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RF-Gain & S-Meter (again)

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Bill Swindell - K1LED

RF-Gain & S-Meter (again)

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.

n7ws

Re: RF-Gain & S-Meter (again)

[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 <[hidden email]> 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.

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Don Wilhelm-4

Re: RF-Gain & S-Meter (again)

In reply to this post by Bill Swindell - K1LED

Bill,

The Hallicrafter SX101 was one of the few exceptions. Most receivers
behaved similar to the way the K3 does when the RF gain is reduced - the
S-meter goes up. With the SX101 (if I recall correctly), the S-meter
reading for all signals was reduced when the RF Gain was reduced.

If I may, can I present a "different way of looking at it" - if the
no-signal S-meter reading (with the RF gain reduced) is S-4, then
signals below S-4 will result in no additional S-meter deflection. A
signal that is S-5 will still flick the S-meter up to S-5, and you can
report him as S-5.

You likely turned the RF gain down so the atmospheric noise would not be
bothersome - if you go beyond that point, you will be reducing signals
that can be copied above the noise level.

What is really happening is that you are reducing the RF gain to reduce
the amount of atmospheric noise that you must listen to on any one
band. When you can just barely hear that noise, the S-meter will read
at the level of that band noise. Signals at a level above that will
still indicate at their proper S-meter readings.

At least that is how it works on my K3 with the S-meter set to ABS
mode. I think this way is meaningful.
Right now, I am listening to I2VRN on 7.102 kHz and his S-meter
deflection does not change when I reduce the RF gain from full to about
the 2:30 o'clock position (he is S-8 here), but tuning away to a quiet
spot on the band, I see the minimum S-meter reading is S-3. I would
give him an S-8 report.

Try it and see - only the lower end of the S-meter scale becomes
unusable, but the actual signals that you hear are indicated at their
proper level - assuming one has calibrated the S-meter for S-9 with a 50
uV signal.

73,
Don W3FPR

On 5/28/2011 8:11 PM, Bill Swindell - K1LED 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.
>

Bill Swindell - K1LED

Re: RF-Gain & S-Meter (again)

I think it's weird. I still think the way is should work is to actually reduce the rf-gain. I think the purpose of the rf-gain would be to limit the input to the rf input of the receiver to prevent overloading. Oh well, that;s the way it is.

Grant Youngman

Re: RF-Gain & S-Meter (again)

An attenuator does that.

Sent from my iPhone

On May 28, 2011, at 8:41 PM, Bill Swindell - K1LED <[hidden email]> wrote:

> I think it's weird. I still think the way is should work is to actually
> reduce the rf-gain. I think the purpose of the rf-gain would be to limit the
> input to the rf input of the receiver to prevent overloading. Oh well,
> that;s the way it is.
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/RF-Gain-S-Meter-again-tp6415527p6415650.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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AC7AC

Re: RF-Gain & S-Meter (again)

In reply to this post by Bill Swindell - K1LED

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Phil Kane-2

Re: RF-Gain & S-Meter (again)

On 5/28/2011 8:08 PM, Ron D'Eau Claire wrote:

> I hope this clears up the confusion a bit Bill. It sounds like you have an
> unusual receiver in that SX-101. Bill Halligan was famous for innovative
> ideas in his receivers, but the way he handled the S-meter response to the
> RF gain control was one specific to that receiver, not the general rule.

I had an SX-101 from 1961 through 1974. IIRC it was a separate
"chain" that was not affected by the AGC/RF gain setting that
produced the voltage that drove the S-meter.

-- 73 de K2ASP - Phil Kane
Elecraft K2/100 s/n 5402

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