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Why no AGC for digital modes, as other modes?

 

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To Da Wiz; thank you, and a request, to make it better.
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Personally, I would appreciate the choice to use AGC, with my QMX+, or not, for all modes.
I have used fast or slow AGC with my FT-990 and TS-790A for years, for different modes,
and have found no noticeable performance penalty, except that the sound from no AGC
was harsh and undesirable, and the S meter unusable.
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Some folks will not RTFMs to turn off the AGC, or properly tweak other software or
hardware, and complain about imagined "bugs" - but for this ol' geezer,
the choice would be appreciated, and I promise I will not whine about the consequences ;-)
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Thanks for a hearing,
????????????????????????????????? DA Ol' Dog, wa4hei
 

By my understanding, DIGITAL mode is a "cheat." Note that is a SINGLE frequency mode -- thus works for FT8 <gasp>, WSPR, etc. that transmit a SINGLE frequency.?
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Thus, all you have to do is SHIFT the transmit frequency -- equivalent to a full modulation SSB SINGLE tone. Note that there is a FSK beacon mode (hiding in plain sight!).?
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So, you are just sending a CW signal -- full carrier, but just shifting the transmit frequency!
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> have found no noticeable performance penalty ....

Would second this request. Elegant solution of the "remove digimodes from mode switch to avoid ear damage" request 2 further up

Factory/default setting would be "off", + a brief mention in the manual.

"Da Wiz", hi. We really owe Hans a lot for his little gems.
 

For digi modes no agc helps.? Reason is that if a strong signal appears
in the pass band it pumps the agc and all signal are reduced by that
amount.? ?So a digi band has a couple of very strong signals it tends
too make the weak ones impossible to detect.? ?It was a big problem
with early receivers with a strong agc system rather than large
dynamic range.
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?described differntly AGC when it operated it does so by
making the radios gain lower to correct the excessive
level.? Good for the ears but it also is making the radio
less sensitive to accomplish that.
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--
Allison
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Post online only,?
direct email will go to the bit bucket.
 

Could have AGC (or just some crude clipping) on data to the DAC for the QMX headphone jack
Jerry
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On Thu, May 22, 2025 at 06:27 PM, ajparent1/kb1gmx wrote:

or digi modes no agc helps.? Reason is that if a strong signal appears
in the pass band it pumps the agc and all signal are reduced by that
amount.? ?So a digi band has a couple of very strong signals it tends
too make the weak ones impossible to detect.? ?It was a big problem
with early receivers with a strong agc system rather than large
dynamic range.
?
?described differntly AGC when it operated it does so by
making the radios gain lower to correct the excessive
level.? Good for the ears but it also is making the radio
less sensitive to accomplish that.
?
--
Allison
 

¿ªÔÆÌåÓý

? Re: Why no AGC for digital modes, as other modes?
From: ajparent1/kb1gmx
Date: Thu, 22 May 2025 21:27:50 EDT

My entire post that follows is from a self described obstinate and ancient analog rf weenie:

It was said: "So a digi band has a couple of very strong signals it tends too make the weak ones impossible to detect."
..."It was a big problem with early receivers with a strong agc system rather than large dynamic range." (that caused AGC pumping).

My immediate response is what is the minimum discernible signal difference between single tone cw with selectable AGC and
sequential single tone FT8 without? What is to be gained, without selectable AGC, by increased IMD and gain compression
with digital modes vs the use of AGC when operating cw?

I have read many a post, in other group postings, regarding what is, to me, apparent fantasy regarding FT8.

I? await my comeuppance, as a relative digital ignoramus.
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Though I differ, I thank you for your well stated and relevant reason regarding your apparent choice of no AGC for single tone modes.
Regarding my inquiry, it is far more relevant than "turn down the volume".

Given the relatively large dynamic range of my ancient FT-990 and TS-790A (and today's receivers? my QMX+?), and the?selectable
characteristics of AGC implementation, I have noticed no undesirable effects regarding the use of AGC that effected the receiver
?rf gain, whether I use cw or ft8/FT4 on hf, vhf, or uhf.

For my needs and desires, all I request is the ability to use AGC as I choose, complete with a more pleasant listening environment and an
AGC and S "meter" that works.

As far as I am concerned, the topic is closed.

Da Ol' Curmudgeon,
?????????????????????? ? ? ? ?? ??? wa4hei

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