Vectronics VEC-102K - Manual (Page 29)

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Dial Calibration Adjustment of Trimmer Capacitor C5
Trimmer capacitor C5 is provided to help you match actual tuning to the panel calibration
as closely as is reasonably possible. Adjustment consists simply of matching a signal of
known frequency to its correct position on the dial. The reference signal can be generated
with test equipment, or it can be a distant station of known frequency, or you can listen
for the regenerative oscillator on another nearby receiver.
The precision broadcasts of Station WWV at 10.0 and 15.0 and 20.0 MHz are the most
easily identifiable reference signals. First, try for the 10.0 MHz transmission. With the
bandswitch set to C, tune carefully from 10 MHz down to the far left of the scale and
back up to the midpoint. WWV is recognizable by its pulsing tone (one second spacing)
and voice announcements each minute giving the "Universal Coordinated Time". If
necessary, look for it on bands C (10 MHz), D (15 MHz), and E (20 MHz). As soon as
you have identified WWV on one of these bands, make a small adjustment of C5 with a
miniature screwdriver or alignment tool. Then re-adjust the Tuning knob until you have
determined whether adjusting C5 moved WWV closer to or further away from the desired
point on the dial.
Repeat adjustment of C5 and the Main Tuning until the dial pointer is on the correct
frequency for WWV.
If you cannot find WWV on any of the three bands, try again at other times of the day.
One of these three frequencies (10, 15, or 20 MHz) should be loud and clear anywhere in
the continental USA at any time of day or night. 10 MHz is best for late afternoon and
evening.
Note to Hams or Experimenters
A very easy method for adjusting C5 is to listen for the VEC-102K's oscillator on a
nearby receiver or transceiver. Even with no antenna wire connected to the VEC-102K,
the oscillator is easily heard within a range of 10-15 feet.
Procedure:
1. Tune C1 to a specific frequency (e.g. 3.6 MHz, range A).
2. Tune other receiver to 3.6 MHz.
3. Listen to the VEC-102K and adjust Regeneration Control to the point where you
know that regeneration has just begun. (The receiver must be oscillating
(regenerating) for this method to work.)
4. Adjust trimmer C5 until you hear the oscillator signal. Adjust further for very lowest
audible tone (zero beat).
If you are using your own test signal from a signal generator or other RF source, simply
set the bandswitch and tuning dial to the test signal frequency and adjust C5 until you
hear the signal.