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RF-Gain & S-Meter (again)

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Mike Morrow-3

RF-Gain & S-Meter (again)

Ron wrote:

> It sounds like you have an unusual receiver in that SX-101...the
> S-meter response to the RF gain control was one specific to that
> receiver, not the general rule.

Phil wrote:

> 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.

In some sense, there *are* two gain control systems in the SX-101
for the RF and IF stages. Stage gain is reduced by:
(1) AGC, which as it gets larger for stronger signals increases bias
voltage to the RF and IF stages. This is the input to the S-meter.
PLUS
(2) Manual RF gain, which manually increases the resistance in the
cathode circuits of the RF and IF stages to reduce stage gain,
independent of AGC bias voltage.

The more common method for the past 65 years or so has been to use the AGC
circuit to reduce stage gain for both automatic AND manual gain control:
(1A) AGC, which as it gets larger for stronger signals increases bias
voltage to the RF and IF stages. This is the input to the S-meter.
PLUS
(1B) Manual RF gain, which manually increases the bias voltage in the
AGC circuit to the RF and IF stages, and thus directly affects
the S-meter just as any AGC bias voltage increase would.

Mike / KK5F
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Guy, K2AV

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

Exactly, which is what most people expect, without knowing that they
expect it, since 99% of ham receivers have done that since AGC first
showed up.

This behavior is CODED INTO the K3 firmware algorithm for the S-meter
presentation. It is not mandated by the way hardware is wired. It is
a choice made by the coder of K3 firmware, not the designer of circuit
board traces. The firmware COULD be coded to always show the signal
level at the antenna input regardless of RF gain setting, which is
what I would prefer. This could be turned on when CONFIG:SMTR MD is
set to ABS.

73, Guy.

On Sat, May 28, 2011 at 11:04 PM, Mike Morrow <[hidden email]> wrote:
> The more common method for the past 65 years or so has been to use the AGC
> circuit to reduce stage gain for both automatic AND manual gain control:
> (1A) AGC, which as it gets larger for stronger signals increases bias
> voltage to the RF and IF stages. This is the input to the S-meter.
> PLUS
> (1B) Manual RF gain, which manually increases the bias voltage in the
> AGC circuit to the RF and IF stages, and thus directly affects
> the S-meter just as any AGC bias voltage increase would.
>
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Deni F5VJC

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

I fully agree with Guy.

I wish the S meter would be changed to indicate true S level even with
RF gain turned down (as is usual if you're operating the RX
correctly).
What is the point of sticking with the 'OLD WAY' just because it's
always been that way.
This is an Elecraft K3 after all.

Elecraft, If it's really possible please do consider this change.

73, Deni
F5VJC

On 29 May 2011 21:33, Guy Olinger K2AV <[hidden email]> wrote:

> Exactly, which is what most people expect, without knowing that they
> expect it, since 99% of ham receivers have done that since AGC first
> showed up.
>
> This behavior is CODED INTO the K3 firmware algorithm for the S-meter
> presentation. It is not mandated by the way hardware is wired. It is
> a choice made by the coder of K3 firmware, not the designer of circuit
> board traces. The firmware COULD be coded to always show the signal
> level at the antenna input regardless of RF gain setting, which is
> what I would prefer. This could be turned on when CONFIG:SMTR MD is
> set to ABS.
>
> 73, Guy.
>
> On Sat, May 28, 2011 at 11:04 PM, Mike Morrow <[hidden email]> wrote:
>> The more common method for the past 65 years or so has been to use the AGC
>> circuit to reduce stage gain for both automatic AND manual gain control:
>> (1A) AGC, which as it gets larger for stronger signals increases bias
>> voltage to the RF and IF stages. This is the input to the S-meter.
>> PLUS
>> (1B) Manual RF gain, which manually increases the bias voltage in the
>> AGC circuit to the RF and IF stages, and thus directly affects
>> the S-meter just as any AGC bias voltage increase would.
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

--
73 Deni,

F5VJC
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K5DNL

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

In reply to this post by Guy, K2AV

Hello all,

I agree with Guy.

This could be turned on when CONFIG:SMTR MD is
set to ABS.

Ken K5DNL
------------------------------------------------------------

--- On Sun, 5/29/11, Guy Olinger K2AV <[hidden email]> wrote:

> From: Guy Olinger K2AV <[hidden email]>
> Subject: Re: [Elecraft] RF-Gain & S-Meter (again)
> To: "Mike Morrow" <[hidden email]>
> Cc: [hidden email]
> Date: Sunday, May 29, 2011, 2:33 PM
> Exactly, which is what most people
> expect, without knowing that they
> expect it, since 99% of ham receivers have done that since
> AGC first
> showed up.
>
> This behavior is CODED INTO the K3 firmware algorithm for
> the S-meter
> presentation. It is not mandated by the way hardware
> is wired. It is
> a choice made by the coder of K3 firmware, not the designer
> of circuit
> board traces. The firmware COULD be coded to always
> show the signal
> level at the antenna input regardless of RF gain setting,
> which is
> what I would prefer. This could be turned on when
> CONFIG:SMTR MD is
> set to ABS.
>
> 73, Guy.
>
> On Sat, May 28, 2011 at 11:04 PM, Mike Morrow <[hidden email]>
> wrote:
> > The more common method for the past 65 years or so has
> been to use the AGC
> > circuit to reduce stage gain for both automatic AND
> manual gain control:
> > (1A) AGC, which as it gets larger for stronger signals
> increases bias
> > voltage to the RF and IF stages. This is the
> input to the S-meter.
> > PLUS
> > (1B) Manual RF gain, which manually increases the bias
> voltage in the
> > AGC circuit to the RF and IF stages, and thus
> directly affects
> > the S-meter just as any AGC bias voltage
> increase would.
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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ab2tc

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

In reply to this post by Deni F5VJC

Hi,

I support the wish for this as an option also. But if we could get the AGC threshold adjustable up another 6dB or so I for my part would have no need for it.

AB2TC - Knut

Deni F5VJC wrote

I fully agree with Guy.

I wish the S meter would be changed to indicate true S level even with
RF gain turned down (as is usual if you're operating the RX
correctly).
What is the point of sticking with the 'OLD WAY' just because it's
always been that way.
This is an Elecraft K3 after all.

Elecraft, If it's really possible please do consider this change.

73, Deni
F5VJC

Snip>

AC7AC

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

In reply to this post by Deni F5VJC

CONTENTS DELETED

The author has deleted this message.

aandrei

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

In reply to this post by K5DNL

I agree with Guy and Ken.

Adi
2E0TTX

On 29/05/2011 23:05, Ken Roberson wrote:

> Hello all,
>
> I agree with Guy.
>
> This could be turned on when CONFIG:SMTR MD is
> set to ABS.
>
> Ken K5DNL
> ------------------------------------------------------------
>
> --- On Sun, 5/29/11, Guy Olinger K2AV<[hidden email]> wrote:
>
>> From: Guy Olinger K2AV<[hidden email]>
>> Subject: Re: [Elecraft] RF-Gain& S-Meter (again)
>> To: "Mike Morrow"<[hidden email]>
>> Cc: [hidden email]
>> Date: Sunday, May 29, 2011, 2:33 PM
>> Exactly, which is what most people
>> expect, without knowing that they
>> expect it, since 99% of ham receivers have done that since
>> AGC first
>> showed up.
>>
>> This behavior is CODED INTO the K3 firmware algorithm for
>> the S-meter
>> presentation. It is not mandated by the way hardware
>> is wired. It is
>> a choice made by the coder of K3 firmware, not the designer
>> of circuit
>> board traces. The firmware COULD be coded to always
>> show the signal
>> level at the antenna input regardless of RF gain setting,
>> which is
>> what I would prefer. This could be turned on when
>> CONFIG:SMTR MD is
>> set to ABS.
>>
>> 73, Guy.
>>
>> On Sat, May 28, 2011 at 11:04 PM, Mike Morrow<[hidden email]>
>> wrote:
>>> The more common method for the past 65 years or so has
>> been to use the AGC
>>> circuit to reduce stage gain for both automatic AND
>> manual gain control:
>>> (1A) AGC, which as it gets larger for stronger signals
>> increases bias
>>> voltage to the RF and IF stages. This is the
>> input to the S-meter.
>>> PLUS
>>> (1B) Manual RF gain, which manually increases the bias
>> voltage in the
>>> AGC circuit to the RF and IF stages, and thus
>> directly affects
>>> the S-meter just as any AGC bias voltage
>> increase would.
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Craig Smith

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

In reply to this post by AC7AC

AMEN, Ron. Since I got the P3 I don't think I've ever looked at the S meter
on the K3.

73 Craig AC0DS

<> Those who have a P3 already have that antenna input signal strength
reading,
<> in dBm or S-units right on the display - independent of gain controls,
attn,
<> preamp, etc.

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