JRC NRD-525 General Coverage Receiver Instruction Manual

JRC NRD-525 General Coverage Receiver Instruction Manual

Thank you for purchasing the NRD-525 General Coverage
Receiver.

The NRD-525 is a high · quality receiver with the latest digital circuits and semiconductors developed from many years of JRC’s experiences and achievements in the field of radio communication. Please read through this manual before use.

The product you have purchased is produced under strict quality control. Should you find any trouble or damage, please contact the nearest JRC branch or dealer as soon as possible.

ACCESSORIES
The NRD-525 has the following accessories. Check your accessories against the following list:

• Instruction manual ……… 1
• M type coaxial plug ……… 1
• Pin plug ……… 1
• Phone plug ……… 1
• Record plug ……… 1
• 1-A fuse ……… 1
• DC power cord (6ZCJD00127) ……… 1
• AC power cord ……… 1

PRECAUTIONS

1. Even when the power for the Receiver is switched off, a small amount of current flows for backup of the clock. If you are going to leave the Receiver unused for a long time, remove the AC or DC power cable on the rear panel. (Then, the clock will not be backed up.) Take special care when a battery is used as the power source.
2. Read the markings on the corrugated cardboard package and confirm the voltage of the AC power source which you can use.
3. If you are going to use DC mains as the power source for the Receiver, use the correct DC power cable. If you are going to use any other cable, be sure to fit an in-line 3A fuse.
4. Never connect an AC power source to the timer output terminal. It is very dangerous!

Nomenclature
(While reading the text, you may refer to this page for identification of parts from time to time.)

Front panel

1. POWER/TIMER ON·OFF switch
2. AF GAIN control
3. TUNING control (This control also works as RIT control when characters “Rlr’ are on.)
4. UP switch
5. LOCK switch
6. DOWN switch
7. RF GAIN control
8. BFO control
9. TONE control
10. NOTCH control (It also works as P LEVEL (pause level) control during scan or sweep reception.)
11.  SQUELCH control
12. PBS (pass band shift) (It also works as the SPEED control during scan or sweep reception.)
13. PHONES jack
14. RECORD jack
15. NB LEVEL (noise blanker level) control
16. RIT switch
17. DIMMER switch
18. MONI (monitor) switch
19. CLOCK/TIMER switch
20. SCAN switch
21. SWEEP switch
22. RUN switch
23. ATT (attenuator) switch
24. AGC control
25. Vacuum Fluorescent Display (VFD)
26. BANDWIDTH switch
27. MODE switch
28. Numerical keys
29. FREQ (frequency) switch
30. CHANNEL switch
31. CLR (clear) switch
32. MHz switch
33. ENT / kHz switch
34. MEMO (memory) switch

In the above figure, Un , 50), and GD are positioned supposing that the options are mounted.

Rear panel

1. MF /HF ANT LoZ Clown impedance) connector
2. ANT switch
3. MF/HF ANT Hi-Z (high impedance) terminal, GND (grounding) terminal
4. LINE OUT (line output) jack
5. EXT SP (external speaker) jack
6. SIDE TONE jack
7. MUTE jack
8. DC OUT (DC output) jack
9. TIMER OUT (timer output) terminal
10. PRINTER connector
11. Jack for RTTY indicator
12. DC power connector
13. Connector for RS·232C
14. AC power connector
15. AC fuse, voltage selector
16. VHF ANT connector
17. UHF ANT connector

1. FEATURES

1. Wide receiving frequency range The standard receiving frequency range is from 90 kHz to
   34MHz. If the optional VHF /UHF Converter is installed, the receiving frequency ranges of 30-60, 114-174, and 423-456 MHz can be used. This extends the range of application of the receiver.

2. Wide dynamic range
   Use of a grounded gate push-pull FET mixer and electronic tuning system secures a wide dynamic range with the emphasis put on multiple-signal characteristics.

3. Electronic tuning system
   The automatic tuning method incorporated in the widely accepted JRC’s professional purpose receivers is employed.
   (The double tuned circuit with capacitor diodes, controlled by a microcomputer.) This gives improved front end selectivity, and better matching to the antenna.

4. Large memory capable of storing 200 channels
   The CMOS-RAM backed up by a lithium battery can store a maximum of 200 channels, each channel containing data on the frequency, mode, bandwidth, AGC, and ATT.

5. Scan sweep reception
   If a start channel (frequency for sweep) and end channel (frequency for sweep) are set, scan reception (sweep reception) can be carried out. Sweep speed and stop level are adjustable.

6. Frequency stability to high quality receiver standard The± 3 PPM standard frequency oscillator assures high frequency stability in each of the MF, HF, VHF, and UHF
   bands.

7. Teletype reception
   Use of the optional RTTY demodulator allows teletype reception. Any Centronics compatible printer can be used.

8. Clock/ timer
   The two built-in clocks can be used as Local time and UTC (GMT). They can be also used as a timer to control a tape recorder, etc.

9. Direct access tuning
   In addition to the flywheel tuning control, the frequency can quickly be selected by numerical keys.

10. Compatibility with personal computer
    The optional RS-232C interface allows control from a personal computer. For instance, the frequency, mode, bandwidth, time, and other data may be entered into the program. Thus, the Receiver works as a programmable automatic receiver.

11. Adoption of latest manufacturing techniques
    The NRD-525 employs as many surface mounted parts as possible, including resistors, capacitors, transistors, and diodes. Thus, automated production, consistent quality, and cost cutdown have been achieved. Employment of plug-in type PCB modules has improved reliability and serviceability.

12. All-in-one construction
    All the optional units such as the RS-232C interface, RTTY  and VHF /UHF converter can be housed in the receiver cabinet.

13. Built-in loudspeaker
    No externally mounted units are necessary for reception because the Receiver has a built-in loudspeaker.

14. Dual power supply system
    Either 100/ 120/ 220/ 240 V AC or 13.8 V DC can be used as the power source. Therefore, the Receiver can be used both indoors and outdoors.

2. RATINGS

1. Receiving frequency range 0.09·34MHz

2. Receiving mode
   34-60MHz(See NOTE 1.)
   114-174MHz(See NOTE 1.)
   423-456MHz(See NOTE 1.)
   RTTY, CW, SSB(USB, LSB)
   AM, FM, FAX

3. Memory ·channel 200 channels

4. Receiving system · Double super heterodyne
   1st IF 70.45399· 70.453MHz
   2nd IF 455 kHz

5. Sensitivity
   S/N = l0dB, AF output= l00mW, bandwidth= INTER
   Modulation=400H2 , 30%(during AM measurement)
   NQL= 20dB(during FM measurement)
   Antenna impedance= 50

6. Selectivity

7. Image frequency rejection ratio 70 dB or more

8. Intermediate frequency rejection ratio 70 dB or more

9. Frequency stability ±3 PPM

10. Dynamic range 100 dB or more (with 500Hz IF selectivity)

11. PBS variation range ±1 kHz or more

12. Notch attenuation -30 dB or more

13. BFO variation range 455 kHz±2 kHz or more

14. RIT variation range ±5 kHz, maximum

15. Nominal Antenna impedance 0.09-34MHz 50O(Lo-Z terminal)
    600O(Hi-Z terminal)
    34-60MHz 50O(VHF terminal)
    (See NOTE 1.)
    114-174MHz 50O(VHF terminal)
    (See NOTE 1.)
    423-456MHz 50O(UHF terminal)
    (See NOTE 1.)

16. AF output Speaker output : 0.5 W or more (at 40 load and 10% distortion) Line output: 1 mm or more (at 6000 load and 10% distortion) Recording output : 1m W or more

17. Antenna input attenuation Approx. 20 dB for HF Approx. 10 dB for VHF/UHF (See NOTE 1.)

18. AGC characteristic Change of output is 10 dB or less when the antenna input changes by 3μV to 100 mV.

19. Power source 100/ 120/220/ 240 V AC ± 10%
    Max. 35 VA 12-16V DC (standard 13 .8 V) Max. 25 W

20. Auxiliary circuits Noise blanker. S meter, side tone input, mute input, transmission monitor, squelch. dimmer. tone control. clock, timer. IF notch filter , pass band shift

21. Dimensions 330(W) x 130(H) X 280(D)(excluding projected parts)

22. Weight Approx. 8.5 kg

NOTE 1 :With the optional V.UHF converter CMK-165.
NOTE 2 :If the optional If filter (e.g. CFL-231) is mounted, the bandwidth for 6d8 is 0.3 kHz.
NOTE 3: With the optional If filter CFL-233.

3. BEFORE USE

3.1 Mounting Place

For installation, avoid a place where the Receiver can be exposed to direct sun, hot air from an air conditioner, dust, vibration, or humidity so that you may use the Receiver for a long time with its performance fully maintained. Select a well ventilated place.

Ensure a sufficient clearance behind the Receiver so that it may not be closely put to the wall.

3.2 Mounting

To operate the set, such preparations must be made as erection of the antenna, grounding, and connection to the power source. Connect the components as shown in Fig. 3-1.

1. Erection of antenna
   The antenna should preferably be mounted outdoors to have the Receiver operate at it’s best performance. Use an HF antenna with a low impedance (e.g. the inverted L type preferably with the vertical portion height of 10 metre or more and the horizontal portion length of 10 to 20 metres, doublet type, or Yagi type. Connect one end of the coaxial cable (500 or 750) to the antenna, and the other end to the MF/ HF ANT Lo-Z connector on the rear panel. In doing so, do not forget to put the ANT switch to the Lo-Z position. If a high impedance antenna such as 4- to 6-m long vinyl coated wire is to be used, connect it to the MF HF Hi-Z terminal on the rear panel. In this case, the ANT switch must be put to the Hi -Z position.

2. Grounding
   Reception is possible without grounding. However, to prevent electric shock and damage to devices, connect a thick copper grounding wire to the GND terminal on the rear panel.

3. Connection to power source
   If you are going to use an AC power source, connect the correct AC power cable to the AC power connector on the rear panel. To operate the receiver from a DC, connect the DC power cable to the DC power connector on the rear panel. The AC power source voltages. which you can use are marked on the package. Ascertain that these values are identical to the voltages marked on the voltage selector on the rear panel. If any other voltage is to be used, select a voltage nearest to that you are going to use, from l00V, 120V, 220V, and 240V, and set the voltage selector at that value, provided that the difference between these voltages should be within± 10% of the voltage marked on the voltage selector.

4. Connection of speaker
   The Receiver has a built-in speaker, but an external speaker can be connected to it if necessary. Use of the JRC NVA-88 (option) is recommended.

5. Connection of headphone
   We recommend use of the JRC communications headphones ST-3 (option). If you are going to use headphones of any other type, select one with impedance of 4 to 160. A stereo record player headphone can be used as it is.

4. SWITCHES AND CONTROLS ON PANELS

4.1 Front Panel

1. POWER/TIMER ON-OFF switch
   If this switch is put to the POWER position, the power is switched on, and the NRD-525 begins to operate. If it is put to the TIMER position, the timer functions. If it is put to the OFF position, the Receiver does not operate. Please note that a small amount of current for internal clock circuit flows while the switch is in OFF position.

2. AF GAIN control
   Controls the AF (audio) output level. Turning it clockwise increases the volume of sound.

3. TUNING control
   Changes the receiving frequency in 10 Hz steps. Turning it clockwise increases the frequency. If the RIT switch is turned on, this control works as the RIT control.

4. UP switch
   If the FREQ switch (29) is turned on, you can increase the frequency in 1 kHz steps (5 kHz steps in the FM mode) with this switch. If the CHANNEL switch (30) is turned on, you can increase the channel number. Use this switch together with the DOWN switch (6). Because this switch is of auto repeat type, the frequency or channel number increases continuously while it is pressed. The DOWN switch also works in the similar manner.

5. LOCK switch
   If this switch is turned on, the (3). (4), (6), (16), (18) through (24), and(26) through (34) controls and switches are electrically disabled. This switch may be used if you want to avoid erroneous operation during reception.
   If the switch is turned on, the red LED at the center of the switch is lit to indicate the locking.

6. RF GAIN control
   This control is used to adjust the gain of the 1st and 2nd intermediate frequency amplifiers. If it is turned fully clockwise, the gain is maximum. As you turn it counter clockwise after turning it fully clockwise, the gain decreases gradually. At the same time the S meter begins to deflect. When the S meter indicates S9, the total gain of the 1st and 2nd IF amplifier is attenuated by about 40 dB. If the control is turned fully counter clockwise, the gain is attenuated further, and neither receiving signal nor noise can be heard. Then, the S meter will not move because it has reached the limit. If you are receiving a relatively strong signal, set this control at a value equivalent to or a little smaller than the reading of the S meter. Then, the noise between signals will reduce and you can hear easily. Ordinarily, this control is turned fully clockwise.

7. BFO control
   This control works only in the CW mode. It changes the tone of the AF (audio) output. Rotation of the control by one division of the scale can change the tone by about 500 Hz. The tone changes in the range of about+2.5 kHz when the control is turned from the neutral (central) position to the maximum. If this control is put to the neutral position when the Receiver is tuned to the carrier wave of the received signal, the beat of the AF (audio) output signal becomes zero, and beat note cannot be heard. Ordinarily, the BFO control is moved clockwise or counter clockwise from the neutral position. If the control is 🙂 moved by 1.5 division from the neutral position, the beat note of about 800 Hz can be heard. If CW is received with BFO control put to the neutral position, and the AF (audio) output is set at the zero beat with the 1 TUNING control (3), the frequency of CW currently received can be easily known from by reading the indication of the receiving frequency at that time.

8. TONE control
   This control is used to change the high frequency response of the AF (audio) output to adjust the sound quality. You can use this control to select any desired sound quality. Turning it clockwise increases the high frequency response. Ordinarily, it is put to the neutral position.

9. NOTCH control/P LEVEL (pause level) control
   If the received signal sustains heterodyne interference due to a continuous carrier or signal such as CW, this control may be turned clockwise from the OFF position to the ON position so as to minimize the heterodyne. If the control is put to the central position in the LSB or USB mode, the beat interference equivalent to about 1.5 kHz (AF output) can be eliminated. This control is used as P LEVEL (pause level) control for automatic pausing when scan or sweep is being executed with the RUN switch (22) depressed. As the control is turned counter clockwise, a stronger input signal is required for pausing. When pausing is accomplished, the red characters “PA USE” on the vacuum fluorescent display (25) are illuminated for warning.
   CAUTIONS
   1. The notch facility does not work when scan or sweep is being executed.
   2. IF the notch control is turned on, the received signal may be distorted. So, it should be turned off unless necessary.

10. SQUELCH control
    If the SQUELCH control is turned clockwise from the OFF position, the squelch is turned on. This control works in any mode. If the squelch is closed (if there is no AF output), red letters “SQL” on the vacuum fluorescent display (25) are illuminated for warning. As the control is turned clockwise, higher input level is required to open the squelch. If the squelch is opened, the “SQL” indication goes out. The SQUELCH control will not work when the AGC is turned off.

11. PBS (pass band shift) control / SPEED control
    This control varies the apparent intermedia ate frequency for the IF filter by about ± 1 kHz without changing the receiving frequency. This function allows elimination of the adjacent signal by means of the edge of the filter when the side band of the adjacent signal is overlapped on the receiving frequency. If this control is turned counter clockwise from the neutral position in the USB mode, interference from higher components of the voice signal can be eliminated. At this time, the high band portion of the received signal is also cut (high cut). In the LSB mode, the above relationships are reversed. This control works as the SPEED control during scan or sweep reception. The speed is maximum when the control is turned fully clockwise. The speed becomes lower as the control is turned counter clockwise.
    CAUTION
    Signal quality is adversely affected if the Receiver is operated with the PBS (pass band shift) control turned fully clockwise or counter clockwise. Put the control to the neutral position unless necessary.

12. PHONES jack
    Output jack for the headphone. Use headphones with an impedance of 4 to 16 n. Stereophonic headphones can be used without modification. When using headphones, the internal and external speaker are automatically disconnected.

13. RECORD jack
    Used to record what is received on a tape recorder. The output level is independent of the position of the AF GAIN control. The output impedance is 600 n.

14. NB LEVEL (noise blanker level) control Strong pulse noise similar to the ignition noise from an automobile can be eliminated if this control is turned clockwise. As this control is turned clockwise, the sensitivity of the noise blanker becomes higher, and noise with fairly low level can be eliminated. Take care not to turn it excessively lest the received signal should be distorted. If this control is pulled forward, wide pulse noise such as “woodpecker” noise can be eliminated. In this case, the sensitivity can be adjusted by turning the control. Unless necessary, leave this control turned fully counter clockwise.

15. RIT switch (receiver increment tuning)
    This switch works only when FREQ switch (29) or the CHANNEL switch (30) is pressed. If this switch is turned on, the characters “RIT” and the amount of change in receiving frequency is displayed on the vacuum fluorescent display (25). The TUNING control (3) also works as the RIT control. It can change the frequency by maximum ±5 kHz.
    When using RIT, the UP switch (4), DOWN switch (6),
    CLOCK/TIMER switch (19), SCAN switch (20), SWEEP switch (21), FREQ switch (21), CHANNEL switch (30), and numerical keys become inoperative.

16. DIMMER switch
    This switch is used to change the brightness of the vacuum fluorescent display and LEDs. Each time the switch is pressed, the brightness changes in four steps from total extinction to maximum brightness.

17. MONI (monitor) switch
    In case the Receiver is used in combination with a transmitter, this switch allows monitoring of transmission signal. If the switch is turned on, the characters “MON!” on the vacuum fluorescent display (25) are illuminated in red.

18. CLOCK/TIMER switch
    This switch is used to select either CLOCK 1, CLOCK 2,
    TIMER ON, or TIMER OFF. Each time this switch is pressed, CLOCK 1, CLOCK 2, TIMER ON, or TII\!ER OFF is selected in that order. If it is pressed further, CLOCK 1 is selected again.
    • CLOCK 1 : Time such as local time is set.
    • CLOCK 2 : Time such as UTC (Universal Coordinated Time) is set.
    • TIMER ON: Time at which power for NRD-525 is switched on by the timer.
    • Timer OFF : Time at which power for N RD-525 is switched off by the timer.
    If CLOCK 1, CLOCK 2, TIMER ON, or TIMER OFF is selected, the time is indicated on the vacuum fluorescent display (25). At this time, the time can be set if desired.
    To clear the setting of the CLOCK/ TIMER switch, press the SCAN switch (20), SWEEP switch (21), FREQ switch (29), or CHANNEL switch (30) according to what you want to do. CAUTION
    All times are shown using the 24 hour clock.

19. SCAN switch
    This switch is used to select SCAN ST ART or SCAN END.
    Each time the switch is pressed, SCAN ST ART and SCAN END are selected in turn.
    • SCAN START: Channel number at which scan starts by means of the SCAN function.
    • SCAN END : Channel number at which scan ends by means of the SCAN function.
    If SCAN START or SCAN END is selected, the channel and the frequency, mode, bandwidth, status of AGC, on-off status of A TT are indicated on the vacuum fluorescent display (25). At this time, reception can be done with use of the information stored in the selected channel number. Also, the channel number can be set. In this status, scan is not executed. To execute scan, the RUN switch (22) must be turned on. At this time, it does not make any change whether SCAN START or SCAN END have been selected.
    To clear the setting of the SCAN switch, press the CLOCK/ TIMER switch (19), SWEEP switch (21), FREQ switch (29), or CHANNEL switch (30) according to your requirement.

20. SWEEP switch
    This switch is used to select SWEEP ST ART or SWEEP END. Each time the switch is pressed, SWEEP ST ART and SWEEP END are selected in turn.
    • SWEEP START: Frequency at which sweep starts by means of the SWEEP function.
    • SWEEP END : Frequency at which sweep ends by means of the SWEEP function.
    If SWEEP START or SWEEP END is selected, the frequency is indicated on the vacuum fluorescent display (25). At this time, reception can be done on the selected frequency. Also, the frequency can be changed. In this status, sweep is not executed. To execute sweep, the RUN switch (22) must be turned on. At this time, it does not matter whether SWEEP ST ART or SWEEP END have been selected.
    To clear the setting of the sweep switch, press the CLOCK/ TIMER switch (19). SCAN switch (20), FREQ switch (29), or CHANNEL switch (30) according to your requirement.

21. RUN switch
    This switch is used to execute scan or sweep.
    If this switch is turned on when the SCAN switch (20) is pressed and SCAN ST ART or SCAN END is indicated, scan begins with the start channel number. If this switch is turned on when the SWEEP switch (2 1) is turned on and SWEEP START or SWEEP END is indicated, sweep begins with the start frequency. If the RUN switch is turned on, the characters “RUN” on the vacuum fluorescent display (25) are illuminated. If this switch is depressed again, SCAN or SWEEP stops.

22. A TT (attenuator) switch
    This switch is used to turn on and off the attenuator (approx. 20 dB in HF band) in the antenna input circuit.

23. AGC switch
    The AGC switch is used to turn off AGC, or to select time constant (slow or fast) of AGC. Each time the switch is pressed, the AGC indication on the vacuum fluorescent display (25) changes in the order shown below. Select SLOW, FAST, or OFF according to your requirement.

24. Ordinarily, they are selected in the following manner.
    • AGC SLOW : If AGC SLOW is selected when relatively strong signal is being received, noise between signals is suppressed. Thus, you can hear the signal easily. Generally, this position is used in the SSB mode.
    • AGC FAST: If AGC FAST is selected when you are receiving strong and weak signals in turn, AGC quickly responds to the weak signal sent after the strong signal: Thus, you can hear the signal easily because the start of each signal is not cut off. Ordinarily, this position is used in the CW or AM mode.
    • AGC OFF : In this position, the S meter does not read at all. This position is used to receive relatively weak signal.
    Because the voice signal is distorted if strong signal is received, turn the RF GAIN control (7) counter clockwise to eliminate distortion. In the FM mode, this switch becomes inoperative.

25. Vacuum fluorescent display
    A large vacuum fluorescent display is used to indicate the items illustrated below.25-1 frequency indicator: Indicates receiving frequency in 7 digits. If RIT is on, the amount of change of RIT is shown in three digits. At this time, time is not shown.
    25-2 channel indicator : Indicates the channel number in 3 digits.
    25-3 time indicator: Time for CLOCK 1, CLOCK 2 , TIMER ON, and TIMER OFF is shown in 4 digits. At this time, the frequency is not shown.
    MODE : Indicates mode. Either RTTY. CW, USB, LSB, AM, FM, or FAX is selected and illuminated.
    /BANDWIDTH/ : Indicates the bandwidth. Either NARR, INTER, WIDE, or AUX is selected and lit.
    /CLOCK/1 : Lit to indicate time for CLOCK 1.
    /CLOCK/ 2: Lit to indicate time for C::LOCK 2.
    /TIMER/ON : Lit to indicate time for TIMER ON.
    /TIMER/OFF : Lit to indicate time for TIMER OFF.
    /SCAN /START : Lit to indicate scan start channel.
    /END : Lit to indicate scan end channel.
    /SWEEP/START : Lit to indicate sweep start frequency.
    /SWEEP/ END : Lit to indicate sweep· end frequency.
    /RUN/ : Lit in yellow during scan or sweep is being executed.
    /AGC/: Indicates the status of AGC. Either OFF, FAST, or SLOW is selected and lit.
    S (S meter) : Indicates the intensity of received signal in terms of 1 through 9, and 9+10dB through 9+50dB.
    RIT : Lit in red during execution of RJT.
    MONI (monitor): Lit in red during operation of transmitting monitor.
    SQL (squelch) : Lit in red when squelch is closed.
    PAUSE : Lit in yellow when scan or sweep is paused by manipulation of the P LEVEL (pause level) control (10).
    REMOTE: Lit in yellow when NRD-525 is remotely controlled by the optional RS- 232C unit.
    MR (memory read) : Lit in red when memory channel is read out.
    DC : Lit in red when NRD-525 is operated from a DC power source.
    ATT: Lit in red when attenuator is turned on.
    PASS : Lit when the input RF filter is bypassed.

26. BANDWIDTH switch
    This switch is used to select the bandwidth (for the IF filter).
    Press the switch to move the indication of the bandwidth on the vacuum fluorescent display (25) to the right or left to select the desired bandwidth. In the FM mode, you canner select the bandwidth with this switch because the bandwidth is fixed at 12 kHz. Ordinarily, the bandwidth is selected in the following manner according to the mode.
    • NARR (0.5 kHz): For reception in RTTY, or CW mode (with the optional filter CFL-232 mounted)
    • INTER (3 kHz): For reception in the USB, LSB or FAX mode.
    •WIDE (6 kHz): For reception of AM
    • AUX (12 kHz) : For reception of AM (without optional filter) If the optional filter is not mounted for the narrow band, NARR cannot be selected. Also, an optional filter can be mounted for AUX. In this case, the bandwidth equivalent to that of the optional filter can be used.

27. MODE switch
    Used to select the mode (type of emission).
    To select the desired mode, press switch and move the mode indication on the vacuum fluorescent display (25) to the right or left.

28. Numerical keys
    These are used to set the receiving frequency , channel, and time. If they are manipulated improperly, beeping sound is given in the speaker as a warning.

29. FREQ (frequency) switch
    If this switch is turned on, the LED at the center of the switch is illuminated in green. Then, you can set the frequency with numerical keys (28).

30. CHANNEL switch
    If this switch is turned on, the LED at the center of the switch is illuminated in green. Then, you can set the channel with numerical keys (28).

31. CLR (clear) key
    If you have made a mistake during entry of the frequency, channel, or time data with ten keys (2 8). press this switch to clear the data just entered. Then data set previously will be recovered.

32. MHz switch
    Used to set the frequency in MHz with numerical keys (28).
    Pressing this switch completes the data entry.

33. ENT /kHz switch
    In case a frequency setting in kHz, channel selection or time setting, press this switch after manipulation of the Numerical keys (28). Pressing this switch completes the data entry.

34. MEMO (memory) switch
    Used to store data in the memory channel, or to make user definition.

4.2 Rear Panel

(35) MF /HF ANT Lo-Z (low impedance) connector Thai MF/HF antenna connector is used to connect a low impedance (50 n) antenna. To use the NRD-525 to its full performance, use an antenna with as good a performance as possible.

(36) ANT SW (switch)
Used for selection between low and high impedance of the MF/ HF antenna.

(37) MF/ HF ANT Hi-Z (high impedance) terminal This MF /HF antenna terminal is used to connect a high impedance antenna.

(38) LINE OUT (line output) jack This output has just the same function as that of the RECORD jack (14) on the front panel.

(39) EXT SP (external speaker) jack Used to connect an external speaker if necessary.

(40) SIDE TONE jack
Side tone input jack used when a transmitter is used in combination with the NRD-525.

(41) MUTE jack
Input jack for control of mute of NRD-525 when a transmitter is used in combination. If this is grounded during transmission shown in the following figure, the NRD-525 is muted (AF output is Cut Off).

(42) DC OUT (output) jack
The 10.8 V DC output jack. The output current capacity i: about 30 mA maximum.

(43) TIMER OUT (output) terminal
The relay contacts are output to allow the timer to control a1 external device.

Never connect an AC power source to this terminal.

(44) PRINTER connector
If an output is to be fed to the printer when the optional RTT) demodulator CMH-530 is used for reception of RTTY, the print must be connected to this connector. The printer used should b, . compatible with Centronics (e.g. one used for a personal corn putter).

(45) RTTY INDICATOR output
Output for mark and space signal indicator in case the optional RTTY demodulator CMH-530 is used for reception of RTTY. I can be connected the X and Y axes inputs of an oscilloscope t, display a cross pattern for precise tuning.

(46) DC power connector
Used when the NRD-525 is operated from a DC power source Connect the correct DC power cable to this connector. If any other cable is to be used , be sure to fit an in line fuse of 3A rating.

(47) RS-232C connector
This connector is used when the optional RS-232C interface unit CMH-532 connected to a personal computer is used to remotely control the NRD-525. This connector is attached to the CMH-532. It is not provided as a standard accessory.

(48) AC POWER connector
Used when the NRD-525 is operated from an AC power source.
Connect the correct AC power cable to this connector.

( 49) AC fuse, voltage selector
The 1 A fuse for AC power source, and selector for source voltage. The source voltage is selected from 100, 120, 220, and 240 V AC.

(50) VHF ANT connector
This antenna connector (50 11) is used to receive VHF band with the aid of the optional V  UHF converter CMK-165. It is attached to the V · UHF converter.

(51) UHF ANT connector
This antenna connector (50 ) is used when the UHF band is received with the aid of the optional V · UHF converter CMK-165. It is attached to the V  UHF converter.

5. OPERATION

For functions of switches and controls, refer to Chapter 4 “Switches and Controls on panels”.

5.1 Reception

This chapter describes fundamental use of the Receiver.

5.1.1 Preliminary Setting

When the antenna cable and power cables have been connected as shown in Fig. 3·1, turn on the POWER switch, and set the controls and switches as follows:

LOCK switch (5) ………… OFF
AF GAIN control (2) …………Tum fully counterclokwise.
RF GAIN control (7) ………… Turn fully clockwise.
TONE control (9) …………Neutral (central) position
NOTCH control (10) ……………… Turn fully counter clockwise.
SQUELCH control (11) ……….. Turn fully counter clockwise.
PBS (pass band shift) control (12) ………… set at Neutral position.
RIT switch (16) ………… OFF
ATT (attenuator) switch ………… OFF
NB LEVEL control (15) …………Turn fully counter clockwise.

5.1.2 Setting of Frequency

A frequency can be set by any of the following three methods :

• Setting of frequency with TUNING control (3) Any frequency in the entire receiving frequency range can be set in 10 Hz steps. Ordinarily, the TUNING control is used to change the frequency by less than 1 MHz.
• Setting of frequency with UP switch (4) or DOWN switch (6) Before use of these switches, turn on the FREQ switch (24). The frequency can be increased or decreased by the auto repeat function. These switches are helpful when you are going to search for signals in a relatively wide frequency range.
• Setting of frequency with numerical keys (28) To enter the frequency data with numerical keys, either of the following two methods are used according to the unit of the frequency (kHz or MHz) :

If you have pressed a wrong key, press the CLR key (31) and start again. Pressing the CLR key (31) before pressing I MHz I or I ENT / kHz I clears the data just entered and the pre setting of the frequency becomes valid. Once I MHz I or I ENT / kHz I key are pressed, CLR key becomes inoperative.

5.1.3 Reception of SSB Signal

The frequency of the suppressed carrier is indicated for both LSB and USB.

With the controls and switches set as described in 5.1.1, set the following controls and switches as specified :

MODE switch (27) ……….. LSB or USB
BANDWIDTH switch (26) ……….. INTER
AGC switch (24) ……….. SLOW
AF GAIN control (2) ……….. Set for suitable sound volume.
Receiving frequency ……….. Set to the desired frequency.

Slowly turn the TUNING control to find a point where the SSB signal can be clearly heard.

5.1.4 Reception of CW Signal

With the controls and switches set as described in 5.1.1, set the following controls and switches as specified :

MODE switch (27) ………. CW
BANDWIDTH switch (26) ………. INTER
BFO control (8) ………. Neutral position
AGC switch (24) ………. FAST
AF GAIN control (2) ………. Set for suitable sound volume.
Receiving frequency ………. Set to the desired frequency.

Receive the CW signal, and adjust the TUNING control (3) so that the AF (audio) output signal gives zero beat. Then, turn the BFO control (8) clockwise or counterclokwise to obtain desired note. The tone from the AF (audio) output  become about 800 Hz if the BFO control is turned clockwise or counterclokwise by 1.5 division on the scale from the neutral position.
If the optional narrow band filter is mounted on the NARR, put the BANDWIDTH switch (26) to the NARR position. Then, interference and noise will be reduced.

5.1.5 Reception of AM signal

With the controls and switches set as described in 5.1.1, set the following switches and controls as specified :

MODE switch ………. AM
BANDWIDTH switch (26) ………. WIDE
AGC switch (24) ……….  FAST
AF GAIN control (2) ………. Set for suitable sound volume.
Receiving frequency ………. Set to the desired frequency.

If the BANDWIDTH switch is put to the AUX position when
the optional narrow band filter is not mounted in the AUX position, the bandwidth will be set at 12 kHz and the quality of sound will be much improved.

5.1.6 Reception of RTTY Signal

The frequency indicated is the center frequency between the mark and space signals.

With the controls and switches set as described in 5.1.1, set the following controls and switches as specified:

MODE switch (27) ···············RTTY
BANDWIDTH switch (26) ··············· INTER
AGC switch (24) ··············· FAST
AF GAIN control (2) ··············· Set for suitable sound volume.
Receiving frequency ··············· Set to the desired frequency .

If you tune the receiver correctly to the center frequency of the transmitted signal, the center frequency of the AF (audio) output becomes 2210 Hz.

For operation and connection to get a printer output with the use of the optional RTTY demodulator CMH-530, see instruction manual for the CMH-530.

5.1.7 Reception of FAX Signal

The indicated frequency is the center frequency between the mark and space signals.

If you tune the receiver correctly to the center frequency of the transmitted signal, the center frequency for the AF (audio) output becomes 1.9 kHz.
To connect a FAX terminal, use the LINE OUT (output) jack on the rear panel.

5.1.8 Reception of FM Signal

The indicated frequency is the carrier frequency without modulation.

The FM signals which can be received in this mode are narrow band FM (with a frequency deviation of maximum 5 kHz). In this mode, the BANDWIDTH switch (26), and the AGC switch (24) are inoperative.

5.2 Use of Preset Memory

The NRD•525 can store 200 channels, with each channel containing the mode, bandwidth, attenuator on-off. and status of
AGC. What is stored is backed up by the lithium battery.

5.2.1 Setting of Channel

The channel is set by either of the following two methods:

• Setting of channel with UP switch (4) or DOWN switch (6) Before manipulating these switches, turn on the CHANNEL switch. IF the UP or DOWN switch is pressed. the channel number is increased or decreased.
• Setting of channel with numerical keys For example, the channel No. 199 is set with numerical keys as follows.

5.2.2 Storing

Data are stored by any of the following methods according to the order of setting of the frequency and channel number :

• To store the frequency first :

1. Tum on the FREQ switch (29), and set the frequency , mode, bandwidth, on- off of ATT, and AGC status which you want to store. (For setting of the frequency, see 5.1.2.)
2. Tum on the CHANNEL (30), and set the desired channel number. For example, the keys are used in the following manner to set the channel No. 199.
   Press the keys as : IT] IT] [}] Do not press the I ENT / kHz I key at the moment. If it is pressed, what is stored in the channel No. 199 is indicated on the vacuum fluorescent display (25), -and the newly set frequency, mode, bandwidth, on off of ATT, and status of AGC are deleted.
3. Press the ENT /kHz switch (33) with the MEMO (memory ) switch (33) depressed. Then, the beep sounds and what has been set is stored in the channel No. 199.

• To set the channel number first:

1. Turn on the CHANNEL switch (30), and set the desired channel number. (For setting of the channel number, see 5. 2.1.)
2. Turn on the FREQ switch (29), and set the frequency , mode, bandwidth, on- off of Attard AGC status which you want to store. (For setting of the frequency , see 5.1.2.)
3. Press the ENT / KHz switch (33) with the MEMO (memory) switch depressed. Then, the beep sounds and what has been set is stored in the desired channel.

5.2.3 Reception with Memory Channel

Turn on the CHANNEL switch (30) , and set the desired channel number. (For setting of the channel number, see 5.2.1.) When the channel number has been set, the data stored in that channel are displayed on the vacuum fluorescent display (25), and reception can be done according to the data. At this time, the characters “MR” (memory read) are illuminated. If the CHANNEL switch (30) is on, the channel number can be increased or decreased with the UP switch (4) or DOWN switch (6). If the FREQ switch is turned on, the frequency stored can be changed with the TUNING control (3), UP switch (4) and DOWN switch (6). In this case, the characters “MR” on the display disappears, and the newly set frequency is used for reception.

5.3 Scan and Sweep

The scan function allows automatic scan among specified channels. The· sweep function allows automatic sweep between specified edge frequencies.

5.3.1 Confirmation and Setting of Scan Start or End Channel

• SCAN START: Channel number at which the scan function starts scan.
• SCAN END: Channel number at which the scan function ends scan.

Press the SCAN switch (20) to select SCAN ST ART or SCAN END. Then, the previously set channel number and data stored in that channel are indicated on the vacuum fluorescent display (25), and reception can be done accorder to these data. To change the channel number setting, set the scan start or scan end channel number adoring to the procedures described in “5.2.1 Setting of Channel” after selecting SCAN START or SCAN END. Then, the set channel number and data stored in that channel are displayed on the vacuum fluorescent! display (25), and reception can be done according to these data. To exit and enter other operation, press either the CLOCK/ TIMER switch (19), SWEEP switch (21), FREQ switch (29), or CHANNEL switch (30).

5.3.2 Confirmation and Setting of Sweep Start Frequency or Sweep End

Frequency

• SWEEP ST ART: Frequency at which the sweep function starts sweep.
• SWEEP END: Frequency at which the sweep function ends sweep.

Press the SWEEP switch (21) to select SWEEP ST ART or SWEEP END. Then, the previously set frequency is displayed on the vacuum fluorescent display (25), and reception can be done at that frequency.

To change the frequency, select SWEEP ST ART or SWEEP END, and set the sweep start or sweep end frequency according to “5.1.2. Setting of Frequency”. Then, you can receive that frequency.

To exit and enter other operate on, press either the CLOCK/ TIMER switch (19), SCAN switch (20), FREQ switch (29), or CHANNEL switch.

5.3.3 Scan and Sweep

If the RUN switch (22) is turned on after the SCAN switch (20) is pressed to select and indicate SCAN ST ART or SCAN END, scan starts at the start channel number.
If the RUN switch (22) is turned on after the SWEEP switch (21) is pressed to select and indicate SWEEP ST ART or SWEEP END, sweep starts at the start frequency.

While sweep or scan is being executed, the characters “RUN” are illuminated on the vacuum fluorescent display (25). Upon this, the characters “START” or “END” disappears. To temporarily stop the scan or sweep function, press the RUN switch (22). To re-start scan or sweep, press this switch again. Then, scan or sweep re-starts at the channel number or frequency at which scan or sweep was suspended. If the SCAN switch (20) or SWEEP switch (21) is pressed during scan or sweep, SCAN START or SWEEP ST ART is selected, and scan or sweep is stopped.

During scan or sweep, the automatic pause can be set with the P· LEVEL (pause level) control (10).

If the P · LEVEL control (1 0)is turned fully clockwise, scan or sweep will be stopped by very weak signals. As the P· LEVEL centre! is turned counterclokwise, a stronger signal is needed to stop scan or sweep. In case the gain of the receiver is decreased with the RF GAIN control (7), automatic pause will not be effected unless the P· LEVEL control (10) is turned a little counterclokwise as compared with the full counterclokwise position of the RF GAIN control (7).

The scan or sweep speed can be set with the SPEED control (12). As the SPEED control (12) is turned clockwise, the scan or sweep speed increases.

CAUTION

1. During scan or sweep, the PBS (pass band shift) or notch filter does not operate.
2. After completion of scan or sweep, put the NOTCH control (10) to the OFF position, and put the PBS (pass band shift) control (12) to the neutral position.

5.4 Setting of Clock and Timer

The NRD-525 has two built-in clocks (CLOCK 1 and CLOCK 2). The power for the NRD-525 can be automatically turned on and off by the timer programmed based upon CLOCK 1. For simultaneous control of an external device, terminals connected to the relay contact are provided on the rear panel.

5.4.1 Display and Setting of Time

• Clock : Time such as local time
• CLOCK2 : Time such as UTC (Universal Coordinated Time)
• TIMER ON : Time at which the power for the NRD-525 is turned on when the CLOCK 1 indication reaches at the time pre-programmed.
• Tl MER OFF : Time at which the power for the NRD-525 is turned off when the CLOCK 1 indication reaches at the time pre-programmed.

Press the CLOCK/TIMER switch (19) to select either CLOCK 1, CLOCK 2, TIMER ON, or TIMER OFF. When it is selected, the time is indicated on the vacuum fluorescent display (25). At this time, the receiving frequency is not indicated, but reception can be done at the frequency already set before pressing of the CLOCK/TIMER switch (11). In this case, the settings concerning reception including the frequency, mode, and bandwidth excepting PBS and BFO (in the CW mode) cannot be changed. To change time, select the desired kind of time with the CLOCK/TIMER switch (19), and set the time with numerical keys in the following manner:

5.4.2 Calibrating CLOCK 1 within 30 Seconds

Press the CLOCK/TIMER switch (19) to select CLOCK 1.
While pressing the\ MEMO I switch (34), press the I ENT /kHz I switch (33) on the correct time (e.g. time broadcast).
Upon this, the digits of the second are reset to zero and the digits of the minute remain as they are if the digits of the second are between O and 29. If the digits of the second are between 30 and 59, the digits of the second are reset to zero, and the digits of the minute advance by “l”. At this time, CLOCK 2 is also calibrated automatically.

5.4.3 Use of Timer

As an example of the use of timer function. suppose that unattended recording is performed under the following conditions:

Receiving frequency: 12.3456 MHz
Recording time : From 7: 10 to 8: 20 according to UTc First, connect the tape recorder as shown in Fig. 5-2.

Steps of unattended recording

1. Set CLOCK 1 at the current time according to UTC (Use the current time according to local time if recording is to be done according to local time.)
2. Set TIMER ON time at 7: 00.
3. Set TIMER OFF time at 8: 20.
4. Set the receiving frequency at 12.3456 MHz. Set the mode, bandwidth, AGC, and ATT if necessary.
5. Put the POWR/TIMER ON-OFF switch (1) to the TIME position.
   (Then, the timer function begins to work.) At this time, vacuum fluorescent display (25) indicates the time  CLOCK 1 only, and only the DIMMER switch (17) remain effective.
6. Thus, setting is finished.
   When the TIMER ON time “7 : 10” has been reached, tile power for the NRD-525 is switched on, ancho recording started with the previously set receiving frequency, mod. bandwidth, AGC status, and on-off status of A TT indicate ‘ on the vacuum fluorescent display (25). When the TIM, OFF time “8: 20” comes, the power for the NRD-525 · switched off and recording is stopped.

5.5 Change of Operation by User Definition

Some operations of the NRD-525 can be changed by the user definition in the following manner.

• Frequency indication in USB/LSB mode
  Each time the numerical key [TI is pressed with the I MEMO I key depressed, the frequency indication in USB/LSB mode is changed in following manners :
  Indication shift Frequency indication is shifted by l.5kHz according to modes and output frequency of synthesizer is unchanged.
  Local shift Indication of frequency is unchanged but output frequency of synthesizer is shifted by l.5kHz according to modes. You can receive, without re-tuning, a lower or upper sideband of AM signal in LSB or USB mode respectively.

• Indication of 10 Hz digit of frequency
  Each time the numerical key [I] is pressed with the I MEMO I key depressed, the indication of the 10 Hz digit of the frequency appears and disappears in turn. Before shipment, setting is done so that the 10 Hz digit is indicated.

• Blinking of colon in time indication
  Each time the numerical key [JJ is pressed with the MEMO I key depressed, the colon blinks and ,stops blinking in turn. Before shipment, setting is done so that the colon blinks.

• Beeping upon pressing of key switch
  Each time the numerical key[}] is pressed with the I MEMO I key depressed, sounding of the the beep is set and reset in turn. Sounding of the beep upon erroneous key operation and upon storing of data cannot be reset. Before shipment, setting is done so that the beep does not sound when a key switch pressed.

• Bypass for input RF filters
  Each time the numerical key IT] is pressed with the I MEMO I key depressed, the input RF filters are bypassed and inserted in turn.
  When they are bypassed, characters “PASS” are displayed. If you wish to remove the loss due to the input RF filters while receiving very weak signal, you can use this command.

• Change of tuning step
  Each time the RUN switch is pressed, when the receiver is
  operated except SCAN/SWEEP mode (the indication of SCAN and SWEEP are off state), the tuning step is changed to fine step or course step in turn.

  • Fine step
    Tuning rate of the tuning knob is set to 2 kHz per revolution, and minimum increment step of the UP · DOWN switch is set to 1 kHz (5 kHz for FM mode).

  • Coerce step
    Tuning rate of the tuning knob is set to 20 kHz per revolution, and minimum increment step of the l :p DOWN switch is set to 10 kHz (same for FM model).

6. CIRCUIT DESCRIPTION

6.1 Outline

The block diagram and circuit diagram are respectively given in Chapters 10 and 11.

The NRD-525 can be broken down into the chassis, panel, receiver, synthesizer, and control blocks.

The chassis block consists of the power supply circuit, rear panel, and motherboard, which mutually connect various plug-in units. The power supply circuit feeds 5 V, 9 V, and 10.8 V to each unit.

The panel block has the controls and switches used for operation of the NRD-525. The large vacuum fluorescent display section indicates the frequency, mode, bandwidth, etc.

The receiver is of double super heterodyne type with a first IF frequency of 70.45399-70 .453MHz and a second IF frequency of 455KHz. The received signal from the antenna is applied to the electronic tuning circuit in the RF TUNE unit, where undesirable signal components are suppressed. The signal which has passed the RF TUNE circuit is fed to the first mixer through the RF amplifier. The signal is mixed with the first local oscillator (70. 543-104.453MHz) in the first mixer and converted into the first IF frequency of 70.45399-70.453MHz. This signal is mixed with the second local oscillate r of 69.99899-69 .998MHz and converted into the second IF frequency of 455kHz. The converted 455KHz signal passes through the IF filter, and is amplified and demodulated in the IF amplifier section. The demodulator SN16913 works as a synchronous detector in the AM mode, and works as the product detector in any other mode. In the FM mode, the FM detector MC3361 is used. The demodulated low frequency signal is amplified by the AF amplifier to a level suitable for driving the speaker.

The synthesizer block generates the first local oscillator frequency of 70.543-104.453 MHz, the second local oscillator of 69. 99899-69.998MHz, and BFO signal from the standard frequency of 12.8MHz.

The control block controls the panel, receiver, and synthesizer blocks with the aid of the microcomputer.

6.2 Units

The following plug-in units are provided as standard units.

1. HF tune unit CFL-205
   This unit includes the electronic tuning system, RF amplifier circuit, and a first mixer circuit.

2. IF filter unit CFH-36
   This unit includes a first IF filter (MCF), a second mixer l circuit, noise blanker circuit, and a second IF filter for the receiver block. The optional IF filter is mounted on this unit if necessary.

3. IF AF amplifier unit CAE-182
   This unit includes a notch filter circuit, IF amplifier circuit, AF amplifier circuit, FM detector circuit, AGC amplifier circuit, and squelch circuit for the receiver block.

4. Loop 1 unit CGA-131
   The unit generates the first local oscillator signal by a phase-locked loop (PLL) synthesizer. The signal covering 70. 543-104.453MHz in I-kHz steps is fed to the first mixer.

5.  Loop 2 unit CGA-132
   The unit generates the second local oscillator signal and BFO signal by a PLL synthesizer. The second local oscillator signal covering 69.99899-69.998MHz is fed to the second mixer. The frequency of the BFO signal varies according to the receiving mode in the following manner.

6. CPU unit CDC-353
   This unit includes the microprocessor and its peripheral circuits, which control the panel, receiver, and synthesize1 ·blocks.

7. Date 1/0 unit CMH-632
   The unit includes the standard oscillator (12.8MHz), counte1 for the synthesizer, and I/0 ports for the microprocessor.

7. ADJUSTMENT AND MAINTENANCE

The NRD-525 you have purchased is properly adjusted and strictly tested before shipment. Ordinarily, no adjustment is needed.
Detailed adjustments excepting adjustments described below require special expertise. So, whenever you think that the Receiver requires such adjustments, contact the nearest JRC dealer or branch.

7.1 Adjustment

1. Line output level adjusting hole
   Through this adjusting hole the output level of the LINE OUT (output) jack (38) on the rear panel. and the output level of the RECORD jack (14) can be adjusted a screw driver. Upon shipment, it is set at about DBM.(mW in 600 0)

2. Beep sound adjusting hole
   The beep sounds for warning if you Haye pressed an erroneous key during entry of data. Through this hole the sound volume of the beep can be adjusted with a screw driver. Set the sound volume at any value you want.

3. Monitor level adjusting hole
   The mute level in monitoring of your omen transmission can be adjusted through this hole.

4. Side tone adjusting hole
   Adjust the side tone input level in case the Receiver is used combinedly with a transmitter.

7.2 Maintenance

1. Parts
   Be careful in handling !Cs, transistors, and diodes because momentary short- circuiting will damage them.

2. Fuses
   If the power fuse has blown, trace the cause of the trouble before replacement. The AC power fuse is located on the rear panel. The DC power fuse is mounted on the power cable.

3. Lithium battery CR-2032FT6 (produced by Sanyo) It is used for backup of the memory channels. The life of the battery is about five years.

If the life of the battery has been expired, the contents in the memory become corrupted or it becomes impossible to store data in the memory during operation. In this case, replace the battery immediately. The model of the lithium battery is CR-2032FT6 (3 V).

If the battery is unavailable or you want to ask somebody to replace the battery, contact the nearest JRC dealer or branch.

• Replacement of lithium battery

1. Remove the power cable from the Receiver.
2. Remove the upper cover as shown in Fig. 9-1.
3. Remove the CPU unit CDC-353 as shown in Fig. 9-2.
4. Replace the lithium battery as shows in Fig. 7-2.
5. Put back the CPU unit CDC-353 to the original position by pushing it along the rail securely.
6. Replace the upper cover.

CAUTION

1. Note that the contends in the preset memory may be changed or lost after replacement of the battery.
2. In this case, please store data again referring to paragraph
   5.2.2.

8. TROUBLESHOOTING

The NRD-525 has so many functions that the user may make operational errors. Before concluding that the Receiver has failed, read through the operating procedures described in this manual.
Here, various phenomena caused by erroneous handling are discussed. They are not faults. Before asking for repair, find the cause and take proper measures. If the Receiver will not work normally even after that, contact the nearest JRC dealer or branch.

8.1 Simple Trouble

8.2 Complicated Trouble

8.2.1 Abnormal Indication and Abnormal Reception

If PCBs are disturbed during transportation, they will be improperly connected to the connectors on the motherboard, and abnormal indication, abnormal reception and various other troubles may result. In this case, remove the upper cover as shown in 9.1.l and fit each PCB securely by pushing it from above.

8.2.2 Entry of Noise into TV, Radio or Stereophonic Player

The Receiver is provided with sufficient electromagnetic shielding, but it may cause noise interference to other electronic devices due to incomplete grounding, or antenna location. In this case, take the following measures to prevent such interference.

1. Replace the grounding conductor with a thicker and shorter one, and connect it to the nearest water pipe or copper plate buried under ground.
2. Put the antenna for the electronic device being interfered with away from the antenna of the NRD-525.
3. If the affected device is a TV or FM receiver. adjust the direction of its antenna or replace the antenna with one having better performance.
4. Take the power for the Receiver· from some other plug receptacle.
5. Replace the grounding conductor for the affected device with a thicker one.
6. Mount a noise filter or isolation transformer on the power line.

8.2.3 Entry of Artificial Noise into Receiver

In addition to pulse noise due to lightning, rain, or snow, noise from a transmission line, high frequency sewing machine, personal computer, fluorescent lamp, hair dryer, etc. may affect the receiver. If there is any other transmitting antenna near the receiver. Noise may come only when that transmitter is working.

Fundamentally, such artificial noise must be eliminated by correction made on the part of the noise source. However, noise may be sometimes eliminated by change of the shape or location of the receiving antenna for the NRD-525 complete grounding may eliminate noise.

If the field strength of the desired signal you want to receive is sufficiently high, no noise will interfere with your reception.

8.2.4 Interference due to intermodulation

In an area where several medium-frequency broadcasting stations which emit strong carriers are located, broadcasting from more than two stations may be received at a time at such a frequency that should not allow reception of these stations. This phenomenon is called intermodulation. If there seems to be intermodulation, turn on the A TT switch on the Receiver. If this will not eliminate interference, decrease the antenna height or shorten the antenna. Then, trouble will be eliminated in most
cases.

8.2.5 Too Low Sensitivity of Receiver

In the HF band, the field strength for the signal from the same station greatly changes according to the frequency, time, season, and number of sunspots. To compare the sensitivity of receivers, they must be connected to the same antenna and tuned to the same frequency at the same hour, then the S/N ratio of two receivers may be compared.

Also, the sensitivity may depend on the sound quality of the speaker. If you feel that the sensitivity of the Receiver is low, confirm the selection of the frequency and directivity of the antenna.

9. OPTION

9.1 Option

For additional convenience and effective use of the NRD-525, the following options are available:

■ RTTY demodulator unit CMH-53O
This unit allow reception of RTTY and printing the received messages on the printer.
Shift width :
Transmission rate : ±85Hz,±200Hz,±425
Hz(selected with numerical keys on the front panel) 45.45 or 50 Bauds(selected with numerical keys on the front panel)

NOTE : The printer must be provided by_ the customer at his own cost if necessary.

■ RTTY connection cable 6ZCJDOO139
This is a cable to connect the NRD-525 and the printer. connector of printer side has 36 pins.
■ RS-232C interface unit CMH-532
This is used to remotely control the N RD-525 from an external device (such as personal computer).
IIRS-232C connection cable 6ZCJDOO140
This is a cable to connect the NRD- 5~5 and external de\’ice (such as a personal computer).
Connector of external device side has 25 pins.
■ IF filter
This is a narrow band crystal filter.
The following types are available :
CFL-23l(YF 455FM) —6dB bandwidth 240Hz or more
CFL-232(YF455DQ) – 6dB bandwidth 0.5-0.8k Hz
CFL-233(YF455DE) —6dB bandwidth lKHz-l.5kHz
CFL-218A(YF455EBF) -6dB bandwidth 1.7-l.9kHz
■ Speaker NVA-88
This large type speaker has a design matching that of the receiver.
1B Headphone ST-3
Specially designed for communication use.

9.2 Installation of Options

Before starting work, be sure to remove the power cable. Do not remove units unless absolutely necessary.

1. Removing cover
   As shown in Fig. 9-1, remove the upper cover or lower cover by loosening four screws. The spiker is mounted on the upper cover. Remove the upper· cover slowly, taking care not to break the speaker cables. Remove the connector at the end of the cable from the internal unit if necessary.

2. Removing internal units
   Each unit is located as shown in Fig. 9-3.
   (2) From the parts mounted side, insert the removal levers’ supplied with each option into the holes at both corners of the PCB.
   (2) Lower the removal lever carefully so as to lift up the PCB._
   (3) When the PCB has been removed from the connector, lift it slowly to remove it.

3. Mounting of IF Filter

A total of two filters can be mounted additionally in the IF filter unit CFH·36 corresponding to the  and AUX of the bandwidth switch.

1. Remove the upper cover.
2. Remove the IF filter unit CFH-36 from the Receiver.
3. Mount the IF filter as shown in Fig. 9-4.
4. Exchange jumper wires as shown in Fig. 9-5.
5. Put back the IF filter unit CFH-36 to the original position by securely inserting it along the rail.
6. Mount the upper cover.

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