
– CAUTION-
Accidental interchange of the wmng on the microphone plug will result in application of -40 volts to the microphone cartridge, which may damage the microphone.
‘rhe microphone input jack of the NCX-5 is equipped with a grounding contact so that no modulation of the transceiver is possible when the microphone plug is removed. Microphone connections are illustrated in figure No. 1. We recommend the use of a good quality, wide-range microphone, since all necessary restriction of audio bandwidth is accomplished in the NCX-5 crystal lattice filter. The P’I’T circuit of the microphone should be modified to permit VOX operation without depressing the PTT button. This may be done by bending one of the shorting contacts inside the microphone so that it does not short the microphone cartridge terminals when the button is released .
2.4 MOBILE SPEAKER INSTALLATION:
When the NCX-5 is installed in an automobile for use with the NCX-D supply, it will usually be most convenient to use the speaker of the regular automobile broadcast radio. Two leads should be brought out of the 12 terminal Jones plug at the rear of the NCX-5 (pins 5 and 7) and connected to the speaker through a DPDT switch mounted under the dash to allow choice of speaker operation with either the NCX-5 or the standard broadcast radio.
2.5 AUXILIARY RELAY CONTROL TERMINALS:
A pair of SPST relay terminals rated at 3 amperes current capacity is provided at the rear of the NCX-5 to allow control of accessory equipment such as the NCL-2000 amplifier. ‘rerminals are open during receive, closed during transmit.

3

INSTALLATION
FIGURE 1

=

..3
..5 4 7
REV IS1 0 N FOR USE WITH NCX-5 TRANSCE IV ER

I POWER SWITCH

~ POWER SWITCH

4 ~:.60YOLT

BIASo 6UA

5

SPEAKER HGROUN~ EATER

5 A

6 COUUON GROUND

7 SPEAKER

~ +280YOLT0200UA

+700YOLTo300UA

II
I

…l.

7

6

5

4

I I I

3

2

I I

POWER CONNECTIONS

MICROPHONE CONNECT.ONS

4

SECTION 3
OPERATION

3.1 TUNING PROCEDURES:
3.1.1 PRELIMINARY ADJUSTMENT
-CAUTION-
BEFORE ATTEMPTING TO OPERATE THE NCX-5 TRANSCEIVER, THE FOLLOWING PRELIMINARY CONNECTIONS SHOULD BE MADE: A SUITABLE ANTENNA OR DUMMY LOAD PRESENTING 40 TO 60 OHMS RESISTIVE LOAD IMPEDANCE SHOULD BE CONNECTED TO THE ANTENNA TERMINALS, A PROPER POWER CABLE SHOULD BE CONNECTED FROM THE POWER SUPPLY TO THE NCX-5 TRANSCEIVER, AND A MICROPHONE OR KEY SHOULD BE CONNECTED TO THE APPROPRIATE INPUT JACKS. THE FUNCTION SWITCH SHOULD REMAIN IN THE OFF POSITION WHILE THESE CONNECTIONS ARE BEING MADE.
1. Set front panel controls as follows:
MIC GAIN fully ccw (counterclockwise)
TRANSCEIVE VERNIER in OFF position (pushed in)
RF GAIN fully cw (clockwise)
AUDIO GAIN at 9 o’clock
BAND and MAIN TUNING to desired band and frequency
PA TUNE, PA LOAD, and EXCITER TUNE fully ccw
VOX-PTT switch in either position
MOX-OFF switch: OFF
SIDEBAND switch on desired sideband (usually LSB on the 80 and 40 meter bands, and USB on 20, 15, and 10 meter bands).

2. VOX GAIN, VOX DELAY, and MIC GAIN inside top cover should be set fully ccw, and CARRIER BALANCE at 12 o’clock.
3. BIAS adjust on rear panel should be set at 12 o’clock.
3.1.2 RECEIVER TUNE-UP (SSB)
1. Turn FUNCTION switch from OFF to SSB. After several seconds warm-up, the NCX-5 transmit-receive relay should close with an audible click. The NCX-5 is now in a receive condition on the selected band and frequency.
2. Adjust PA TUNE and EXCITER TUNE for maximum S-meter reading or background noise. This adjustment automatically sets up approximate transmit tuning since these controls are common for both transmitter and rece1ver.
3. Adjust AUDIO GAIN for comfortable listening level.
3.1.3 TRANSMITTER TUNE-UP (SSB )
-CAUTION –
DO NOT PROLONG TUNE-UP PROCEDURES MORE THAN 30 SECONDS AT A TIME IN ORDER TO PREVENT UNNECESSARY OVERHEATING OF COMPONENTS DURING OUT-OF-RESONANCE CONDITIONS. AFTER EXPERIENCE IS GAINED, TUNE-UP MAY BE ACCOMPLISHED IN A MATTER OF A FEW SECONDS.
1. Turn FUNCTION switch to TUNE and adjust EXCITER TUNE for maximum meter reading.
2. Adjust PA TUNE for minimum meter reading (dip) indicating proper tuning of the Pi network. Slowly rotate the PA LOAD control cw and dip meter reading with P.A. TUNE control until meter reads 300 MA.

5

3: Return FUNCTION switch to SSB. Push the MOX-OFF switch to the MOX position, and carefully rotate the CARRIER BALANCE control inside the top cover for minimum meter reading.
NOTE:
IF THIS IS THE FIRST TIME THAT THE NCX-5 HAS BEEN PLACED IN OPERATION, THE REAR PANEL BIAS CONTROL SHOULD BE ADJUSTED. THE NCX-5 IS IN TRANSMIT WITH THE MOX-OFF SWITCH IN THE MOX POSITION. THE REAR PANEL BIAS CONTROL SHOULD BE ADJUSTED UNTIL THE METER READS BETWEEN 50 AND 60 MA.
Return the NCX-5 to the receive condition (MOX switch OFF).
3.1.4 MOX OPERATION
1. The NCX-5 transceiver will now operate in both the transmit and receive modes using the MOX-OFF switch for transmit-receive control.
3.1.5 VOX OPERATION
1. Place the MOX-OFF switch in the OFF position.
2. Place front panel VOX-PTT switch to VOX.
3. Turn receiver AUDIO GAIN control (on the front panel) and VOX DELAY control (inside the top cover) completely ccw.
4. Rotate the VOX GAIN control (inside the top cover) until the relay just trips reliably while speaking into the microphone. Adjust VOX DELAY until VOX relay holds in for the desired time after speaking. These adjustments interact to a small degree, and it may be necessary to repeat all adjustments once or twice to optimize results.
Mobile VOX operation is quite easy and practical, but VOX GAIN and MIC GAIN should be adjusted for maximum close-talking to prevent car and wind noises from tripping the relay.
3.1.6 PTT OPERATION
1. Place the MOX-OFF switch in the OFF position.
2. Place the VOX-PTT switch to PTT.
3. Connect a suitable push-to-talk switch as shown in figure No. 1. The NCX-5 will operate in both the transmit and receive modes

by control from the external push-to-talk switch. The VOX DELAY control remains connected in the PTT mode and may be adjusted for fast or slow return to receive when the push-to-talk button is released.
3.1 .7 CW OPERATION
1. It is assumed that the NCX-5 has been set up for SSB operation and that it is now desired to operate CW.
2. Insert key plug in rear panel jack.
3. Turn FUNCTION switch to TUNE and adjust transmitter as for SSB operation.
4. Turn FUNCTION switch to CW, depress key, and adjust CARRIER BALANCE control (inside top cover) until meter reads 300 rna.
5. The NCX-5 is now tuned for CW operation and is ready for full break-in operation. When the key is depressed to start sending, the VOX relay will hold in until the operator stops sending, and then will automatically switch to receive. By adjusting the VOX DELAY control (inside the top cover), the operator may set the “hold-in” relay time to his liking.
3.1.8 AM OPERATION
1. It is asumed that the NCX-5 has been set up for SSB operation and that it is desired to operate AM.
2. Either MOX, VOX, or PTT operation should be selected.
3. Turn FUNCTION switch to TUNE, and adjust transmitter as for SSB operation.
4. Turn FUNCTION switch to AM, press MOX-OFF switch to MOX, and adjust CARRIER BALANCE until meter reads 150 rna.
5. Advance MIC GAIN until meter just flickers on voice peaks.
6. The NCX-5 is now adjusted for AM operation, and the AM detector is automatically in use.
3.2 DETAILED USE OF THE INDIVIDUAL CONTROLS:
The operating instructions in Section 3.1 of this manual enable rapid setup of the NCX-5 for SSB, AM, or CW transmission. Careful study of the following paragraphs will help you get the best performance from your NCX-5 transceiver.

6

3.2.1 MAIN TUNING CONTROL AND DIGITAL DIAL READOUT

T R. A N

NCX-6

The NCX-5 transceiver incorporates a digitaltype direct frequency readout to allow frequency adjustment to 1 Kc without interpolation between divisions. The VFO is accurate to 1 Kc, and it is read by adding the frequency in kilocycles shown on the counter dial to the frequency in megacycles shown on the BANDswitch. With the BANDswitch in the 14.0 Me position, the frequency as shown in the illustration above is 14.321 Me. If the BANDswitch were in the 3.5 Me position, for example, the above frequency would be 3.5 Me plus 321 Kc, or 3.821 Me.
To provide even greater resettability, the NCX-5 readout incorporates a fourth window, as shown above, calibrated in ten one-hundred-cycle divisions. The illustration above actually indicates that 321 Kc plus 200 cycles (321.2 Kc) should be added to the BANDswitch frequency.

3.2.2 DIAL SET
The dial of the NCX-5 may be adjusted to exact frequency, such as a 100 Kc marker from the optional plug-in XCU-27 calibrator, by tuning to the marker frequency in the receiver and then by pulling out the main tuning knob of the NCX-5 and turning the knob until the dial reading corresponds to the known marker frequency.

3.2.3 THE FUNCTION SWITCH

Note the various interlocking features of the

FUNCTION switch. In the SSB or AM positions of

the FUNCTION switch, either VOX, MOX, or PTT

operation may be used (see paragraphs 3.2.8 and

3.2.9). The rear p~nel

key_ j~ck

is disconnected in

the SSB or AM positions, thus allowing a key to be

left plugged into the NCX-5 at all times. Accidental

closing of the key will not trip the unit to transmit

if the ·FUNCTION switch is in either the SSB or

AM position. In the SSB position, the product de-

tector IS m use, and in the AM position, the diode detector is selected. Bias is applied to the carrier oscillator during AM receiving periods, thus silencing the beat frequency oscillator of the receiver.
If the front panel FUNCTION switch is in the CW position, the rear panel key jack is connected for automatic break-in operation. At the same time, the plate of the microphone preamplifier is grounded to prevent accidental modulation of the transmitted signal by a microphone connected to the NCX-5. During CW operation, the VOX-PT! switch can be in either the VOX or PTT positions without any effect on the operation of the transceiver. The slight audio “beep” which may be heard from the loudspeaker at the beginning of each keying cycle is the result of the extremely fast attack time of the break-in CW circuit which eliminates “clipping” the first dot.
Finally, in the TUNE position of the FUNCTION switch, the keying circuit is internally grounded, placing the NCX-5 in transmit condition. At the same time, one of the deflection electrodes of the 7360 balanced modulator tube is grounded, unbalancing the tube and providing more than normal drive to the final amplifier for tune-up. It is important to note that if the FUNCTION switch is placed in the TUNE position, and an antenna is connected to the NCX-5, full power transmission of a CW note will occur and can cause unwanted interference. Tune-up procedure should therefore be limited to as short a time as possible.

3.2.4. THE PA TUNE AND PA LOAD CONTROLS

Adjustment of the PA !UNE and PA LOAD controls is interdependent. For normal tune-up, the FUNCTION switch is placed in the TUNE position. The EXCITER TUNE control is set for maximum meter indication. The PA TUNE control is then set for minimum indication, indicating resonance of the Pi network. For a normal 40 to 60 ohm resistive antenna, the PA LOAD control should be rotated clockwise to increase the meter reading. As this is done, there will be some interaction with the PA TUNE control, and it will be necessary to slightly adjust PA ·TUNE for minimum meter indication. As the PA LOAD control is advanced, the minimum meter reading will increase. Proper loading for 200 watts peak input occurs at 300 rna (marked in red on the meter scale). This loading current should not be exceeded, since the Pi network design is such that additional power input from a 700 volt supply will not result in additional power output. Above 300 rna the efficiency of the NCX-5 final amplifier will be impaired, and no further output will be obtained.

Proper ope~atin

of any linear final amplifier

depends on proper idling current adjustment and on

sufficient drive for adequate peak plate current during

an off-resonance condition. The adjustment of the

bias setting of the NCX-5 final amplifier is discussed

7

in paragraph 3.1.3. Assuming this setting has been made for an idling current between 50 and 60 rna, it should be possible to obtain a momentary maximum
off-resonance piate current in ·excess of 350 rna when the PA TUNE control is rotated away from the point of minimum current. If 700 volts is being properly supplied to the plate circuit of the final amplifier, and the EXCITER TUNE control is properly adjusted, this off-resonance current should exceed 350 rna. If this current cannot be achieved, the cause should be found. Typical causes may include any of the following: improper Bias setting, improper EXCITER TUNE adjustment, low plate supply voltage to the final amplifier under full load condi-
tions, low driver B+, defective final amplifier tubes
or driver tube, or improper alignment of the exciter stages resulting in low driving signal.

As mentioned above, low plate supply voltage to the final amplifier will frequently result in difficulty in obtaining a suitable off-resonance current. The NCX-A power supply is rated to deliver 700 volts to the final amplifier with a 115 volt A.C. input. The NCX-D power supply is rated to deliver 700 volts to the plate circuit of the final amplifier with a 14.0 volt input to the power supply. If the A.C. line voltage or the mobile battery supply voltage is low, the power supply output wil be reduced. Under these conditions, an off-resonance plate current of less than 350 rna will probably occur. This will not impair the operation of the NCX-5 transceiver, provided that the PA LOAD control is not adjusted for excessive loading conditions. In no event should the LOAD control be advanced so that the plate current at the resonant dip exceeds 85% of the off-resonant plate current, which is noted by momentarily detuning the PA TUNE control.

In many instances an antenna load that is outside

the 40 to 60 ohm range of the Pi network will be

used with the NCX-5. Antennas presenting this type

of impedance should, if at all possible, be adjusted to

present a proper load at the NCX-5 antenna term-

nals. This can be done through the use of matching

ne~works

and, in many instances, by simply tailoring

the length of the antenna transmission line to modify .

its terminal impedance.

. Generally speaking, if the NCX-5 exhibits a resonant plate current in the dip in excess of 300 rna with the PA LOAD control rotated to its full counterclockwise position, the antenna load impedance is below 40 ohms. If, on the other hand, the resonant dip is still less than 300 rna with the PA LOAD control rotated to its full clockwise position, the antenna load impedance is above 60 ohms. It is possible to modify the Pi network output capacitors of the NCX-5 to take care of some misloading in these directions. With the PA housing. removed, a group of four mica capacitors will be seen just below the BANDswitch and connected between the BANDswitch and chassis. These capacitors, C-37 (3.5 Me),

C-38 (7 Me), C-39 (14 Me), and C-182 (21 Me) are, respectively, 1000, 470, 220, and 220 pF. They appear in parallel with the front panel PA LOAD control as shown on the schematic diagram and may be altered to extend the range of the Pi network. If the load impedance is too low, the capacitance should be increased. A good quality silver mica capacitor may be used for this purpose. It is advisable to use as large a case size on these capacitors as can be obtained.
There is of course some interaction of tuning between the PA LOAD control and the PA TUNE control. If load matching as described in the preceding paragraph is attempted, it is possible that the tuning of the PA TUNE control will be shifted to a point where this control will no longer cover the entire amateur band. In this event, it will be necessary to use external matching techniques. It is also possible that the antenna line will introduce an inductive or capacitive component to the NCX-5 antenna terminals. In this event, there may be also a shift of the PA TUNE control so that it will not tune over the entire amateur band. Again it will be necessary to alter the antenna impedance by means of an external matching network or correction of the antenna difficulties. SSB operation should not be attempted .unle~ the NCX-5 is properly matched and loaded because severe distortion can result with any improperly matched SSB transmitter or receiver.

3.2.5 CARRIER BALANCE CONTROL

During the tune-up (with the FUNCTION switch in the TUNE position) , one deflection electrode of the 7360 balanced modulator is grounded, creating complete carrier unbalance. Having accomplished proper transmitter tune-up, it is necessary to use the CARRIER BALANCE control to properly set up the NCX-5 transceiver for operation on SSB, AM, or CW operation.

For SSB operation, the NCX-5 is placed in a transmit condition either by the push-to-talk button or the MOX-OFF switch. In either event, the MIC GAIN control should be in full ccw position so that no audio modulation will occur. The CARRIER BALANCE control is then adjusted for minimum meter indication. This meter reading should be between 50 and 60 rna if the BIAS control is properly adjusted. When the CARRIER BALANCE control is properly set, it may be left in this position for all subsequent SSB operation. A more precise indication of CARRIER BALANCE control setting may be obtained either by using an oscilloscope connected to the antenna line or by listening to the carrier on a separate receiver. With proper carrier balance and tuning of the transceiver circuits, voltage on the antenna line should not exceed 0.5 volts peak-to-peak as indicated on the oscilloscope.

For AM operation, it is nec~3sary

to adjust the

CARRIER BALANCE control either cw or ccw

8

from the balance point until the meter indicates a final amplifier current of 150 rna. This corresponds to approximately 100 watts input to the final amplifier, thus assuring operation of the tubes within their plate dissipation rating.
Finally, for CW operation, it is necessary to adjust the CARRIER BALANCE control either cw or ccw from its zero setting until a meter indication of 300 rna is obtained. This assures an input to the final amplifier of 200 watts during key down transmit conditions of CW operation. Normal keying wave forms approximate a 50% duty cycle; that is, there is full input for about ~ of the time and no power for the remaining time. Thus the time-averaged input to the final amplifier is still approximately 100 watts, assuring conservative operation of the final amplifier.
3.2.6 CALIBRATOR CONTROLS
When the accessory XCU-27 100 Kc calibrator is plugged into the octal socket on the rear apron, 100 Kc crystal markers are available for precise calibration of the NCX-5. The calibrator is activated by means of a pull-push switch on the AUDIO GAIN control. The dial may then be set by following the instructions in paragraph 3.2.2.
3.2.7 S-METER ADJUSTMENT
Proper S-meter adjustment of the NCX-5 is obtained by disconnecting the antenna while the NCX-5 is set for SSB reception. With the RF GAIN fully clockwise (maximum gain ) , the S-meter adjustment (in front right corner of chassis ) is rotated until the meter indicates between 0 and 1 “S” units.
3.2.8 VOX-PTT SWITCH AND VOX C.IRCUIT ADJUSTMENTS
The VOX-PTT switch may be set to either mode, depending on preference and availability of a push-to-talk button on the microphone. Proper microphone jack connections are illustrated in figure No. 1.
Assuming that VOX operation is selected, the operator will find that the VOX GAIN and VOX DELAY control settings of the NCX-5 are remarkably free from interaction. The extreme VOX sensitivity available in the NCX-5 permits full anti-vox insertion at all times. As a result, no anti-vox control adjustment is required. With the VOX DELAY control fully ccw, VOX GAIN control is advanced slowly until the microphone just trips the NCX-5 to transmit with normal speech level. Mobile operation requires close talk to the microphone, since the high level of road, wind, and motor noises will otherwise tend to accidentally trip the VOX circuit. The VOX DELAY control is then adjusted for the desired release time.
It should be further noted that PTT and CW break-in operation are obtained through use of the

VOX circuit. However, the VOX GAIN control will have no effect on this operation and may· be left in any position. ·The VOX DELAY control is effective on both PTT and CW break-in operation and should be adjusted to the operator’s liking for delay at the end of the transmission.
3.2.9 THE MOX-OFF SWITCH
The MOX-OFF switch in the MOX (manual operation) position places the NCX-5 in the transmit mode, regardless of the position of the VOX-PTT switch or the FUNCTION switch. This position is useful for manual operation when the microphone is not equipped with a PTT switch. When the MOXOFF switch is returned to the OFF position, VOX or PTT operation may be selected by the VOX- PTT switch.
3.2.10 TRANSCEIVE VERNIER CONTROL
The TRANSCEIVE VERNIER control allows
± 5 Kc separation of the receive frequency from the
transmit frequency of the NCX-5. It is actuated by pulling the control out and rotating the knob to increase or decrease receiver frequency. The transmit frequency of the NCX-5 remains unchanged at all times-only the receiver frequency is affected by the TRANSCEIVE VERNIER. The NCX-5 TRANSCEIVE VERNIER will be found to be extremely useful in AM or CW QSO’s, as well as in SSB net operation. It allows the operator to tune to the desired AM or CW station with the VERNIER control pushed OFF, thus placing the transmit section of the NCX-5 on frequency. Then the TRANSCEIVE VERNIER can be pulled ON to offset receiver frequency enough to allow tuning of the station to the proper part of the filter passband for best copy without “walking” of the transmit signal.
To escape QRM during a QSO on SSB, the TRANSCEIVE VERNIER can be used to find a clear channel. Once a clear channel is found, the NCX-5 receiver is placed back on frequency simply by pushing the control IN, and arrangements may be made to QSY. The casual listener may also listen to two adjacent QSO’s by merely turning the TRANSCEIVE VERNIER control on and off and thereby instantly place the NCX-5 receiver on either frequency.
3.2.11 MIC GAIN CONTROL
After the NCX-5 has been set up by proper tuning of the final amplifier and exciter stages and the CARRIER BALANCE control has been properly set for carrier balance, the MIC GAIN control should be advanced until the meter reads between 100 and 125 rna average on speech content from the microphone. The single sideband audio information so developed has a rapidly varying energy content and the meter will rapidly fluctuate between the 40 to 50 rna idling current and the 100 to 125 rna average meter reading. Actual peak current is about 300 rna.

9

This fluctuation will be affected by the nature of the speech content and the individual voice. Generally speaking, the indication will be higher for long drawn out vowel sounds than it is for crisp consonant sounds.
Inclusion of an effective ALC circuit in the NCX-5 has diminished the importance of the microphone gain control. A MIC GAIN control has been provided because of the wide variety of microphones and large variation in output levels even of microphones of the same type. As the MIC GAIN control is rotated from the full ccw position, the current on voice peaks will increase to approximately 125 rna. As MIC GAIN is further increased, little additional change will be noted on the meter. The MIC GAIN control should be set slightly above the point where average current reaches the 125 rna level on the meter. Should the control be advanced well above this point, the ALC can no longer handle the drive level, and severe distortion may be generated.
For AM operation with the CARRIER BALANCE control set as described in paragraphs 3.1.8 and 3.2.5, there will be a steady meter reading of 150 rna. If the MIC GAIN control is advanced during speech, AM modulation of the final amplifier will occur. When the MIC GAIN control setting

reaches a point where the meter just indicates a slight flicker of speech peaks, modulation is 100%. Operation with the MIC GAIN control above this point should be avoided, since excessive drive will cause clipping of the modulation envelope, and this will result in unwanted spurious transmission outside of the passband of the NCX-5.
3.2.12 THE ‘TEN-METER SEGMENT SWITCH
If it is desired to operate on one of the 10-meter segments other than 28.5-29.0, selection of the appropriate 500 Kc segment is made by the 10-meter switch concentric with the PA TUNE control. The crystal for the segment from 28.5 to 29.0 is supplied with the NCX-5. If one of the other segments of the band is desired, the appropriate crystal must be plugged in. Sockets are near the existing crystal on the sub-chassis in the front right-hand corner of the NCX-5. The corresponding frequencies and crystals are: 28.0-28.5 Me segment- crystal frequency 24.5 Me; 29.0-29.5 Me segment-crystal frequency 25.5 Me ; and 29.5-30.0
Me segment-crystal frequency is 26 Me. These frequencies are also shown on the frequency chart under ”Theory of Operation.” Ten-meter segment crystals are available from the Service Department of the. National Radio Company.

BLOCK DIAGRAM
FIGURE 2

,

D R I V ER

I ~1 …1

2ND MIXER

1ST MIXER

BUFFER

VFO

I I
L – – – ——- – —, I I
I
· I
I 1sr 11F

S· METER AMPL

LEGEND ·

=

RECEIVE PATH

– – – – TRANSMIT PATH

– – CONTROL PATH
:== TRANSMIT AND RECEIVE PATH

PRODUCT DETECTOR

KEY

I

I

MIC
@-~

1liil. ~SPECH ~AMPL

MICROPHONE PRE-AMPL

10

SECTION 4
THEORY OF OPERATION

4.1 GENERAL:
The NCX-5 transceiver, designed to cover the 80 through 10 meter amateur bands, combines a double conversion superheterodyne receiver and single sideband transmitter, both employing a common crystal lattice filter. The final Pi network, mixer and driver tuning ·circuits of the transmitter also serve as RF circuits for the receiver. The carrier oscillator and VFO are common to the receiver and transmitter circuits while the receiver first lF stage is used as a low level amplifier in the transmitter-exciter function. The use of common filter and RF input components results in an extremely sensitive and image-free, selective receiver and in a high quality, low distortion SSB transmitter.
The operation of the NCX-5 is best understood by reference to the block diagram, figure 2, and the frequency chart, figure 3.
4.2 THE TRANSMITTER:
The transmit signal path of the NCX-5 is indicated on the block diagram by a dashed line starting at the mike jack and carrier oscillator. The microphone input circuit is designed for high-impedance dynamic or crystal microphones and provides for a push-to-talk microphone circuit. The microphone is connected directly to the grid of the pentode section of a 6GH8 (V8A) tube which operates as a preamplifier. The signal is then fed through the microphone gain control to one triode section of the 12AT7 (V6A) speech amplifier. The plate circuit of this speech amplifier is coupled to one of the deflection electrodes of the 7360 (V10) balanced modulator.
A 12AU7 (V7) tube is used for the two carrier oscillators. Each crystal is permanently connected to its triode section, and sideband switching is accomplished by applying a negative bias to the section to be turned off. The carrier signal appears across a common resistive plate load and is fed to the grid of the 7360 balanced modulator tube V-10. A D .C. network containing the carrier balancing control potentiometer is connected to the deflection electrodes of the 7360. In addition, a trimmer provides phase balance for maximum carrier suppression. The balanced primary winding is coupled to a single-ended secondary which serves as the input source for an eight-pole crystal lattice filter.

The crystal lattice filter is resistance terminated and coupled directly to the grid of the 12BA6 {V15) first IF stage. The single-tuned plate circuit is coupled to the grid of the 12BE6 (V3) first transmit mixer.
The VFO uses a 2N706 (Q1) NPN transistor oscillator and a 2N2188 (Q2) PNP transistor buffer. All biasing resistors and tank circuit capacitors are chosen for low noise and temperature characteristics. Power for the VFO circuits is double-regulated by
a zener diode regulator fed from the regulated + 150
volt bus. The result is a VFO circuit with a total drift from “turn on” of less than 100 cycles in any ·tenminute period, including variations of external supply voltage and ambient temperature. The main tuning capacitor is completely linear with an accuracy of 1 Kc at any point within the 500 Kc tuning range. Output from the VFO is taken from the collector of the 2N2188 (Q2) and fed to the oscillator grid of the 12BE6 (V3) first transmit mixer.
The output from the first transmit mixer (V3) is always in the 3.5 to 4.0 Me band. This signal is fed through a bandpass double-tuned circuit to the grid of the pentode section of the 6KE8 (V4B) second transmit mixer. The triode section of the 6KE8 is used as a crystal oscillator which feeds both the second transmit mixer and the first receive mixer.
The plate circuit of the second transmit mixer is single-tuned and feeds the grid of the 6GK6 (V5) driver. The single-tuned plate circuit of the driver feeds the grid of the final amplifier. The coils in the plate circuits of the transmit mixer and driver are band switched for the 80, 40, 20, 15, and 10 meter amateur bands. The tuning gang is tracked so that exciter tuning can be accomplished with only one controL The gains of the transmit mixer and driver are such that a driving signal in excess of 100 volts can be obtained at the grid of the final amplifier, thus assuring linear operation of the exciter to well above the level necessary for proper drive.
The final amplifier employs a pair of 6GJ5 (V1 and V2) tubes operating in parallel. A bias control on the rear apron sets proper idling current. The plates of the 6GJ5 final amplifier are coupled to a high-efficiency Pi network. The band switch selects proper inductance, tuning and load capacitance to match a 40 to 60 ohm resistive load over the entire 80, 40, 20, 15, and 10 meter amateur bands. The Pi network is designed for continuous operation at

11

a power level of 200 watts input. A small adjustable capacitor coupled from the plate of the 6GJ5 final amplifier to the partially by-passed return of the final grid circuit coils (driver plate coils) provides neutralization. When the final amplifier is properly neutralized, maximum output on a matched antenna will occur at the point of plate current dip as indicated on the meter.
An effective ALC (automatic level control) circuit is included. If the final amplifier grids are overdriven on voice peaks, the grids will actually see a driving signal positive with respect to the cathodes, and grid current will result. This current will cause a negative voltage change on the bias circuit. The resulting audio signal on the bias circuit is capacitively coupled to a voltage-doubling rectifier. This rectifier will provide a negative D.C output which is coupled to the grid return of the 12BA6 (V15) first IF amplifier. When overdrive occurs, the gain of the first IF amplifier is reduced, resulting in less driving signal at the final amplifier. Charging takes place rapidly . from the low-impedance bias source through the rectifying diodes, but the negative ALC voltage cannot discharge through the reverse biased diodes, resulting in a fast attack-slow release action. A gating diode prevents cross connection of the ALC and AGC circuits at the common IF grid return point. The ALC circuit will provide automatic level control for input signal variations of more than 10 db., and makes the setting of the MIC GAIN control quite noncritical. In addition, sudden changes in voice level or disturbing background noises are all instantly controlled without overdrive and distortion of the NCX-5 transmitter.
4.3 THE RECEIVER:
The receiver circuits are indicated by the double solid lines in the block diagram. The receiver RF circuits are common to the transmitter RF circuits. The high-impedance point of the transmitter Pi network is capacitively coupled to the grid of a 6BZ6 (Vll) RF amplifier. The tuned circuits at the plate of the transmit driver and plate of the transmit mixer are the input and output circuits of the 12BA& (V12) second RF amplifier. They provide for receiver RF selectivity and common receiver-transmitter tuning. The output from the second RF amplifier is coupled to the signal grid of the first receive mixer 12BE6 (V13). The oscillator grid is fed from the 6KE8 (V4A) crystal oscillator. The plate of this mixer is coupled to the signal grid of the 12BE6 (Vl4) second receive mixer. VFO signal is coupled to the ·oscillator grid of this mixer. The plate circuit of the· second receive mixer is connected directly across the secondary of the balanced modulator transformer which serves as the input coil to the crystal lattice filter.
The output of the crystal lattice filter, as in the transmitter, couples to the input of a three stage single-tuned IF amplifier operating at approximately 6.02 MC. The detectors and AGC circuits are fed

through separate voltage dividers. The product detector employs one triode of the 12AX7 tube (V18A) with the signal from one IF voltage divider fed to the grid. A BFO signal is coupled from the crystal controlled 12AU7 (V7) carrier oscillator to the cathode of the product detector, and the resulting audio signal is obtained across a resistive load in the plate circuit. For AM operation, a separate diode detector is connected.
The output from the detectors is coupled to the audio gain control, and then to the grid of the remaining triode section of the 12AX7 (V18) tube functioning as a grid-leak biased, first audio amplifier. The plate circuit is coupled to the grid of the 6AQ5 (V19) audio output stage. The audio output stage feeds the output transformer having a 3.2 ohm secondary. This output signal· is also available at the phone jack. The low-impedance nature of the phone jack feed permits use of either high- or low-impedance phones.
A secondary feed is obtained from the plate circuit of the last IF amplifier and is fed to a voltagedoubling AGC rectifier. The low-impedance driving source provides a rapid charge of the AGC bus. When the signal disappears, the negative AGC bus cannot discharge through the diodes, which provides a long release time, thus giving the AGC a very effective, fast-attack, slow-release action. The AGC is fed to the grid of the remaining half of the 12AT7 (V6B ) S-meter amplifier. AGC is connected to the grid returns of the RF stage, second IF stage, and through the gating diode to the first IF stage for control.
4.4 THE VOX CIRCUITS:
Before considering the switching operations, we must first discuss the VOX circuits.
The signal which trips the relay from receive to transmit is derived from two sources. The first source is the VOX signal which is picked up after the microphone preamplifier and separately amplified in a two stage amplifier consisting of V9A and V9B (12AU7). The other signal is derived from the plate of the audio output tube and is called the ANTIVOX signal.
Both signals are rectified, the VOX signal so as to make a negative voltage, the ANTI-VOX signal making a positive voltage. The two D.C. voltages are applied in series to the grid of the relay control tube. The circuit constants in the VOX and ANTIVOX detectors are arranged so that the D.C. voltage derived from the ANTI-VOX detector is always larger than the voltage generated in the VOX channel from loudspeaker information.
Additional information entering the microphone is amplified through the VOX amplifier and will develop enough negative voltage at the grid of the relay tube to let the relay fall off and place the circuit into transmit position.

12

The VOX and ANTI-VOX detector time constants are so arranged that the circuits will drive the relay tube grid negative in a very short time. At the end of transmision, the relay control signal cannot discharge backwards through the diodes. The discharge time is controlled by R7, the DELAY control which can be set from a fraction of a second to several seconds. This circuit is also used in the CW position and will be discussed later·.
4.5 THE FUNCTION SWITCHES:
The following paragraphs describe the operation of the various switching circuits with the FUNCTION switch in all possible positions.
4.5.1 FUNCTION SWITCH OFF
In this position the FUNCTION switch inter· rupts the primary power, either directly in case of the NCX-A power supply or through a remote relay in the NCX-D 12 volt D.C. supply. The position of all other switches becomes irrelevant.
4.5.2 FUNCTION SWITCH SSB
In this position the following circuits are set up: The VOX-PTT switch, the product detector, and the microphone amplifier are connected into the circuitry. The key jack is disconnected to prevent accidental keying.
Now three different types of operation are possible:
4.5.2.1 VOX OPERATION
VOX switch in VOX position and the MOXOFF switch in OFF position. In this combination the VOX and MOX switches ground the keying diode. Voice information from the microphone will override the ANTI-VOX, as described before, tripping the relay. The relay will transfer B+ to the final and other transmitting tubes. Negative bias is removed from various transmitting tubes and applied to receiving tubes and the first audio amplifier for quiet switch over. At the end of transmission and after the preset DELAY, the relay will pull in again, placing the set in receiving condition.
4.5.2.2 PUSH-TO-TALK OPERATION
VOX-PTT switch on PTT, MOX-OFF switch on OFF position. The output of the VOX amplifier is now shorted to ground, and the push-to-talk contact is connected across the transmit bias line. When the push-to-talk contact is pushed, the bias line ( 135) is grounded, which removes the disabling bias from transmitting tubes. The bias is also removed from the

first transmit mixer. The screen of this ·miXer tube V3 (12BE6) will now draw current, causing a reduction of screen voltage. A voltage divider connected from this screen to the -80 bias line will develop a negative signal which is tied through the VOX-PTT and the MOX switch to the keying and PTT diode. The keying and PTT diode feeds the grid of the relay tube. The relay tube will be biased off, the relay falls out, and the set is in transmitting position.
The negative signal developed at the first transmit mixer screen is also fed to the product detector and audio output amplifier for quiet switching.
On release of the push-to-talk button, the negative bias reappears on the transmit tubes. The grid of the relay control tube returns to normal, the relay pulls in, and receiving conditions are restored.
4.5.2.3 MOX OPERATION
With the MOX switch in the MOX position, the transmitter bias line (135) is grounded directly. Switching occurs as with PUSH-TO-TALK operation. Returning the MOX switch to OFF will turn the transmitter off and put the set into receive condition.
4.5.3 FUNCTION SWITCH IN AM POSITION
The AM position of the FUNCTION switch transfers the input of the audio amplifier to the output of the AM detector. Also, disabling bias is applied to the carrier oscillator in use during receiving conditions to silence the BFO signal.
VOX, PTT, MOX operation functions now operate in the same manner as described under SSB (4.5.2).
4.5.4 FUNCTION SWITCH IN CW POSITION
In this position the FUNCTION switch will disconnect the VOX-PTT switch, ground the plate of the microphone preamplifier to prevent any speech· information from coming through, connect the input of the audio amplifier to the output of the product detector, and connect the KEY jack to the transmitter bias line.
When the key is depressed the first time, the transmitter bias line (135 ) is grounded, placing the transmitter tubes and the first transmit mixer into operation. As described above under SSB operation, PUSH-TO-TALK (paragraph 4.5.2.2), the screen divider of the first transmit mixer will now actuate the relay tube through the keying diode. The relay will fall out, placing the NCX-5 into the transmitting position. From here on in, further keying is done by grid-block method, since the DELAY on the relay control tube will hold the transmit relay in for a predetermined time. Effective break-in keying is therefore realized. The VOX-PTT circuits are dis-

13

abled so that the microphone can be left in its jack. The MOX switch, however, will still actuate the transmitter.
4.5.5 FUNCTION SWITCH IN ‘rUNE POSITION
In this position the FUNCTION switch will ground the transmitter bias line, placing the transmitter into operation, as described under “SSB-PTT Operation” (paragraph 4.5.2.2) and ground one of the balanced modulator deflection plates, providing a strong signal through the system. ‘rhe MOX, VOX, PTT, and key circuits are disabled and have no influence on the tuning procedure.
4.6 RELAY FUNCTIONS:
In the foregoing discussion, the exact nature of the relay switching was not described. The six-pole double-throw relay is actuated by the plate current of the 6GH8 relay tube V8B. The NCX-5 is placed in a transmit condition when the relay is de-energized.
The first set of contacts, 5, 6, and 7, transfers
+ 220 volts between transmit and receiving functions.

Contacts 8, 9, and 10 transfer the bias on the varactor diode in the VFO. This varactor is actuated by a bias depending on the setting and switching of the TRANSCEIVE VERNIER control during receiving periods and by a fixed bias during transmitting periods.
Contacts 11 and 12 are closed during transmit and are brought out on the rear apron of the NCX-5 for operation of the NCL-2000 linear amplifier.
Contacts 14, 15, and 16 operate as follows: The relay arm, contact 15, grounds the AGC line of the receiver at contact 14 to prevent excessive AGC build-up during transmit periods and to assure a prompt recovery of the receiver when required. Contact 15 grounds the screens of the final amplifier at contact 16, during receiving periods.
Contacts 17, 18, and 19 also are grounding contacts: the arm, contact 18 connects the meter at contact 17 to read the final cathode current during transmit periods; contact 19, grounded during receiving periods, is connected to the accessory socket for operation of the external VX-501 console.
Contacts 20, 21, and 22 ground the bias line either for receive or transmit, placing the appropriate tubes into operation as desired.

Final Output Transmit Driver Second Transmit Mixer Receiver RF Amplifier Receiver Mixer Input
Crystal Osc.
First Transmit Mixer Output
First Receive Mixer Output

VFO

USB LSB

Carrier Osc. Second Receive
Mixer Output
Receiver IF

USB LSB

3.5-4 7-7.5 14-14.5 21-21.5 28-28.5 28.5-29 29-29.5 29.5-30

None

11

18

25

24.5

25

25.5

26

3.5-4 4–3.5 4–3.5 4–3.5 3.5-4 3.5-4 3.5-4 3.5-4

9.5236 10.02 10.0236 9.52

10.02 9.52

10.02 9.52

9.5236 9.5236 9.5236 9.5236 10.0236 10.0236 10.0236 10.0236

9.52 10.02

10.0236 10.0236 10.0236 9.52 9.5236 9.5236 9.5236 10.02

9.52 10.02

9.52 10.02

9.52 10.02

6.0236 6.02

6.02

6.02

6.0236 6.0236 6.0236 6.0236

6.02

6.0236 6.0236 6.0236 6.02

6.02

6.02

6.02

FREQUENCY CHART
FIGURE 3

14

SECTION 5
NCX-5 TEST AND ALIGNMENT

NOTE:
TEST AND ALIGNMENT OF THE NCX-5 SHOULD ONLY BE PERFORMED BY COMPETENT, QUALIFIED PERSONNEL.
5.1 EQUIPMENT REQUIRED:
1. Signal generator providing output at the following frequencies: 6.0218 Me, 3.5 Me, 4 Me, 7 Me, 7.3 Me, 14.0 Me, 14.4 Me, 21.0 Me, 21.5 Me, 28.0 Me, 28.5 Me, 29 Me, 29.5 Me.
2. Vacuum tube voltmeter (VTVM).
3. Standard output meter.
4. Sweep generator capable of sweeping at approximately 60 cycles per second over a frequency range from approximately 3 to 4.5 Me.
5. High-frequency oscilloscope covering the range from DC to 30 Me with a maximum sensitivity of 50 mv per centimeter or better and a low capacity input probe (Tektronix type 545 with type L preamplifier or equivalent).
6. External receiver capable of receiving at 9.72 Me.
7. 50 ohm dummy load with calibrated output meter covering the frequency range from 3.5 to 30 Me. (A high frequency vacuum tube voltmeter with a 100 volt full scale range may be substituted for the calibrated output power meter.)
8. Power supply capable of supplying + 700 volts at 300 rna, +280 volts at 200 rna and – 80 volts at 6 rna.
9. 1000 cycle audio generator with an output level of 10 mv.
10. High quality microphone equipped with push-to-talk button.
11. Transmitting key.
12. Suitable alignment tools for adjustment of coils and capacitors.
13. XCU-27 crystal calibrator.

5.2 INITIAL CONTROL SETTINGS:

FRONT PANEL

RF and AF GAIN .. . ……….. . FUNCTION Switch ………. . . PA TUNE ………. . ……… . PA LOAD and EXCITER TUNE BANDSWITCH .. … .. …….. . TRANSCEIVE VERNIER ….. . SIDEBAND Switch …… . ….. . 10-METER Switch …….. .. … . MOX-OFF Switch . .. ……. . .. . VOX-PTT Switch . . . … ……. .

Full cw OFF Full cw Full ccw 3.5 Me OFF USB 28.5 Me OFF PTT

BIAS

REAR PANEL

Mid-range

INSIDE TOP COVER

MIC GAIN . …. ………….. . CARRIER BALANCE …… . .. . VOX GAIN . …………. . … . VOX DELAY . ……………. .

Full ccw Full cw or ccw Full ccw Full ccw

Power Connections:
Connect the power supply with the 700 volt output turned off. The heater wire connecting the two 6GJ5 sockets should be removed.

5.3 IF ALIGNMENT PROCEDURE:
Turn the FUNCTION switch to SSE. In a few seconds the relay should close, indicating that the NCX-5 is in a receive condition.
Connect the audio output meter to the speaker leads. This may be conveniently done by plugging the audio output meter into the phone jack. Connect the signal generator through a 1000 pF capacitor to the grid (Pin 7) of the 12BE6 (V-14) second receive mixer. Set the signal generator for output at 6.0218 Me. A 1 to 2Kc beat note should be heard. Align the slugs of the first, second, and third IF transformers (T-4, T-5, and T-6), as well as the bottom slug of the balanced modulator transformer (T-1) for maximum output, being careful to avoid overload of the receiving channel. The signal generator output should be reduced throughout this alignment procedure so that an output of 100 mw is never exceeded.

15

5.4 BALANCED MODULATOR ADJUSTMENT:
Connect the high-frequency oscilloscope to the grid (Pin 1) of the first IF amplifier 12BA6 (V-15). Place the MOX-OFF switch in MOX position. The relay in the NCX-5 should open, placing the unit in a transmit condition. Adjust the top and bottom slug of the balanced modulator transformer (T-1) for maximum indication on the scope. Carefully adjust CARRIER BALANCE control for minimum indication on· the scope. This should occur near mid-range of the control. Return the CARRIER BALANCE control to full cw or ccw. If there is no indication at this point, the carrier oscilloscope trimmer (C-6) corresponding to the upper sideband crystal at 6.0234 Me may be adjusted to insure that the carrier oscillator is functioning.
5.5 CARRIER OSCILLATOR SETTING:
With connections set as for balanced modulator adjustment, adjust (C-6) corresponding to the 6.0234 Me crystal until the signal level is 0.2 volts peak-topeak as indicated on the oscilloscope.
Set the SIDEBAND switch to LSB. Adjust (C-5) corresponding to the 6.020 Me crystal until the signal level is 0.2 volts peak-to-peak as indicated on the oscilloscope.
Return the SIDEBAND switch to USB and remove the oscilloscope connection. Return MOX-OFF switch to OFF.
5.6 TRANSMITTER BANDPASS TUNING:
Connect the sweep generator to the signal grid (Pin 7) of the first transmit mixer 12BE6 (V-3) . Connect the oscilloscope to the junction of C-134, R-76, and the cable feeding the grid of the second transmit mixer. Press the MOX-OFF switch to MOX. The CARRIER BALANCE control may be adjusted for minimum carrier to avoid unwanted oscilloscope indications. Adjust the top and bottom slugs of the transmit bandpass coil (T-2 ) for maximum display amplitude and proper response. The 3.5 and 4.0 Me outputs of the signal generator may be used as marker frequencies. When properly aligned, the oscilloscope display should be as indicated.

3.5Mc MARKER3 TO 6db
FROM PEAK

4.0Mc -MARKER
3 TO 6db FROM PEAK

Return MOX-OFF switch to OFF and disconnect oscilloscope and sweep generator leads.

5.7· RECEIVER BANDPASS TUNING:
Connect the sweep generator to the signal grid (Pin 7) of the first receive mixer 12BE6 (V-13) . Connect the oscilloscope to the signal grid (Pin 7) of the second receive mixer 12BE6 (V-14) . Adjust the top and bottom slugs of the receiver bandpass coil (T-3) for maximum display amplitude and proper response similar to that obtained for the transmit bandpass coil. Disconnect the oscilloscope and sweep generator connections.
5.8 VFO FREQUENCY ALIGNMENT:
Connect the high frequency signal generator to the signal grid (Pin 7) of the first transmit mixer 12BE6 (V-13). Preset the sideband switching trimmer (C-16) and the temperature compensating trimmer (C-18) to mid-range. Set the signal generator frequency to 4 Me. Adjust the VFO coil (L-27) for zero beat. Set the generator input to 3.5 Me and tune the main tuning dial toward 3.5 Me. A beat note should be obtained in the region of 3.5 Me on the dial. If this beat note occurs at a dial setting above 3.5 Me, the VFO trimmer (C-1 7″) sliould be turned to reduce the capacity. If the beat note occurs below 3.5 Me on the dial, increase the trimmer capacity. Return the signal generator and main tuning dial to 4 Me. Reset the VFO coil slug for zero beat and again observe the location of the beat note near 3.5 Me with the signal generator set to 3.5 Me. This procedure should be repeated until the 3.5 Me beat note and the 4.0 Me beat note occur within 500 cycles of the dial markings.
5.9 VFO LINEARITY ADJUSTMENT:
A special linearity adjustment (consisting of two segmented plates and a stator) is incorporated in the rear section of the NCX-5 VFO capacitor. After adjustment of the VFO frequency at 4.0 and 3.5 Me, it will be necessary to set the VFO linearity.
Insert the crystal calibrator into the crystal calibrator socket. With the crystal calibrator turned on and set for 100 Kc markers, it should be possible to obtain a zero beat at the 3.5 and 4.0 Me points which have previously been set. The main tuning should now be adjusted to 3.9, 3.8, 3.7, and 3.6 Me. At each of these points zero beat should occur within +500 cycles of the exact dial frequency. If necessary, one (or both) of the segmented adjusting plates should be bent as required to achieve proper calibration. If the indicated frequency is too low at the zero beat point, one or both of the plates should be moved toward the stator. If the indicated dial reading at zero beat is too high, the plate should be moved away from the stator. It is important that this linearity correction be made on a gradual basis. The entire correction at any one point should not be made with a single segment of the correction plate. When properly aligned, the corrector segments will lie in a smooth curve.

16

5.10 VFO SIDEBAND SWITCHING ADJUSTMENT:
Set the main tuning to zero beat at 3.8 Me, rotate the sideband selector switch to LSB. The frequency obtained should still be zero beat. If it is not, set the sideband trimmer (C-16) for zero beat. As the sideband selector switch is rotated from LSB to USB, there should be no change of frequency. There is a small interaction of this adjustment with the VFO alignment. The VFO alignment should be readjusted if any error is introduced.
5.11 TEMPERATURE COMPENSATING
ADJUSTMENT:
During alignment of the NCX-5, its VFO should be checked. If drift is excessive, the temperature compensating capacitor should be adjusted to provide greater or less compensation. Drift towards a lower dial reading on 80 meters indicates excessive temperature compensation and the compensating trimmer (C-18) should be turned to reduce capacity. A drift toward a higher dial reading indicates insufficient compensation and the trimmer should be turned for greater capacity. Adjustment of the compensating trimmer will change the VFO frequency. Complete realignment of the VFO can be avoided by the following procedures: Set the NCX-5 to zero beat at the 3.8 Me dial setting. Adjust the compensating trimmer as required and immediately adjust the VFO trimmer (C-17) to return the NCX-5 to zero beat. If this procedure is carefully followed, the dial calibration should not be seriously affected. If a major correction has been made, the dial calibration should be checked and the alignment of the preceding sections should be repeated if necessary. Disconnect the signal generator leads from the NCX-5.
5.12 TRANSMIT MIXER AND DRIVER ALIGNMENT:
Connect the high-frequency oscilloscope to the junction of C-46, R-42, and the grids of the 6GJ5 final amplifier. Set the BAND switch to 3.5 Me and the FUNCTION switch to TUNE. The relay should again drop out, indicating that the unit has been placed in a transmit condition. Set the main tuning dial to 3..750 Me and the EXCITER control to 5. Adjust the 80 meter mixer coil (L-10) and the 80 meter driver coil (L-5) slugs for maximum indication on the oscilloscope. When the slugs are properly adjusted, the peak-to-peak output voltage on the oscilloscope should exceed 130 volts.
Set the BAND switch to 7.0 Me and the EXCITER TUNE control to 6. Repeat the above procedure at 7.300 Me while adjusting the 40 meter mixer coil (L-9) and the 40 meter driver coil (L-4) . An output of more than 130 volts peak-to-peak must be indicated on the oscilloscope.

At this point a ripple will appear on the oscilloscope pattern. Adjust the harmonic trap (L-29) to minimize this ripple. After this adjustment is made, there will be some interaction with the tuning of the 40 meter mixer coil (L-9) which must be readjusted for maximum amplitude. Repeat these adjustments until minimum ripple and maximum amplitude are obtained simultaneously. The setting of the harmonic trap may be checked by removing the 11 Me crystal in the high-frequency oscillator circuit. When the crystal is removed, there should be a large drop in the amplitude of the oscilloscope display. If there is no such drop, the harmonic trap has been mistune4 and the slug should be withdrawn from the coil and the above alignment procedure repeated on the proper trap frequency.
Set the BAND switch to 14.0 Me and the EXCITER TUNE control to 3. Repeat the above procedure at 14.250 Me while adjusting the 20 meter mixer coil (L-8) and the 20 meter driver coil (L-3) .
Set the BAND switch to 21.0 Me and the EXCITER TUNE control to 7. Repeat the above procedure at 21.250 Me while adjusting the 15 meter mixer coil (L-7 ) and the 15 meter driver coil (L-2).
Set the BAND switch to 28.5 Me and the EXCITER TUNE control to 7. Repeat the above procedure at 28.750 Me while adjusting the 10 meter mixer coil (L-6) and the 10 meter driver coil (L-1).
5.13 FINAL AMPLIFIER PRELIMINARY ADJUSTMENT (10 METER):
The NCX-5 construction does not provide for any alignment of the final amplifier. It is necessary at this time to check the final amplifier for proper operation at the high and low ends of all bands. In addition, it is necessary to make a slight final adjustment on the driver plate coils and on the neutralizing capacitor. These checks should be made in the following sequence: Connect the heater wire between the 6GJ5 sockets. Place the FUNCTION switch in the OW position and allow approximately 30 seconds for warm-up of the final amplifier tubes.
-CAUTION-
UP UNTIL THIS TIME, THERE HAS BEEN NO POWER APPLIED TO THE FINAL AMPLIFIER. ALL CIRCUITS WHICH HAVE BEEN OPERATING AND WHICH HAVE BEEN TESTED ARE LOW LEVEL CIRCUITS USING VOLTAGES AND POWER NORMALLY ENCOUNTERED IN DAY-TO-DAY RECEIVER WORK. FROM HERE ON, VOLTAGES AND CURRENTS MAY BE ENCOUNTERED WHICH ARE
DANGEROUS TO PERSONNEL AND TO THE
TEST EQUIPMENT AND THE UNIT UNDER TEST. IT IS ESSENTIAL TO BE SURE THAT NO PIECE OF TEST EQUIPMENT BE MISCONNECTED INTENTIONALLY OR ACCIDENTALLY TO THE NCX-5. IT IS FURTHER

17

IMPORTANT THAT PERSONNEL BE CAUTIONED AGAINST CARELESS HANDLING WHICH MAY RESULT IN CONTACT WITH DANGEROUS VOLTAGES. IT IS FURTHER IMPORTANT THAT THE NCX-5 NOT BE PLACED INTO A .TRANSMITTING CONDITION WITHOUT PROPER TUNING, SINCE DAMAGE MAY RAPIDLY RESULT TO THE NCX-5. IN A NUMBER OF THE FOLLOWING TESTS ‘rHE TRANSMITTER WILL BE OPERATED AT FULL POWER OUTPUT. IF MISINDICATIONS ARE OBTAINED, OR IF THE TEST IS NO’r COMPLETED WITHIN A PERIOD OF 15 SECONDS, OR IF THE UNIT IS NOT TUNED UP WITHIN A PERIOD OF 15 SECONDS, IT IS IMPORTANT THAT THE UNIT BE RETURNED ‘rO A RECEIVING CONDITION. OTHERWISE, SERIOUS AND PERMANENT DAMAGE CAN BE DONE TO THE FINAL AMPLIFIER TUBES AND COMPONENTS IN THE FINAL OUTPU’r CIRCUIT.
Disconnect all test equipment from the NCX-5. Attach the 50 ohm dummy load with calibrated output meter to the NCX-5 antenna terminals. With a D.C. voltmeter, set the bias at the grid of the final amplifier for maximum negative voltage. With the BAND switch still on the 28.5 Me band, set the main tuning dial to 28.75 Me. Now tum the FUNCTION switch to TUNE and rapidly peak the EXCITER TUNE for maximum meter reading on the combination S-meter and cathode current meter. Adjust the 10 meter driver plate coil (L-1) for maximum meter reading while slowly rocking the EXCITER TUNE control. This will correct for the presence of the oscilloscope probe in the previous setting. Now rotate the PA TUNE control and observe whether a dip occurs in the plate current reading.
Note the power output reporded by the power output meter. This power output should exceed 100 watts at all frequencies providing the PA LOAD control is adjusted so that the final amplifier draws 300 rna. With the PA TUNE control set for a plate current dip, the PA LOAD control is slowly rotated in a clockwise direction. As the PA LOAD control i~ advanced, it will be necessary to slightly retune the PA TUNE control to stay in the dip. Continue this process until the minimum reading in the dip corresponds to 300 rna on the meter.
5.14 NEUTRALIZING CAPACITOR:
With the FUNCTION switch in the TUNE position, rotate the PA TUNE control to either side of the resonant point and observe the plate current meter. It is necessary that the off resonance current exceed 350 rna. Having noted the off resonance plate current, retune the PA TUNE control to the plate current dip at 300 rna and observe the power output. It should exceed 100 watts. Carefully rotate the PA

TUNE control to either side of the dip and observe whether the power output rises or falls. With a proper setting of the neutralizing capacitor, the power output should fall to either side of the dip. If the power output actually rises as the tuning control is tuned away from the dip, it will be necessary to adjust the neutralizing capacitor. ‘rhis can be quickly done on a trial and error basis by rotating the neutralizing capacitor and observing whether maximum power output occurs at the plate current dip. As proper neutralization is achieved, maximum power output will occur at minimum plate current. Return the FUNCTION switch to CW.

5.15 FINAL AMPLIFIER PRELIMINARY ADJUSTMENT . (80-15 METERS):
Set the BAND switch to 21 Me and the main tuning dial to 21.250 Me. Tum the FUNCTION switch to TUNE and rapidly peak the EXCITER TUNE for maximum meter reading. Adjust the 15 meter driver plate coil (L-2) for maximum meter reading while slowly rocking the EXCITER TUNE control. This will correct for the presence of the oscilloscope probe in previous tests. Now rotate the PA TUNE control and observe whether a dip appears in the reading. Advance the PA LOAD in a clockwise direction and slightly retune the PA TUNE control to stay in dip. Continue this process until the minimum meter reading in the dip corresponds to 300 rna. The power output should exceed 100 watts and proper neutralization should be observed.
Repeat this procedure at the following BAND switch and tuning settings, in each case adjusting the proper driver coil for maximum meter indication while rocking the EXCITER TUNE control.

MAIN

BANDSWITCH TUNING DIAL DRIVER COIL

14 Me

14.250 Me

L-3

7 Me

7.250 Me

L-4

3.5 Me

3.750 Me

L-5

5.16 FINAL AMPLIFIER TUNING CHECKS:
The proper crystal should be inserted into the NCX-5 high frequency oscillator for operation at BAND switch settings of 28, 29, and 29.5 Me. If these crystals are not available, final amplifier tuning checks in these BAND switch settings cannot be made.
Set the BAND switch to 28.0 Me. Set the main tuning dial to 28.250 Me. Tum the FUNC’riON switch to TUNE and peak the EXCITER TUNE for maximum meter reading. Rotate the PA TUNE control and observe whether a dip appears in the reading. Advance the PA LOAD control in a clockwise direction and retune the PA TUNE control to maintain the output circuit in the dip. Continue this procedure until the minimum reading in the dip corresponds to 300 rna on the meter. Power output at this setting should exceed 100 watts and proper neutralization should be observed.

18

Repeat this check with BAND switch and main tuning capacitor set for the following frequencies. If necessary, mixer and driver coils may be slightly readjusted to maintain proper tracking across the band providing sufficient drive and proper final amplifier operation is achieved.

BANDSWITCH
29 Me 29.5 Me 21.0 Me 21.0 Me 14.0 Me 14.0 Me
7.0Mc 7.0Mc 3.5Mc 3.5Mc

MAIN TUNING DIAL
29.25 Me 29.75 Me 21.00 Me 21.50 Me 14.00 Me 14.50 Me
7.00 Me 7.30 Me 3.50 Me 4.00Mc

5.17 LOCAL OSCILLATOR CRYSTAL ADJUSTMENT:
Set the BAND switch to 7.0 Me. Turn the crystal calibrator ON. Tune to any crystal calibrator signal. The dial should read an exact 100 Kc point. Two beat notes may be noted. Adjust the 11 Me crystal trimmer (C-9) and the main tuning dial to set both beat notes to zero.
Repeat this procedure on the 14.0 Me band and set the 18 Me crystal trimmer (C-10).
Repeat this procedure on the 21.0 Me band and set the 25 Me crystal trimmer (C-11) .
The accessory crystal trimmers may also be set by this procedure according to the following chart:

BANDSWITCH
28.0 Me 28.0 Me 28.0 Me

10METER SEGMENT
SWITCH
28.0 Me 29.0Mc 29.5 Me

CRYSTAL FRE-
QUENCY
24.5 Me 25.5 Me 26 Me

CRYSTAL TRIMMER
C-14 C-13 C-12

5.18 PARASITIC CHECK:
Press the MOX-OFF switch to MOX. Adjust CARRIER BALANCE control for minimum current. Tune PA TUNE, PA LOAD, and EXCITER controls through their ranges. Look for unwanted spurious peaks on the meter. There should be none. Repeat this test on all bands.

5.19 CARRIER SUPPRESSION, SIDEBAND SUPPRESSION, MODULATION, AND ALC CHECKS:
Connect the audio generator to the microphone jack and supply 10 mv of audio signal to the NCX-5. Rotate the FUNCTION switch to the SSB setting. Connect the high-frequency oscilloscope to the antenna line which is connected to the dummy load. Rotate the CARRIER BALANCE control full cw or full ccw. Tune the final amplifier for maximum out-

put at 300 rna input as described in the previous sections. A level well in excess of 100 volts peak-topeak should be noted on the oscilloscope. Now slowly rotate the CARRIER BALANCE control towards mid-point. The oscilloscope level should fall and the meter reading should fall. Set the CARRIER BALANCE control for minimum indication on the oscilloscope which should correspond to minimum indication on the meter. Adjust the BIAS control for 60 rna on the meter. The level remaining on the oscilloscope should not exceed 0.5 volt peak-to-peak, thus insuring carrier suppression better than 50 db. If necessary, carefully adjust the balanced modulator plate trimmer (C-7) for minimum indication while rocking the CARRIER BALANCE control through minimum until the required 0.5 volt level is obtained.
Now rotate the MIC GAIN control slowly in a clockwise direction. A signal should again appear on the oscilloscope. The MIC GAIN should be advanced until the cathode current meter reads 250 rna. Output at the scope should be 120-180 volts. The wave form at this point should appear as indicated in figure 6A. It is necessary to note the level of ripple on the wave form to total wave form level. The ripple should not exceed 1/50 of the total wave form. This indicates that the unwanted sideband suppression with a 1000 cycle tone is in excess of 34 db.-the limit of this measuring technique.
It is important to note the difference between carrier balance and unwanted sideband suppression in the previous measurement. If the CARRIER BALANCE control is rotated slightly, the wave form of figure 6A will be altered to the wave form of figure 6B. If this wave form is present while attempting to make the sideband suppression measurement, the CARRIER BALANCE control should be slightly adjusted to compensate and return the picture to that of figure 6A.
Now further advance the MIC GAIN until the meter just reaches 300 rna as set by our previous tune-up procedure. Note the oscilloscope level. Slowly advance the CARRIER BALANCE control either cw or ccw from the balance setting. As this occurs, the wave form will begin to develop large cusps and peaks which will tend to exceed the noted oscilloscope level. Slowly reduce the MIC GAIN to keep the peaks at the predetermined level by carefully adjusting both the MIC GAIN and the CARRIER BALANCE control. It should be possible to obtain a picture as illustrated in figure 6C. It is important that the peaks of this figure be at exactly the level determined with the balanced carrier at 300 rna of cathode current. This is equivalent to a two-tone test and is useful in indicating distortion in the transmitter channel and performance of the modulating circuits. The wave form which is observed should have a clean sharp cusp and should have a sine wave envelope. There should be no flattening of the peaks and no broadening of the cusps. Typical incorrect wave forms are indicated in figure 6D ·& 6E.

19

Advance the MIC GAIN control to maximum ·and readjust the CARRIER BALANCE control for sharp cusps. The final amplifier should now be overdriven and ALC voltage should result. The oscilloscope wave form should remain as shown in figure 6C. Check the ALC output at the junction of D-9, R-34, R-35, and C-48. There should be approximately -5 volts at this point. Check the ALC voltage at the junction of D-8, D-9, and C-50. The voltage at this point should be 1/2 of the previous reading. This checks the action of the internal ALC circuit.
The rear ALC jack may now be checked by applying -10 to -15 volts at the ALC input jack. The oscilloscope display amplitude should decrease, indicating external control.
Press the MOX-OFF switch to OFF and set the VOX-PTT switch to PTT.
If all of the tests are met satisfactorily, we can assume that the transmitter is working properly,’ although it is of some value to check the dynamic operation of the transmitter on the microphone. To do this, return the MIC GAIN to zero and balance the carrier with the CARRIER BALANCE control. Now remove the audio generator from the microphone jack and replace it with the test microphone. Press the push-to-talk button and speak normally into the microphone. Slowly advance the MIC GAIN control until the peaks of the resulting signal reach the amplitude used for the previous two-tone type of test. At this point, the meter will be fluctuating rapidly with the speech content. The meter should generally average around 125 rna of current and the output wave form should appear as illustrated in figure 6F.
5.20 TRANSMIT-RECEIVE FREQUENCY CHECK:
Set the BAND switch to 3.5 Me and the dial to 3.700 Me. Tune the final amplifier using the TUNE function. Return the FUNCTION switch to SSB and press the MOX-OFF switch to MOX. Return the MIC GAIN control to the full ccw position. Now rotate the CARRIER BALANCE control until 300 rna is indicated on the meter and output appears on the oscilloscope. Press the MOX-O FF switch OFF. Tune an accessory receiver to 9.72 Me and couple lightly to the NCX-5 VFO. A beat note should be noted. Press the MOX-OFF switch to MOX. The

beat note indicated by the accessory receiver should not change more than 50 cycles. Press the MOX-OFF switch OFF.
5.21 LSB-USB SWITCHING CHECK:
Proper sideband switching may be easily checked with the D .C. voltmeter according to the chart below.
5.22 SWITCHING TESTS:
The transmitter portion of the NCX-5 is presently connected to a dummy load with an oscilloscope. Tune the NCX-5 to resonance for maximum power output. Balance the carrier. With these conditions established, now check the entire switching sequence in the following manner:
1. Place the FUNCTION switch in SSB and the PTT-VOX switch in the PTT position, and MOX-OFF switch OFF. Press the pushto-talk button and speak into the microphone. A standard single sideband output should appear on the oscilloscope. Release the pushto-talk button. The NCX-5 should revert to receive.
2. Press the MOX-OFF switch to MOX and speak into the microphone. SSB output should result. Return the MOX-OFF switch OFF and the NCX-5 should revert to receive.
3. Place the VOX-PTT switch in the VOX position. While speaking into the microphone, slowly advance the VOX GAIN control until the relay trips the unit into transmit. Stop speaking and the transceiver should return to receive.
4. While speaking into the microphone to cause the NCX-5 to transmit, adjust the DELAY control full ccw, stop speaking, and the NCX-5 should go back to receive in approximately 1/ 10 of a second.
5. Tum the DELAY control full cw and speak into the microphone. The NCX-5 should switch to transmit; stop speaking and the NCX-5 should return to receive in one second. In each case, a standard singlesideband signal should be observed on the

TEST POINT

LSB

USB

BAND

3.5 7.0 14.0 21.0 28.0

3.5 7.0 14.0 21.0 28.0

1

+ 150 -35 -35 -35 +150

-35 + 150 +150 + 150 -35

2

-80 0 0 0* -80

0 – 80 – 80 -80 0

3

0 -80 -80 -80 0

-80

0*

0*

0* -80

*SHOULD BE -40 WITH AM RECEIVE CONDITION ONLY

Test Point Location: 1. }7, Pin 3 (Calibrator Socket)

2. Junction of R-65 and C-153

3. Junction of R-61 and C-64

20

oscilloscope while speaking into the microphone.
6. Set the FUNCTION switch to AM and repeat the above tests for PTT, VOX, and MOX operation.
7. While speaking into the microphone, adjust the CARRIER BALANCE control from the balance point and observe the introduction of carrier into the sideband signal on the oscilloscope.
8. Place the FUNCTION switch in the CW position. Advance the VOX GAIN control full cw (maximum sensitivity) . Speaking into the microphone in this .condition should not result in transmit-receive switching.
9. Set the VOX-PTT switch to PTT and press the PTT button. The NCX-5 should not switch into transmit.
10. Press the MOX-OFF switch to MOX. The NCX-5 should switch to transmit. Return the MOX-OFF switch to OFF.
11. Insert a key into the key jack. A tap of the key should place the NCX-5 into a transmit condition. Upon release of the key, the unit should revert to receive in 1/10 of a second to one second, depending on the setting of the VOX DELAY control.
12. Hold the key closed, speak into the microphone and advance the MIC GAIN control. There should be no evidence of modulation on the oscilloscope.
13. Set the transmitting key for a long series of dots. Adjust th~ CARRIER BALANCE control for transmitter output just below full power. Observe the series of keying pulses on the high-frequency oscilloscope. A proper keying pulse should appear as in figure 6G. Figure 6H and 6I indicate improper keying sequences.
14. Set the FUNCTION switch to TUNE. Observe that full power output is attained on the oscilloscope. Adjust the CARRIER BALANCE control. There should be no change in the output signal.
15. Speak into the microphone and advance the MIC GAIN control. There should be no evidence of modulation on the oscilloscope.
16. Return the FUNCTION switch to SSB.

5.23 TRANSCEIVE VERNIER:
Set the NCX-5 to 3.700 Me. Tune the accessory receiver to 9.72 Me and lightly couple to the NCX-5 VFO. Observe that the beat note may be varied more than + 5 Kc with the TRANSCEIVE VERNIER. Press the MOX-OFF switch to MOX. Observe that the beat note cannot be varied with the TRANSCEIVE VERNIER and that it corresponds to the beat note previously heard with the MOX-OFF switch OFF and the TRANSCEIVE VERNIER at mid-range. Turn the TRANSCEIVE VERNIER OFF and observe that the beat note does not change. Return the NCX-5 to receive.
Disconnect all test equipment.
-CAUTION-
IN THE FOLLOWING SERIES OF TESTS, THERE IS NO LOAD ON THE TRANSMITTER OUTPUT. IF THE UNIT SHOULD GO INTO TRANSMIT UNDER THIS CONDITION, SERIOUS DAMAGE CAN BE DONE TO THE FINAL OUTPUT STAGE. ALSO DURING THIS SERIES OF TESTS, A SIGNAL GENERATOR WILL BE CONNECTED TO THE ANTENNA TERMINALS. SERIOUS DAMAGE CAN BE DONE TO THIS SIGNAL GENERATOR IF THE UNIT IS ACCIDENTALLY PLACED INTO TRANSMIT.
5.24 ANTI-VOX CHECK:
Connect the signal generator to the antenna terminals through a suitable dummy load to match the 50 ohm input impedance. Set the signal generator for 4.0 Me, the BAND switch to 3.5 Me, and the main tuning dial to 4.0 Me until a beat note is obtained at a frequency of approximately 1000 cycles. Connect the power output meter to the audio output terminals by use of the phone jack. Set the AUDIO GAIN control for approximately ~ watt. Measure the D.C. voltage at the junction of D3, R103, R107, and C157.
A voltage of more than + 10 volts should be in-
dicated at this test point.
5.25 VFO JACK:
Connect 100 ohms from the VFO jack to ground. The beat note should disappear, indicating that the VFO is not functioning. Feed an external signal into the VFO jack between 9.52 and 10.02 Me. It should be possible to retune the beat note with the external signal. Remove the external signal and the 100 ohm resistor. The original beat note should reappear.

21

TOP VIEW
FIGURE 4
BOTTOM VIEW
FIGURE 5 S3A R4
RB
S7
22

A C (CORRECT)

NCX-5 WAVE FORMS
FIGURE 6
IPPLE

0 (CLIPPED)

E (POOR CUSPS)

F G
I H
23

SECTION 6
PARTS LIST

Jl J2,J3 J4 ]5 ]6 ]7 ]8
]9

SOCKETS AND JACKS

Antenna

A51479

Ext. VFO In, Ext. ALC In A51084

MIC

A50793-2

Key

A50793-1

Phones

A50793-3

Octal

B27674-1

Jones Male

A50791

Jones Female

A50828

Relay Terminal Strip

A51563

Relay Socket

A50954

Navar

A50802

9 Pin

B27668-1

7 Pin

B27669-3

Transistor

A50981

X tal

A50799

Panel Lamp, Counter

A51607

Panel Lamp

B50829-2

POTENTIOMETERS AND CONTROLS

Rl R2 R3 R4,R8
R5 R6
R7 R9

BIAS

B50541-1

S-METER

B50541-3

MIC GAIN

B50541-9

RF GAIN- AUDIO GAIN B51550

– CAL SWITCH

VOX GAIN

B50541-2

TRANSCEIVE VERNIER B50986-2

and SWITCH

VOX DELAY

B50541-4

CARRIER BALANCE

B50541-1

RESISTORS

R38

1.5 K 2o/o Y2 W

R39

3.2 ohm 3% 2W WW

R52, R109
R108, R114
RllO Rlll R113

10.0 K Film
2.2 K Film
470 ohm Film 33.0 K Film 470 K Film

RS 20BF152G
B51743610
A51559-3
A51559-2
A51559-1 A51559-4 A51559-5

C5,C6, C17, C18
C7 C8,C9,
ClO, Cll, C12, C13, C14

TRIMMERS Ceramicon 5 – 25 NPO
Mica, Balance Mica Assembly

B19783-2
A50137 B50993-6

TRIMMERS (Cont)

C15

Air, Neutralization

B50364

C16

Ceramicon 1.5 – 7 NPO B19783-5

CAPACITORS

Cl

Gang: VFO- (Main)

C51507

Tuning

C2

Gang: EXCITER TUNE C50790-2

C3

Gang: PA TUNE

C50789-2

C4

Gang: PA LOAD

C50788

C20

Electrolytic

C19458-6

C34

Ceramic 82 pF 5% NPO A50849-4

spec. rating

C35

Ceramic 51 pF 5o/o NPO A50849-2

spec. rating

C36, C40 Ceramic 75 pF spec. rating A50849-3

C41, C47 Ceramic 500 pF spec. rating A50849-5

C70

Ceramic 5pF N220

CC 20 RH

050 K

C165

Ceramic 10 pF N750

CC 20 UJ

100 K

C166

Ceramic 47 pF N750

CC 20 UJ

470 K

C181

Ceramic 120 pF OTC Spe- A50113-2

cial

T1 T2, T3 T4, T5,
T6 T7

TRANSFORMERS

Balanced Modulator Output B50764

Bandpass 3.5 to 4.0 Me B51513

IF 6.02 Me

B50766

Audio

B19435-3

COILS AND CHOKES

Ll

10 Meter DriYer

L2

15 Meter DriYer

L3

20 Meter Dri·er

L4

40 :Meter DriYer

L5

80 Meter Driver

L6

10 Meter Mixer

L7

15 Meter Mixer

L8

20 Meter Mixer

L9 and 40 Meter Mixer

L29

LlO

80 Meter Mixer

Lll

Final Tank

L12

Choke, Special

L13, L16, Choke, 220 [-lh

L17,

Ll9,

L20,

L21,

L23

L14

p. a. Choke

L15

Choke, Final Grid 100 [-lh

L18

Choke 10 [-lh

B51517 B51515 B50759 B50757 B50755 B51516 B51 5 14 B50760 B5 1581
B50756 B51518 B51554 A50206-1
R154 NCL NCL R33 C50527-8

24

COILS AND CHOKES (Cont)

L22

Choke 4.7 !lh

L24, L25 Choke, Parasitic

L26

Choke, Antenna

L27

Coil VFO

L28

Choke VFO 3.3 !lh

C50523-5 B51545 C50523-3 B51520
R1550-19

SWITCHES

S1-A
S1-BC
S1-DE S1-FG S1-HI S1 S1
S2 S3-AB S3-CDE S4 S5 S6 S7 S8

Bandswitch, SB Interlock, VFO
Bandswitch, SB Interlock, Carrier Osc.
Bandswitch, Mixer Output Bandswitch, Driver Output PA Bandswitch Detent Shaft Sideband Selector Function Switch, Front Function Switch, Rear 10 Meter Switch Rocker MOX-OFF Rocker VOX-PTT Part of Gain Controls Part of Transcei’e Vernier

A51524
A51522
A51521 A51525 A51523 B51558 A50854 B51526 B51527 B51541 B51549 B51548-2 B51548-1 B51550 B50986-2

KNOBS
Function, Sideband Selector, Bandswitch
PA Load, Exciter ‘Tune, Transceive Vernier
PA Tune Main Tuning Audio Gain Lever, RF Gain, 10 Meter Switch

NPS-7K2LA
NPS-7F2LA NPS-7::!LC NPS-17D2LA NPS-7:3LC A51399

SHAFTS, COUPLINGS, DRIVE TRAIN

Shaft, Function Switch Shaft, PA Tune Shaft, Exciter Tune Shaft, PA Load

A51551 A51561-1 A50818-2 A50818-3

SHAFTS, COUPLINGS, DRIVE TRAIN (Cont)

Coup-Link Bushing, Panel Palnut 3/ 8-32 Coupling, Function Switch Coupling, Bandswitch Drive Train, VFO, With
Counter, Without Gang

B25000 A50840-0 B19322-8 J654-2 A12611 A51681

COVERS
Cover, PA Cover, VFO Top Cover, VFO Bottom Cover, Second Mixer

C50815 B51560 B51587 C51505

MISCELLANEOUS PARTS

Front Panel Bushing, Hanger Nuts for Above Lockwasher for Above Hanger Bracket Hanger Screws Hanger Pins Cabinet Foot, Rubber, Extension Foot, Rubber Cabinet Cover

E51502-5 A50817 A50117-7 5j 8 KCE B50836 B50835 A50860-1 E51580-2 A50850 A50851
D51579-3

MISCELLANEOUS ELECTRICAL

M

Meter

C50833

F-1

Filter, Xtal

A51557

D-2

Diode, Varactor

A51307-9

X1

Xtal, 6.0200 Me

A51546-1

X2

Xtal 6.0234 Me

A51546-2

X3

Xtal 11.000 Me

A51555-1

X4

Xtal 18.000 Me

A51555-2

X5

Xtal 25.000 Me

A51555-4

X6

Xtal 26.000 Me

A51555-6

X7

Xtal 25.500 Me

A51555-5

X8

Xtal 24.5 Me

A51555-3

Rel

Relay 6PDT 8000 ohms A50798

25

SECTION 7
VOLTAGE AND RESISTANCE MEASUREMENTS

THE FOLLOWING DC VOLTAGE MEASUREMENTS ARE TAKEN WITH A VTVM WITH AN INPUT RESISTANCE GREATER THAN 10 MEGOHMS. RECEIVE VOLTAGES ARE TAKEN AT MAXIMUM RF GAIN WITH NO SIGNAL INPUT. TRANSMIT VOLTAGES ARE TAKEN WITH CARRIER BALANCE TUNED FOR MINIMUM INDICATION AND FUNCTION SWITCH IN THE SSB POSITION.

Tube Type

Function

Pin

1

2

3

4

V-1 6GJ5

FINAL AMPLIFIER

5

6

7

8

9

1

2

3

4

V-2 6GJ5

FINAL AMPLIFIER

5

6

7

8

9

1

2

FIRST

3

V-3 12BE6 TRANSMIT

4

MIXER

5

6

7

1

2

LOCAL

3

OSCILLATOR

4

V-4 6KE8 AND SECOND 5

TRANSMIT

6

MIXER

7

8

9

1

2

3

4

V-5 6GK6

DRIVER

5

6

7

8

9

1

2

SPEECH

3

AMPLIFIER

4

V-6 12AT7

AND

5

S-METER

6

AMPLIFIER

7

8

9

*AC OR DC DEPENDING ON SUPPLY

Resistance
10 k 20 k 3.2 n –
–
20 k 10 k 0 0
10 k 20 k
3.2 fl
–
20 k 10 k
0 0
100 k 0 0
–
–
30 k 100 k
10 k 200 k 100 k
0
–
15 k 470 fl
0 47 k
1so n 200 k
0 INF. 10 k 10 k
0
20 k 30 n 1 k
0 0 35 k 56 k 0
–

Voltage

Receive

Transmit

0

+250

-45 to -65 V ADJUSTABLE WITH BIAS CONTROL

0

.3 v

12.6*

12.6

6.3*

6.3*

-45 to -65 V ADJUSTABLE WITH BIAS CONTROL

0

+250

0

0

0

0

10 k

270

-45 to -65 V ADJUSTABLE WITH BIAS CONTROL

0

0

6.3*

6.3 *

0

0

-45 to -65 V ADJUSTABLE WITH BIAS CONTROL

0

270

0

0

0

0

-40 0 0 12.6*
240 240 -40

0 0 0 12.6* 270 30 0

150 -40 270
0 6.3* 270 0 0 -1

150 0
170 0 6.3*
260 2 0
-1

0 -40
0 6.3 12.6 0 300 250 0

8 0 0 6.3 12.6 0 300 270 0

75 0 1 0 0 250
.2 3 6.3*

85 0 1 0 0 0 6 0 6.3*

26

VOLTAGE AND RESISTANCE MEASUREMENTS (Cont)

Tube Type

Function

Pin

1

2

3

4

V-7

12AU7

CARRIER OSCILLATOR

5

6

7

8

9

Resistance
20 k 300 k
0
–
0 20 k 300 k 0
–

Receive
100 0 LSB, -60 USB
0 12.6 0 100 0 USB, -60 LSB 0 6.3

Voltage

1

2

MICROPHONE 3 PREAMPLIFIER 4

V-8 6GH8

AND

·5

RELAY

6

CONTROL

7

8

9

20 k 1 meg 600 k –
100 k 0 0 1.5 meg

150 -1 35
6.3 12.6 100 0 0 0

1

2

3

V-9

12AU7

vox
AMPLIFIER

4 5

6

7

8

9

100 k 800 k
1.5 k 0 100 k 10 meg 0
–

70 0 3 0 12.6 35 -.7 0 6.3

V-10 7360

1

2

3

4

BALANCED MODULATOR

5

6

7

8

9

2.5 k 150 k 500 k
0
–
15 k 15 k 50 k 50 k

0 0 -40 0 6.3* 250 250 25 25

V-11 6BZ6

1 2 3 1st RF STAGE 4 5 6 7

1 meg 220 fl –
10 k 80 k
0

0 +1
6.3 12.6 300 150
0

1 2 3 V-12 12BE6 2nd RF STAGE 4 5 6 7

470 k
0 0
–
15 k
82 k 270 fl

0 0 0 12.6* 270 130 2.7

1

2

1st

3

V-13 12BE6

RECEIVER

4

MIXER

5

6

7

150 k 0 0
10 k 56 k 10 fl

-.5 0 0 12.6* 250 200 0

AC OR DC DEPENDING ON SUPPLY +20 TO +30 VOLTS DEPENDING ON CARRIER BALANCE 0 ON TUNE FUNCTION. +20 TO +30 DEPENDING ON CARRIER BALANCE

Transmit
100 0 USB, -60 LSB
0 12.6 0 100 0 USB, -60 LSB 0
6.3
300 -1 35
6.3 12.6 -.9 0 0 -40
80 0 3 0 12.6 40 -.7 0 6.3
4 200
0 0 6.3* 250 250 25 25
0 0 6.3 12.6 300 0 0
0 0 0 12.6 250 0 0
-40 0 0
12.6* 250
0 0

27

VOLTAGE AND RESISTANCE MEASUREMENTS (Cont)

Tube Type

Function

Pin

Resistance

1

2

2nd

3

V-14 12BE6

RECEIVER

4

MIXER

5

6

7

120 k 0 0
10 k 56 k 120 k

Receive
0 0 0 12.6* 250 25 0

Voltage

1 2 3 V-15 12BA6 1st IF STAGE 4 5 6 7

1 2 3 V-16 12BA6 2nd IF STAGE 4 5 6 7

1 2 3 V-17 12BA6 3rd IF STAGE 4 5 6 7

1

PRODUCT

2

DETECTOR

3

V-18 12AX7

AND 1st

4

AUDIO

5

AMPLIFIER

6

7

1

2

3

V-19 6AQ5

AUDIO AMPLIFIER

4

5

6

7

V-20 OA2

1

2

3

VR TUBE

4

5

6

7

*AC OR DC DEPENDING ON SUPPLY

40 k 0 0
–
10 k 40 k
120 n
180 k 0 0 30 k 15 k
120 n
150 k 0 0
–
100 k 150 k
150 n
100 k 40 k
Sk
–
0 300 k
10 meg
800 k
470 n
0 10 k 10 k 800 k
8k 0 INF. 0 8k INF. 0

0 0 0 12.6 240 150 2
.2 0 0 12.6 240 65 1
0 0 0 12.6 240 110 2
200 0 2.8
12.6 0 100 -.6
0 15
0 6.3* 300 250 0
150 0 0 0
150 0 0

Transmit
-40 0 0
12.6 250
0 -40
0 0 0 12.6 260 150 2
0 0 0 12.6 260 65 1
0 0 0 12.6 0 0 0
260 -45
0 12.6
0 250 -23
0 0 0 6.3 300 250 0
150 0 0 0
150 0 0

28

CAPACITORSI I N pF. I F POINT(.) PRECEDES DIG1TS:fiF. 20UUNLESS OTHERWISE SPECIFIED.

RESIST0RS:IN OHMS: K=KILOHMS. M=MEGOHMS. POUUNLESS OTHERWISE SPECIFIED.

SWITCHES: ALL SHOWN FULL C C W , F R O ~THIS POSITION

CLOCKWISE ROTATION WILL RESULT AS FOLLOWS: SI-BANDSWITCH 28-21-14-7-3.5 Mc.

S2SlMBAND LSB-USE.

s3-FUNCTIONOFF-SSB-AM-CW-TUNE

S M METER 29.5-29.0-28.5-28.0

f SYMBOLS:

VARlA8LE COMPONENT

/ ADJUSTABLE COMPONENT

L G R O U N D . CHASSIS

;,RSS3K3 10%

0 CAL SOCKET.J7–D
NCTION S W . S 3 4 RECEIVER B I A S 4

OC FROM FINAL

C FROM AGC D E T . 4

–TO FINAL GRID COUPLING V 3 AND BIAS CONTROL-

r RECEIVE 3 BlAS TO VFO-

BIAS FROM St-C-<

FROM MlC KE

TO PTT DIODE 0 4

-RF GAl BIAS CONTROL-

S3:OFF-SSB-AM-

+TO ANTENNA JACK +TO

RELAY

TO B A L MOD. VIO

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