[R-390] R-390 Digest, Vol 180, Issue 14

[John]

There's a government document which tells how to design a frequency 
counter for the R-390.
https://www.r-390a.net/R390A-digital-frequency-readout-final.pdf

Basically you would have to read 3 or 4 different freqs, the 17 MHz 
crystal if below 8 MHz, the 11-34 MHz 2nd oscillator from the MC 
bandswitch, the 3.455-2.455 MHz signal from the KC VFO, and either the 
actual 455 kHz IF signal or the BFO freq. If you were to only read the 
3.455-2.455 MHz VFO freq and assume the other freqs were exact, you 
could be 3 or 4 kHz off, less accurate than the receiver dial.

To get the dial reading more accurate, build a 25 kHz calibrator, 
connect it to the antenna, and calibrate the dial at the 25 kHz marker 
closest to the station you are trying to measure.

Back in the dark ages, I built and sold the KRS brand of freq counter 
add-ons for short wave receivers.

John  KK6IL

On 4/13/2019 1:00 AM, jm wrote:

> Is there an easy way to connect the frequency meter in a point in which the
> oscillator signal could be found for all mhz positions?. What  would be the
> IF value  to offset ?
> I know that the challenge in this receiver is to obtain the maximun
> sensitivity and precision via calibration but that's not my league yet and
> meanwhile I think that a good solution is the frequency meter.