[Elecraft] S-Meter Sensitivity

[Don Brown]

Hi

The S-meter sensitivity has nothing to do with the gain of the radio. The=
 S-meter reads the AGC voltage and displays it on the bar graph. The gain=
 and offset of the of the S-meter amplifiers is adjustable and that is wh=
at you are setting when calibrating the S-meter. If you want to set it fo=
r 50 uv or 100 uv at S9 with or without the preamp or any where else it i=
s up to you. As has been said in many posts the S-meter is quite subjecti=
ve and open to a lot of different interpretations. Even the major manufac=
turers can't agree on a standard. A lot of K2 builders have complained ab=
out the S-meter being stingy so I decided to make some measurements becau=
se I just happened to have 4 K2's in my lab. I posted the results of my t=
esting. Based on the measurements if you want to set the K2 up to read S9=
 at 50 uv the CAL S HI needs to be set 5 or 6 points lower than the manua=
l setting. Your K2 may be different but if you feel the S-meter is stingy=
 then setting CAL S HI a little lower will make it better. BTY I checked =
the S-meter calibrated at 50 uv and S9 and it is accurate and reads the s=
ame on all of the other bands. This surprised me. I don't think there is =
anything wrong with your K2. Set the S-meter to your liking. This is why =
the S-meter is not a very good indication of signal strength when giving =
reports.

Seems the S-meter is about as controversial as baluns and 450 ohm ladder =
line ;-)

Don Brown
KD5NDB

----- Original Message -----
From: k6se@juno.com
Sent: Tuesday, June 04, 2002 8:13 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] S-Meter Sensitivity

Well, after the discussion about S-meter sensitivity, I have to assume
that something is wrong with my K2.  The S-meter readings on my K2 appear
to be normal to me, but that's with the K2's preamp turned on.  When I
turn the preamp off (thereby losing 14 dB gain), the S-meter is very
stingy.

If I'm losing anything, I don't believe it's in the variable bandwidth
xtal filter because S-meter readings are the same in any mode whether I
use the K2's xtal filter or the KSB2's xtal filter (OPT1).  I don't
believe that the bandpass and low pass filters are the problem because
there's no problem with RF output during transmit.

That seems to leave only the mixer and post mixer amp as possible causes
of the problem.  The IF amp obviously is generating enough AGC to make
the S-meter seem ok with the preamp on, but I suppose the problem could
be there, too.  From the symptoms, it would appear that the 2nd xtal
filter and the product detector cannot be causing the lack of gain
problem.

Any ideas?

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