This is normal behavior for most modern receivers. The S-meter is reading
the AGC voltage, which will be a known function of the signal strength. So
when you want to tell someone their signal strength, you need to have the RF
gain up all the way. When you back the gain down, which causes the noise
and QRM between words not to be brought to the same volume as the signal,
you are reducing the amplifier gain by artificially applying some AGC
voltage. The S-mmeter will give a reading that reflects how strong a signal
would need to be in order for AGC to begin automatically changing the gain
again.
S-meter calibration is a whole 'nother subject. It will depend on which
preamps or attenuators you have switched in, what standard the manufacturer
defines to be S9 (sometimes 50 microvolts), and which definition of an
S-unit they choose to implement. Some organizations tried to define an
S-unit as a 6 dB change in signal level, but many manufacturers, including
Yaesu, use 3 dB per S unit as their standard.
Lloyd Rasmussen, Kensington, MD
http://lras.home.sprynet.com
-----Original Message-----
From: Kent Plemmons
Sent: Tuesday, February 11, 2014 10:20 PM
To: [log in to unmask]
Subject: RF gain/S meter relationship?
Hi All,
Warning, possible stupid question ahead!
I've noticed on my TS-590S that when I turn down the RF gain the s meter
value increases.
I often reduce RF gain when there is a lot of QRN in order to better hear
another station.
When I do that I also notice that the S value increases the more I reduce
the RF gain. If I leave the RF gain reduced, the S reading remains constant
even when different stations are transmitting at varying strengths.
I don't know how the S reading is determined but it seems like that if I
reduce the RF gain to the best level for hearing the other station that is
how the TS-590 determines the S reading. That doesn't sound like it is
correct but it sure seems to work that way.
Can anyone explain this to me?
Thank you all,
Kent, KK4FFF
Clyde NC
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