[Hallicrafters] SX-117 "S" Meter Readings?

[Bill Gerhold]

Ah yes, the AGC voltage.  You are correct, the common denominator here would
be the AGC voltage.  Why didn't I think of that?  I will try that test.
Thanks for the clue.

K2WH

-----Original Message-----
From: hallicrafters-bounces at mailman.qth.net
[mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Jim Brannigan
Sent: Sunday, May 22, 2005 10:38 AM
To: Bill Gerhold; 'hallicrafters-mailman.qth.net'
Subject: Re: [Hallicrafters] SX-117 "S" Meter Readings?

I am not familiar with the S-meter circuit of the SX-117, but most S-meters
respond, in some fashion, to AGC voltage.
With a high impedance voltmeter (over 50,000 ohms/volt), tune to a steady
carrier and measure the AGC voltage at different selectivity settings.
If the AGC voltage behaves as you described, the selectivity control is
affecting the IF gain.

Jim

> The selectivity control, which is connected to the 2nd conversion 50 kHz
IF
> section, is affecting the received (observed)
> "S" meter level.  That is, in the 5 kHz setting, I get a certain "S" meter
> indication, in the 2.5 kHz setting I get higher readings
> and in the .5 kHz setting, I get even higher "S" meter readings.  All on
the
> same signal.
>
> Looking at  the schematic, I do not see how narrowing the selectivity of
the
> receiver at the 2nd IF level would affect the "S"
> meter readings in the 1st IF section where the "S" meter is connected!
> While it matters little to me what the received signal
> strength is, I am left wondering why this would happen as I see no direct
> correlation between the 1st and 2nd IF operation that
> would affect the "S" meter.
>
> K2WH

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