[Elecraft] RF-Gain & S-Meter (again)

[Wes Stewart]

[putting on flame suit]  First all, as I've said several times, a modern radio with the "smarts" available today, shouldn't even need a manual "RF" gain control.

But, taking the K3 as an example, the "RF" gain control actually sums a DC voltage with the AGC voltage that is applied to an i-f amplifier stage.  Since the S-meter is effectively measuring the AGC voltage, it is entirely proper for the S-meter reading to increase as the "RF" gain is reduced.  This method, if used in moderation, opens the possibility of having the S-meter reading actually indicate the amplitude of the received signal.

The old time radios (I was using them in the 1950's) had a "real" RF gain control that actually did lower the RF stage(s) gain, usually by increasing the cathode bias.  This was totally independent of the AVC (as it was known then) system, thus the reduced RF gain lowered the AVC voltage, and the S-meter reading.  It also meant that the S-meter reading was totally useless for indicating the actual received signal amplitude.

Wes  N7WS

--- On Sat, 5/28/11, Bill Swindell - K1LED <bill.swindell at att.net> wrote:


> I have looked at several posts on
> this topic. I still feel that the S-meter
> is worthless if you turn down the RF hail at all. When U
> turn the RF gain
> down, the meter moves over to full scale. If the RF gain
> was truly reduced,
> I would think the S-meter indication would also go down. I
> guess they are
> emulating something that other radios do but, when U
> started in ham radio,
> many years ago, if I turned down the RF gain on the
> Hallicrafters SX101 that
> I was using, the s=meter wend down too.
> 
> I'm sorry but I like the old way and feel that it was more
> meaningful.