[R-390] Call for measurements - 100dB carrier reading

[Graham Baxter]

Hi Dave

EAC R-390A SN 189

HP8640B generator, cable through terminated with 50 ohm load at
an HP 3400 rms meter. Short coax to balanced input, one side grounded.
DC Meter 10 Meg input resistance

100mV 99dB 11.18

10 mV  84dB 9.60V

1 mV  69 dB 7.41V

Voltage for 100dB = 11.20 ish but the meter reading  is very
compressed in this region

Graham
G8OAD

On 22/08/07, David Wise <David_Wise at phoenix.com> wrote:
> I'm working on a writeup of a mod I did to my R-390A
> a few years ago to improve the carrier zero adjust pot.
> It worked beautifully, but as I gathered data and did
> more experiments, I realized that it implicitly relies
> on a characteristic of my radio that seems at variance
> with the manual.  Before I send it to Perry Sandeen,
> I'd like to find out if it's worth the paper it's
> printed on.  If my radio's the only one it works on,
> there's no sense in putting it out.
>
> A while ago I asked for AGC measurements on an R-390.
> Now I'm looking for similar info on the R-390A.  Specifically:
>
> - Zero your carrier meter
> - Apply 1450KC to the balanced antenna input
> - Tune the radio to the signal, including antenna trim
> - Set the input amplitude to 100mV
> - Tell me the carrier meter reading
> - If you feel like it, measure the AGC with a VTVM
> - For extra credit, set the gen for 100dB carrier indication
>  and tell me the AGC voltage
>
> Be careful that you are actually putting in 100mV -
> the radio's impedance varies all over the place.
> I teed an RF voltmeter into the line.
>
> I hope I hear a lot of "Couldn't read it, it was pinned."
> Then I can pull off a great trick.  If not, then I can't
> get away with it and have to settle for merely good.
>
> Why 1450?  Because it's what I happened to use.  This
> week I'll try some other frequencies.
>
> Roger, you've seen thousands of these radios.  Do you
> think I have a chance?
>
> Thanks,
> Dave Wise
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