Vectronics VEC-131K - Manual (Page 24)

VEC-131K Owner's Manual Aircraft Receiver Kit
22
! Watch for parts installed in the wrong spot! These errors must be corrected
before attempting to align or use the kit.
Now that assembly and inspection is completed, you're ready to begin the testing
and alignment phase of construction.
TESTING AND ALIGNMENT
There are two critical alignments points in this receiver: the local oscillator (LO)
and the 10.7-MHz IF. The LO is set by adjusting coil L4. The 10.7-MHz IF is
tuned by coil L5.
The IF stage alignment must be performed before LO alignment.
10.7-MHz IF Stage Alignment Using a Signal Generator
Initial VEC-131K control settings:
•
Set the volume control to midrange.
•
Set the tuning control fully counterclockwise (CCW).
•
Install a 9-volt alkaline battery on the VEC-131K battery clip.
•
Install a 4 to 8-ohm monitor speaker (with a 1/8” plug) into the VEC-131K
audio jack.
Set the generator as follows:
•
Frequency.................................10.7 MHz
•
Modulation ...............................AM, 1000 Hz at 30% depth
•
RF output level .........................-10 dBm ( .1 volts)
1. Connect the signal generator output to the RCA antenna jack on the VEC-
131K.
2. Preset the tuning core for coil L5 fully counter-clockwise (CCW).
3. Turn the VEC-131K receiver on by depressing the SW1 shaft.
4. Slowly adjust the tuning core for L5 in a clockwise direction until the 1000
Hz modulation tone is heard in the speaker. Peak L5 for loudest signal.
5. Rock the main tuning control. This should have no effect on the IF signal. If
the signal vanishes, you have tuned to a harmonic of the signal generator that
falls in the aircraft band. Set the tuning control so no signal is heard, and
retune L5 again.
6. Reduce the signal generator RF output level by another 10 dB, or until the
audio tone becomes very weak. Repeak L5 for loudest signal.