Vectronics VEC-1012K User Manual
Page 19
VEC-1012K Owner’s Manual
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red (+) voltmeter lead to pin #17. Using a small screwdriver, adjust L5 for a
reading of 2.3 volts. No further adjustment will be required.
Final Alignment--Oscillator Coil L4:
If possible, your kit should be mounted in its VEC-1012KC metal cabinet (or
other enclosure) before adjusting L4. The tuning oscillator frequency coverage
may change slightly if you align L4 with the pc board out of the box, then install
it later. There are several ways to calibrate L4 for coverage. Choose the method
most compatible with the tools you have available:
Option 1: Calibrating with a Signal Generator or FM-Service Monitor.
Set the generator up as follows:
!
Frequency:..............................154.0 MHz
!
Output Level: .........................10 uV (-90 dBm)
!
Modulation: ............................1 kHz tone at 5 kHz FM deviation
Connect the generator output to your kit's antenna jack using a 50-ohm patch
cable. Plug in headphones or external speaker to monitor generator signal.
1. Set TUNE to 154.0 MHz (fully counterclockwise).
2. Set SQUELCH open (fully counter-clockwise).
3. Power the radio and set VOLUME for a comfortable level.
4. Slowly tune L4 back and forth with the insulated tuning tool to locate the 154
MHz test signal.
Your receiver's varactor tuning circuit should now cover approximately 4 MHz
from bottom to top, providing coverage from 154 to 158 MHz. You may alter
the tuning range, if you wish, to cover any 4 MHz segment from 150-154 to 158-
162 MHz by readjusting L4 accordingly.
Option 2: Calibrating with a Frequency Counter.
Your kit's NBFM receiver IC features a buffered test point for measuring
oscillator frequency with a digital counter. Locate this point on the diagram
below: