The Radio Information Board

I have one of these beasts that i have re-tuned for 2m amateur use. It recently started "drifting" on occasion when keyed. The receiver seems to stay on frequency, but the transmitter drifts. Only does it occasionally, not every time it is keyed. It is still transmitting at full power when it does this. For reference, when set to 146.520 simplex, it drifts between 146.518 and 146.526. If it "locks" when first keyed, it seems to stay locked, if it "unlocks" when first keyed, it seems to stay unlocked. I have checked the frequency of the reference oscillator, and it shows a constant 10.2399 MHz, even when it "unlocks". If I check the output of the VCO, at the input of the doubler, I see the variation there. I tried checking the control voltage to the VCO, but I can't seem to get consistant results. Maybe I am getting RF into my voltmeter (Ratshack) that is interfearing with my readings. Any thoughts on where to look further? I have the full service manual, compleate with board layouts and schematics, so feel free to give me part numbers and exact circuit locations to check!

It could be caused by the phase-lock-loop circuit oscillating. If so, it is a result of the VCO voltage being too low for the cicuit. This problem can be corrected by changing the values of 5 to 8 components, depending on the era of your radio. For whatever reason Regency/Wilson changed the components in the circuit to six different configurations over the life of that radio. None of them worked as well as the original.

To verify that the PLL circuitry is causing your problem look at the VCO test point with an oscilloscope set to AC. You should see a flat line during transmit. If there is high frequency noise any time that you key the radio then you will need to change the components to correct it.

Do you have a service manual?

Let me know if you get that far.

Bill