ILER-40 MK2 SSB QRP Transceiver Kit
Page 30
- Adjustment with instrumentation (requires a frequency counter):
Turn on the transceiver. Leave it on for about 5 minutes. Connect the frequency counter to the “BFO”
header. If the input of the frequency counter is low impedance, insert a 470 ohm (or greater) resistor or a
small value capacitor (try 22pF or less) between the frequency counter and the header to reduce the
interaction with the BFO.
Adjust CV1 for a frequency of 4.913.5 MHz. You may readjust it slightly later if needed.
The total range of the CV1/BFO is approximately 4.912.8 to 4.914.5 MHz. The capacitance of the
trimmer goes from maximum to minimum in a ½ turn (180 degrees). If you look inside the adjustment
hole, you will see that there is an arrow to one side or other of the travel. When the arrow points to the
flat part of trimmer, the capacitance is at minimum.
Note: The BFO adjustment is important for reception, but even more so for transmission, as it
substantially influences the modulation quality as well as the output power. The signal may sound too
sharp and tinny or very bassy and muffled.
Adjustment of the RX pass band, T1 and T2
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.
With an antenna connected to the transceiver, alternately adjust T1 and T2 until obtaining the maximum
level of noise in the speaker. Now, try to tune in a stable signal within the band and readjust T1 and T2
alternatively until you hear it at the highest possible level.
If you have access to an RF generator, begin injecting a signal of about 1uV within the frequency
coverage of receiver and tune it in. Reduce the level of the RF generator to the minimum that is still
audible with a loudspeaker or headphones, and alternately adjust T1 and T2 until obtaining the
maximum reception level.
Once you have finished all of the adjustments and tests for the ILER-40, you may make a slight
readjustment of the reception if you wish.
REMEMBER: All transmission tests should be done with a 50 ohm load connected to the
transmitter output. DO NOT OPERATE the transmitter without a heatsink attached to Q14.
Adjustment of the idle current of the TX output transistor Q14
Although this adjustment is not critical, it is important to do it with the transistor cool.
Adjust P2 (mic gain) to minimum position (counterclockwise). Remove jumper J2. Adjust P5 (“BIAS”
adjustment) to the center of its range.
Connect a multimeter in its position for measuring current on the 200mA scale in series with the pins of
J2. Activate the PTT or put a jumper between the PTT pin and ground; adjust P5 to obtain about 45mA
on the meter.
As transistor Q14 is heating up, it is normal for this value to increase.
If you don't have a meter for measuring milliamperes, adjust P5 to about 75% of its range (going
clockwise); this position will be within the correct margin.
After finishing the adjustment, return jumper J2 to its position and readjust P2 (mic gain).
