ILER-20 MK2 SSB QRP Transceiver Kit
Page 27
ADJUSTMENTS AND TESTS
Preliminary Testing
- Adjust P3 (carrier suppression), P4 (volume potentiometer), and P5 (bias adjustment) to mid-position.
- Adjust P2 (mic gain) to minimum position (counterclockwise).
- Connect a speaker or headphones to the “ALT” pins on the circuit board.
IMPORTANT: Use a high-quality speaker box. A bad speaker will make ineffective the operation of the
transceiver.
- DO NOT yet connect a microphone.
- Apply power supply voltage (12-14V) to the “12V” header pins on the circuit board.
- Measure the voltage at the following main points:
Rx-Tx LED illuminated green (some LED's have the leads reversed; turn it around if it is red in Rx).
8V on any lead of L5 or L7 to ground.
6V on any lead of L2 or L3 to ground.
- Turn the volume to maximum; you should hear a hissing noise in the headphones or speaker.
If everything is okay, you may continue.
If something is not right, you will need to examine it. (see the section, “If your kit does not work after
assembly").
Adjustment of the VXO Tuning Inductor L6 and Polyvaricon CV2/CV3
The following work is usually more enjoyable than what it appears at first; it is not “plug & play”. Look for
a few hours when you are not in a hurry. Take your time and enjoy yourself!
Solder the pigtails of L6 in place on the circuit board. Leave them a little long (5-6mm) for the moment,
so that you can compress or spread the turns. Connect a frequency counter to the “VXO” header. If the
input of the frequency counter is low impedance, insert a 470 ohm (or greater) or a small value capacitor
(try with 22pF or less) between the frequency counter and the header to reduce the interaction with the
VXO.
If you don't have access to a frequency counter, you may use a high-quality SSB or CW receiver that
covers the VXO frequency (11.000MHz) and that has digital frequency readout. Connect to the receiver
antenna input a piece of wire with a small loop and place it close to the VXO.
Note: Use of a frequency counter is highly recommended for this adjustment, as the use of a receiver is
very cumbersome.
The IF frequency of 3.276MHz is added to the VXO frequency, for example of 11.000MHz, to obtain the
operating frequency of 14.276MHz (VXO crystal option=11.000MHz). Another example would be IF
3,276MHz and VXO 11.040MHz = 14.316MHz (VXO crystal option of 11.048MHz).
Spreading or compressing the turns changes the range of coverage. Compressing the turns increases
the inductance, thus increasing the frequency range. If the turns are spread, the inductance and thus the
frequency coverage decreases. Spreading or compressing the turns very little achieves a variation of a
few Khz.
The polyvaricon contains two variable tuning capacitor sections. J1 selects which section is used.
Placing jumper “B” selects the section with more capacitance, CV2 (160pf); placing jumper “A” selects
the section with less capacitance, CV3 (70pf).
The following illustrative table uses
J1
with a jumper in
position B
and the
turns on L6
moderately
compressed (this is the configuration that I recommend for the ILER-20):
For the ILER-20, jumper J1 should be placed in position B.
