[Elecraft] S-Meter Sensitivity

[Don Brown]

Hi

Yes you are correct, but the S-meter reading of the AGC voltage is modifi=
ed in gain and offset in software by the MPU. Maybe a better piece of inf=
ormation is the actual AGC voltage at the output of U2A with 50 and 100 u=
V in with the preamp on and off. I could make this measurement if you thi=
nk it would help. If the readings are about the same as your K2 then you =
may just need to adjust the S-meter gain to get S9 at 100 uV or 50 uv you=
r choice.

Don Brown

----- Original Message -----
From: k6se@juno.com
Sent: Wednesday, June 05, 2002 4:24 AM
To: DolfinDon@msn.com; elecraft@mailman.qth.net
Subject: Re: [Elecraft] S-Meter Sensitivity

Don, KD5NDB wrote:

"The S-meter sensitivity has nothing to do with the gain of the radio."
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
I believe any bozo realizes that.

BUT, the gain of the radio DOES affect the S-meter reading.

If ARRL says that it takes only 19 uV into the K2  with its preamp on to
make the meter read S9 (and 115 uV with the preamp off), and you tested
those four K2's with the preamp turned OFF which looks like they might be
close to the K2 that ARRL tested.

I estimate that my K2 requires about 100 uV to read S9 with the preamp
ON, so the logical conclusion is that there's a loss of about 14 or 15 dB
of gain in the receive chain somewhere before the IF amplifier U12 (where
the AGC voltage which drives the S-meter is developed).

73, de Earl, K6SE
67 countries with K2 #2622 and counting.....


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