miniPIG-10 Alignment
with 50 ohm dummy load attached to antenna
XTAL FILTER CENTER FREQ
Since most everything on the miniPIG is adjustable EXCEPT the crystal filter,
we need to align everything around the filter center frequency. The only way
I know of to find the center frequency of the filter is to inject a low level
RF signal (less than 1 MV) on the input to the filter and sweep the RF frequency
from 8,063 to 8,065; then measure the output at either the input or ouput of the
IF amplifier and look for a peak reading. The peak should be near 8,063.5 KHz.
Write the number down - very important!
PREFERED AUDIO FREQ for CW
Decide what audio frequency you like to listen to the best.
A common audio frequency is 600 Herz. Write it down.
The next step is 2nd grade math - need help? - email me!
CALCULATE the BFO Xmit & Rcve FREQUENCIES
BFO frequency for receiving is XTAL_CENTER_FREQ + AUDIO_FREQ
8,063.5 + 600 = 8,064.1 KHz for receive.
BFO frequency for transmitting is the XTAL_CENTER_FREQ
8,063.5 for transmit.
Adjust C81 and C82
Place a frequency counter on the output of the BFO.
A good place to measure is at the junction of D11 and D10.
While the miniPIG is in receive mode, adjust C81 for 8,064.1 KHz.
Place the miniPIG into transmit mode and adjust C82 for 8,063.5 KHz.
There may be some interaction between adjustments, so repeat these
steps 2 or 3 times until you have the desired frequencies.
ADJUST TRANSMIT BandPass FILTER
Place an oscilloscope probe at the emitter of Q7. Adjust C49 and C50
for maximum and purest / cleanest signal.
Try to minimize any fuzzyness observed on the signal peaks.
ADJUST TRANSMIT OUTPUT POWER
Place a wattmeter between the output and the dummy doad. Adjust R25 for
1 watt output.
ADJUST RECEIVER
Peak all remaining adjustments for maximum received signal.
