Vectronics VEC-131K - Manual (Page 25)

VEC-131K Owner's Manual Aircraft Receiver Kit
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7. Once L5 is peaked, the 10.7-MHz IF alignment is completed. Turn the
receiver off by pushing SW1, and proceed to the LO alignment.
10.7-MHz IF Stage Alignment By “Ear”
1. Set the VEC-131K volume fully clockwise (CW).
2. Set the tuning core in coil L5 fully counter clockwise (CCW).
3. Connect a speaker and fresh 9-volt battery to the receiver, and turn on the
receiver using SW1.
4. Slowly adjust coil L5 in a CW direction until a rushing or hissing noise is
heard in the speaker or headphones. Repeak L5’s tuning until you find the
point where the rushing noise is loudest. Reduce volume setting as needed.
5. Proceed to the LO alignment.
Setting the Local Oscillator Tuning Range Using the Signal Generator
The typical tuning range of the VEC-131K is from 118 to 136 MHz. Depending
on individual construction techniques and parts tolerances, some receivers may
not reach much above 134 or 135 MHz. This is a design tradeoff that ensures
every kit will tune--with ample overlap--to at least 118 MHz. Most air-comms
take place in the lower portion of the band.
Set the generator as follows:
•
Frequency.................................118 MHz
•
Modulation ...............................AM, 1000-Hz at 30% depth
•
RF output level .........................-80 dBm (30 micro volts)
1. Connect the signal generator to the VEC-131K RCA jack using 50-ohm
cable.
2. Using a hex-alignment tool, adjust the core for coil L4 until it is level with
the top of the can.
3. Set the VEC-131K volume control midrange.
4. Set the VEC-131K tuning control fully CCW (counterclockwise).
5. Power up the receiver.
6. Insert a hex-alignment tool into the tuning slug for coil L4. Slowly turn the
slug in a clockwise (CW) direction until the signal generator signal is heard
in the speaker. Go slowly, the tuning is rather rapid and the signal may be
easily missed.
Setting the Local Oscillator Tuning Range Using a Frequency Counter