Ron, AC7AC wrote:

"Someone I was chatting with recently said he had tested the S-meters of
several receivers and found that 1 S-unit can equal anything from 3 dB to
more than 6 dB. I had always assumed the target was 6 dB/S-unit. 
Apparently not so."
==========

Years ago, there were two "standards" for S-meters.

1) The Collins standard was 100 uV = S9 and each S-unit was 8 dB.

2) The Hallicrafters standard was 50 uV = S9 and each S-unit was 6 dB.

Manufacturers naturally adopted the Hallicrafters standard because the
Collins standard resulted in a stingier S-meter (higher S-meter readings
= better receiver, right? - No!!!!)

It is rare, with the new transceivers currently on the market to find one
that strictly adheres to the "standard".  Virtually every tranceiver
today uses the 50 uV = S9 criterion, but the change per S-unit is much
less than 6 dB.  This results in a substantial signal such as 1 uV (which
should read S3.5 on an accurate S-meter).not even budging the S-meter on
most receivers today.

In dB above S9, the S-meters most transceivers today seem to be fairly
accurate.

If all manufacturers complied with the "standard" to the letter, S-meter
readings would be more meaningful.  As it is now, they are useful only
for reference readings such as when someone does an A/B check on his
antennas with you.

BTW, the values I posted originally were with the receiver preamp turned
off in all cases.

73, de Earl, K6SE
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