PENNTEK TR-35 CW Transceiver Kit Instruction Manual
- June 9, 2024
- PENNTEK
Table of Contents
TR-35 CW Transceiver Kit
Instruction Manual TR-35 Operating Instructions 05/10/22 V0.27
TR-35 CW Transceiver Kit
The TR-35 is a 4-band 5-watt CW transceiver covering the 40-, 30-, 20-, and
17- meter bands with generous receiver tuning ranges above and below each
band. Selectable receiver modes allow for narrow band CW, wideband CW, and SSB
reception.
Front Panel Controls
Refer to the front panel for the location of the switches and controls. The
four rotary controls are pretty much self-explanatory. There is a keyer speed
control (5-45 WPM) on the left, then the TX Power (0-5W) adjust pot, an RF
gain control, and a volume control. The power on-off switch is at the upper
left, the Receiver Mode / AUX switch is in the middle, and the Band selector /
RIT switch is to the right. The two right-most switches are 3-position spring
return toggle switches.
Band Changes and Memories
To change bands, momentarily flip this switch upward and allow it to return to
the center off position. Do this quickly, and the unit will consecutively
switch from one band to another. If you flip the switch up and hold it up for
a short while, the current frequency and receive mode will be stored in a
semi-permanent memory.
The display will momentarily switch to a reverse optical mode to show that the
current frequency has been stored. There is a separate memory for each of the
four bands. To recall this memory, 2 quick successive upward clicks are
required.
RIT Function
To engage the RIT function with this switch, a quick downward push and release
of the toggle is needed. The orange RIT warning LED will come on, and the
display will read out the offset with 10 Hz resolution as you tune. Another
quick downward toggle will dis-engage the RIT function. The Dial Lock function
is also controlled with the RIT switch by using a longer engagement time of
about 1.5 seconds. This will prevent tuning and band changes. To exit the lock
condition, another longer switch activation is required.
Receiver Modes
The Receiver Mode switch will toggle between Narrow Band CW and Wide Band CW
with quick upward click of this switch. A longer click will engage SSB mode.
The receiver IF bandwidth will be changed to accommodate the selected mode,
and the display frequency reading will maintain calibration when switching
between CW and SSB modes.
AUX Switch
The AUX switch is used to activate the keyer record/playback functions. A
quick switch activation will select the playback mode, and a longer switch
closure will enter the record mode. The keyer playback or record mode can be
exited by a short press of the AUX switch. (See below for complete
instructions for the keyer memory operation.)
Tuning and Step Size
The knob to the right of the blue OLED display is the tuning encoder. The
frequency may be change in 10 Hz, 100 HZ or 1 kHz steps. The tuning encoder
will tune at 40 steps per revolution, allowing tuning rates of 400Hz, 4kHz, or
40kHz per revolution. The tuning step resolution is selected by a momentary
switch attached internally to the tuning encoder. Short pushes on the tuning
knob will alternate between 10 and 100 Hz tuning steps. A long press will
enable 1 kHz steps. The frequency readout on the display will show the tuning
resolution selected with an underline bar beneath the digit selected. There
is lots of tuning range above and below the selected amateur band for SWLing.
The transmitter will not operate-out of-band and will display an “OOB” warning
if this is attempted.
Panel LED Functions
The blue LED Signal indicator can be used to judge the strength of the
received signal. A bright blue LED would indicate a strong signal. The red LED
is the battery low-level warning indicator. It will blink when the battery
voltage drops below a preset level. The warning level is internally adjustable
from 9 to 11.5 volts.
Phones, Power, and Key Jacks
An external speaker or headphones can be connected to the “Phones” jack on the
right side. There is more than ample audio available. Power is connected to
the DC input connector on the left side. The power plug body size is 5.5mm and
the center pin size is 2.1mm with positive polarity The voltage should be
between 9.5 and 14 volts. The key jack and keyer paddle jack are on the left
side. Both may be connected and used randomly as you desire. This way, you are
always ready for a new “SKCC” contact, as there is no need to reboot the
transceiver in order to change from the keyer using paddles to a straight key.
Transmitter Operation and Final FET Protection
The transmitter output power is adjustable from a few milliwatts to 5 watts or
more depending on the power supply voltage. It should be possible to achieve
the “1000 Miles per Watt” award with a station a few miles away by turning the
power output down to a few milliwatts while maintaining contact! With a
12-volt supply, the output is at about 5 watts into a 50-ohm load. The final
TO-220 RF transistor is durable and has survived delivering 5 watts continuous
key-down periods of more than 5 minutes during product development. The TR-35
transmitter is designed for CW duty cycle use only. Although the final FET
amplifier is rugged and robust, it is not intended for extended periods of
continuous key-down operation at maximum output, especially at higher DC
inputs. Attempting to do so will activate a power fold-back circuit designed
to prevent excessive heat build-up in the final RF amplifier FET. A poly-fuse
device reacts to the current drawn by the transmitter and will slowly but
temporarily increase its resistance over time and temperature, thereby
reducing the RF power output. This power reduction occurs only with extended
key-down operation, particularly with higher DC input voltages. At the
extreme, power output could drop to zero with the receiver becoming
inoperative as well. The poly-fuse is selfresetting if power is removed, and
the poly-fuse
is allowed several minutes to recover. Normal CW operation will not activate
the power fold-back circuit, but key-down times of 10 seconds at maximum power
might, particularly at higher DC input voltages. If you need more than 5
seconds or so of RF to make an antenna adjustment, simply turn down the RF
power output for these adjustments. Not only will this step prevent activation
of the final FET fold-back circuit, but it will also reduce QRM on the
band,which is always good operating practice. The polyfuse is also critical to
the operation of the reverse polarity protection circuit.
Sidetone Zero-Beat
The side-tone that is heard while transmitting is the actual transmitted
signal being heard by the receiver. If you match the audio tone of the
received signal to the tone of the side-tone, you are guaranteed to be at zero
beat with the station you are communicating with.
How to use the Keyer Record and Playback Functions
The record and playback functions are initiated with the “AUX” switch. There
are two message memories provided. Each can store 25 words using the “PARIS”
standard, or 125 ASCII characters if stored with no word spacing. This should
be plenty for POTA or SOTA activations. Before starting to record, set the
keyer speed control to a comfortable setting. A little slower than normal
might be better. Don’t adjust the speed control while in record mode. To
record a memory, activate and hold the “AUX” switch for about 1.5 seconds. The
OLED display will show the record menu. Choose message 1 by tapping the “DIT”
paddle, or message 2 by tapping the “DAH” paddle. The TR-35 sidetone will
immediately respond by sounding a “1” or “2” in morse. If the sidetone sounds
a little “clicky”, turn down the RF gain control some. After the morse number
is finished playing, you may record your message using the paddles. You can
abort a record session by activating the “AUX” switch. The transmitter will be
inhibited while you record your message. When your message is finished, simply
stop sending, and the recording session will time out after about 3 seconds
and the TR-35 will revert to regular transceiver mode. To Listen to, or play
back your message, activate a short “AUX” switch closure. The playback menu
will appear on the display. Be aware that the transmitter will be active while
playing back a message, so remember to turn down the RF power control while
checking your recorded message. Message 1 is selected by tapping the “DIT”
paddle and message 2 by tapping the “DAH” paddle. The selected message will
immediately start to play and will play to the end. To stop the playback at
any time, tap either the DIT or DAH key. An “AUX” switch activation will also
abort a message playback. The volume control must be up to hear a message.
Reverse Optic Display Mode
Better display visibility in bright light conditions may be possible by
reversing the display optics, that is, black numbers on a blue background. To
do this, the TR-35 is turned on while the receiver mode switch is engaged and
held until the display shows solid blue. Changing back to normal optic mode
requires a power reset without the receiver mode switch engaged. Note that the
reverse display mode consumes about 10ma more current from the battery.
Internal Adjustments
There are five internally accessible adjustments: PA Bias, sidetone level,
signal level LED sensitivity, audio bandpass filter frequency, and low battery
detector threshold. The PA bias normally shouldn’t need adjustment except at
initial build.
If your TR-35 is factory built, it would be rare that this control ever needs
adjustment, other than if the final RF output transistor should need to be
replaced (which would also be rare). The sidetone level pot may be adjusted to
set the level your liking, and the low battery level pot can be set to a level
consistent with the battery type you use. This level is usually set to about
9.5 volts on factory wired units. To access these adjustments, the plastic
case bottom must be removed. To do this, remove the four black screws from the
case front panel, and remove the board set along with the case top half by
lifting on the left side of the panel and maneuvering the BNC connector
through its exit hole. All five internal adjustments will now be accessible.
The sidetone level adjustment control is labeled on the left side of the lower
board next to the power jack. The PA bias and battery detector adjustments are
labeled on the rear of the lower board. To set the low battery point, adjust
the input DC voltage to the battery voltage you wish to have the alarm flash,
and adjust the low battery pot until the red LED alarm LED blinks. Be careful
not to adjust the bias pot by mistake! See the on-line building procedures for
instructions on setting the PA bias. The blue signal strength LED sensitivity
pot is located between the bias and battery voltage warning adjustment pots
and is attached to the upper board. Normally the pot is set for a faint glow
of the blue signal quality LED with the RF gain control fully
counterclockwise. The audio bandpass filter adjustment is labeled on the lower
board at the front of the unit. The pot is adjusted for maximum sidetone audio
volume while in narrow CW mode. This will be very close to the center of the
rotational range.
TR-35 Connector Wiring
Key Jack: T he Key jack will work with either a mono or a stereo 3.5mm
plug. The tip and ground shell connections are used. There is no connection to
the Key jack ring terminal inside the TR-35
Paddles Jack: The Paddle jack requires a stereo 3.5mm plug. The tip is
the “DIT” connection, and the ring is the “DAH” connection. The shell is the
ground.
Note that you may connect both a straight key and paddles and use either at
any time. No need to reboot the transceiver to switch from one to the other.
You’re always ready for an unexpected “SKCC” contact with the straight key!
DC Power Jack: This requires a standard 5.5mm plug with a 2.1mm center
pin diameter. The polarity of the center pin is positive.
Phones
Jack: The Phones (speaker) jack on the 02/2022 Rev B upper board is wired
for a standard 3.5mm mono plug (tip and ground). If you connect a standard
stereo headphone, only one earpiece will play. Use a 3.5mm mono to stereo
adaptor if you wish both earpieces to play. These adaptors are available from
eBay and Amazon. There is a simple modification you can make that will allow
both headphone earpieces to play, but only if you never intend to use a mono
plug connected to the “Phones” jack. To make this mod, the top case half must
be removed by removing all the knobs and the four nuts holding the case half
to the board assembly. Remove the four black case screws and lift off the
upper-case half. Carefully solder in a jumper wire as shown in yellow in the
photo. Once this modification is performed, do not connect a mono plug to the
phones jack. Additionally, do not perform this modification on earlier upper
PC boards labeled “Rev A3 12/2021” in the upper right corner of the board!
Doing so will cause destruction of the audio output amplifier. The phones jack
on these earlier boards is wired differently than the newer ‘Rev B 02/22
boards.
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