ILER-40 MK2 SSB QRP Transceiver Kit
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Adjustment of the TX passband, T3 and T4
Note: For this adjustment you will need an “alignment” tool suitable for this type of coils; if you use a
screwdriver, you risk of breaking the core of the coil.
Connect a power meter with a 50 ohm load to the antenna jack.
I suggest two options for adjusting the transmitter passband:
1) If you have access to an audio generator, set the mic gain (P2) to half range and injects a signal of
around 800-1000Hz. at about 20mV into the mic input; put the transceiver in transmit mode (PTT pin to
“GND”) and alternately adjust T3 and T4 until obtaining to the maximum power reading on the power
meter.
2) If you don't have access to instrumentation, connect a wire from header pin “K1” to po12V and
puts the transceiver in transmit (pin PTT to GND). This will cause the modulator to generate a carrier;
alternately adjust T3 and T4 until obtaining the maximum power level possible on the power meter
(you
will not obtain the maximum power until connecting the microphone).
After finishing the
adjustment, disconnect the wire from pin “K1”.
Adjustment of the Balanced modulator (carrier suppression)
Adjust P2 (mic gain) to minimum (counterclockwise). Adjust P3 to mid-position.
Connect the power supply. Let the transceiver warm up for about 5 minutes.
Now, activate the PTT pin of the mic and monitor the transmitter output with an oscilloscope (with a 50
ohm load connected). Adjust P3 to obtain the minimum level possible of residual carrier signal.
If you don't have access to an oscilloscope, you may listen to the transmitted signal on a SSB/CW
receiver; adjust P3 until you hear the least possible amount of carrier signal. Keep in mind that with a
receiver so close, you will ALWAYS hear a weak residual signal.
IMPORTANT:
The ILER-40 mic input is quite sensitive and offers very comfortable operation and good
modulation quality. Use of a classic dynamic microphone, such as those used for CB's, is recommended.
In order to use an electret microphone, a small adaptor circuit will need to be used (see the Appendix in
the additional documentation).
The use of amplified microphones is not recommended.
Just as choosing a good speaker is important for reception, be careful with the type of microphone that
you use and with the gain adjustment; an unsuitable microphone or excessive gain can ruin the
transmission quality.
Adjustment of mic gain P2
Adjustment with instrumentation.
Connect the 50 ohm load and power meter to the antenna jack. Adjust P2 (mic gain) to its mid-position.
Connect the microphone to the mic input and press the PTT to go to transmit. (TX = PTT to “GND”)
Connect an oscilloscope to the antenna jack (along with a 50 ohm load). Adjust the transceiver to see
the signal envelope and, speaking loudly into the microphone, adjust P2 just to the point before seeing
distortion on the waveform.
