[Elecraft] S-Meter Sensitivity

[Don Brown]

Hi

Here are the readings I have on U2 =20

100 uV in

Pin 1  4.28v
pin 3  4.28v
pin 7  3.92
pin 6  3.92

0 uV in

Pin 1 3.96
pin 3 3.96
pin 7 3.92
pin 6 3.92

U2B is AC coupled so I would not expect to see a change in DC voltages. T=
his is a 150 khz signal

Hope this helps

Don Brown
KD5NDB
----- Original Message -----
From: k6se@juno.com
Sent: Wednesday, June 05, 2002 10:14 AM
To: DolfinDon@msn.com; elecraft@mailman.qth.net
Subject: Re: [Elecraft] S-Meter Sensitivity

K6SE wrote:

"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)."
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
My error here -- The AGC is deleloped on the control board and is fed
back to the IF amp at pin 5 of U12 on the RF board.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Don, KD5NDB wrote:

"Maybe a better piece of information is the actual AGC voltage at the
output of U2A with 50 and 100 uV in with the preamp on and off. I could
make this measurement if you think it would help."
----------
Please do.  It may be that my receiver gain is okay and the problem is in
the AGC circuitry instead.  Measurements at pins 1, 3, 6 and 7 of U2 on
the control board with 0 and 100 uV would be appreciated.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

"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 your choice."
----------
I'm not at all interested in setting my S-meter to one or the other of
the "standrards".  It's just that my K2's S-meter does not even closely
agree with the run-of-the-mill K2, and this tells me there's a problem
somewhere that I'd like to find and cure.

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


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