Talking about SSB telephony receivers...

The next problem that occurs is that many radios are loosely calibrated
with the selectable internal preamp OFF, a good idea for lower HF bands,
but questionable on VHF and above. The user manuals don't often state the
correct configuration for calibrated S meter response. Apparently, the
technology hasn't advanced enough to have the S meter calibrated whether
or not the internal preamp on in use.

(It is quite possible that the example that Harold gave is one of those
radios that is calibrated with internal preamp OFF and he measured it
with preamp ON.)
Owen

GM Owen

The transceiver I had back then didn't have a switcheable preamp. It was
just always on. Don't even remember the mfg, but it was a little flat radio.
3 inches high (if that) and spread all over the desktop. The "S" meter was
indeed driven from the limiters

Anyway, "S" meters that are inaccurate or change the value of the received
signal when you turn a preamp on or off (Or an attenuator on or off) are an
abomination. In this day and age of microprocessors, it's childs play to
adjust the "S" meter to accomodate those changes. (Take a look at the
"PicaStar" which does exactly that. It also yields 6 dB per "S" unit and 10
dB for every 10 dB over "S" 9 as well. Makes the radio into virtually a
piece of lab test equipment. Short of that use, the "S" meter report IS
rather rediculous. (You're 5-9, what was the call and name again?)

W4ZCB