General
General construction and
operation of JUMA-TRX1 DDS is same or similar compared to JUMA-RX1 and
TX1 DDS boards. Additional information can be found from JUMA-RX1 and TX1
documentation. Understanding how JUMA-TRX1 DDS module (hardware and software)
works can be gained by reading JUMA-TRX1 software v1.00r source code comments.
DDS-and-control section
adjustments
The DDS section doesn’t
necessarily require adjustment. However, the frequency of the LO and hence
also the frequency precision of the RX depend on the frequency of the reference
oscillator.
Reference oscillator adjustment
(C20)
For adjusting the reference
oscillator, a special adjustment mode is included in the program suite.
If the pushbutton switch of the encoder is kept depressed during start-up
of the device, it will enter the adjustment mode. To indicate this mode,
the display will show 1 MHz. In this mode, the setting of the DDS is an
exactly calculated number corresponding to 1 MHz output frequency. While
in this mode, the frequency generated by the DDS is measured with a precision
frequency counter or other similar means, and it is adjusted in place with
trimmer capacitor C20, affecting the frequency of the reference oscillator.
Powersupply voltage display
calibration (R23)
Due to stepped values and
varying precision of resistors and to distribution in the precision of
+5V regulators, the displayed value of supply voltage probably isn’t quite
accurate. The display can be adjusted to be "on the nose" by adding a suitable
resistor in parallel with R23 (910R). A suitable value can be found by
temporarily soldering eg. a 100 k trimmer in parallel with R23. When the
voltage display is accurate, the trimmer can be replaced with nearest standard
value resistor.
LCD display contrast (R2)
LCD display contrast is
set by voltage present in pin #3 of the display module connector. This
implementation uses one 1k8-ohm resistor (R2) to set the voltage. The voltage
producing "suitable" contrast depends on display module type, production
lot, and to a lesser degree, on temperature of operation. If you use a
different type display than the one in parts list, or if the contrast is
not satisfactory, it can be adjusted by changing the value of R2. Lowering
the value will make the display darker and increasing it will make the
display lighter. Adjustment range is between zero and a few kilo-ohms.
A suitable value can be found by soldering a temporary eg. 5k trimmer in
parallel with R2
Operation checks
Before use some operation
checks may be done to ensure perfect operation of JUMA-TRX1 transceiver.
CW shift signal
Grounding J1-1 should decrease
selected frequency by 700 Hz. This change is also visible in frequency
display.
Band select output
Voltage on J7 should be
0V when selected frequency is bellow 4MHz. Voltage on J7 should be 5V when
selected frequency is over 4MHz. If PA board is connected you should also
hear band select relay RL2 operating when you tune back and forth over
4.000.250 Hz
Software setup options
(software version v1.00r)
To enter operating mode
setup select keep encoder pushbutton switch pressed during startup and
five seconds after you see 1 MHz adjustment mode indicator on the display.
After five seconds Mode X text appears on the display. Yet keep encodes
switch pressed and select desired operating mode by turning encoder. Operation
mode selection bits are represented with numbers 0 to 7. Releasing encoder
switch saves selected operating mode to EEPROM memory.
Operating mode bits
D0 select RIT(default, D0=1)
or A/B VFO mode. In RIT mode grounding J9 turns RIT on. In A/B VFO mode
grounding signal J9 selects B-VFO.
D1 and D2 select start up
sound message (default short beep D1&D2=1).
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Start up sound |
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No sound |
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No sound |
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Morse TRX1 |
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Morse TRX1 |
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Morse JUMA …. QRV |
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Morse JUMA …. QRV |
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Short Beep |
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Short Beep (default) |
Note!
If you use two VFO seutp (A/B), connect the RIT switch wire
to the GND instead of the TX signal (keep the other wire in J9). In this
case the RIT switch will be VFO select switch. see
Wiring Diagram.