How to limit max gain

wa2cop
Posts: 27
Joined: Mon Dec 20, 2021 9:17 pm

How to limit max gain

Postby wa2cop » Thu Jan 13, 2022 9:19 pm

I would like to know if there is a way to limit the maximum gain applied to the AGC minimize clipping on the input of my Audio Device on overly strong signals. I am constantly adjusting the volume (ie RX AF Gain ).

Any suggestions?
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kc2rgw
Posts: 165
Joined: Mon Jun 22, 2020 5:44 pm

Re: How to limit max gain

Postby kc2rgw » Fri Jan 14, 2022 12:28 pm

Try using the headphone jack as your output if you aren't already. Sounds like a mismatch on drive level to the input of whatever your audio output device is.
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w-u-2-o
Posts: 5540
Joined: Fri Mar 10, 2017 1:47 pm

Re: How to limit max gain

Postby w-u-2-o » Fri Jan 14, 2022 1:06 pm

This would appear to be two separate problems.

1) as @kc2rgw pointed out, you should never be experiencing clipping at the input of your audio device. That means the audio level out of the radio is set too high. Use the Master AF or RX1 (or RX2) AF controls to set the maximum allowable output level if you are using a hardware output on the radio. If you are using VAC this should never be a problem even if all controls are set to 100%. Set your AGC gain to a very high value and find a large signal, then make this adjustment.

2) if you are constantly adjusting the volume between small signals and large signals, that is a function of your AGC gain. The higher this setting the less audio output dynamic range you will experience. Under no circumstances will a high setting affect the maximum audio output level, which you have already set per (1) above. Note that when AGC gain is high this tends to allow the noise floor to be heard more clearly.

Once a proper audio drive level is set per (1) above, and once a comfortable listening level is obtained by adjusting your audio device volume knob, then what you really want to do is ride the AGC gain control as discussed in (2) in order to obtain the most intelligible/comfortable/pleasing audio on a signal by signal basis. If you don't mind the noise, or if you are forced to copy both large and small signals as part of a given QSO, you can simply leave the AGC Gain at a very high value.

To further reduce noise, consider also optimizing your RF dynamic range by increasing the step attenuator until you see a drop in signal-to-noise ratio amongst the largest signals on the panadapter, then back up a few dB. Also consider using NR2 noise reduction mode.
wa2cop
Posts: 27
Joined: Mon Dec 20, 2021 9:17 pm

Re: How to limit max gain

Postby wa2cop » Fri Jan 14, 2022 3:56 pm

ok you both gave me a ton to think about - I will adjust accordingly and report back.

thanks as always for the support!

w-u-2-o wrote:This would appear to be two separate problems.

1) as @kc2rgw pointed out, you should never be experiencing clipping at the input of your audio device. That means the audio level out of the radio is set too high. Use the Master AF or RX1 (or RX2) AF controls to set the maximum allowable output level if you are using a hardware output on the radio. If you are using VAC this should never be a problem even if all controls are set to 100%. Set your AGC gain to a very high value and find a large signal, then make this adjustment.

2) if you are constantly adjusting the volume between small signals and large signals, that is a function of your AGC gain. The higher this setting the less audio output dynamic range you will experience. Under no circumstances will a high setting affect the maximum audio output level, which you have already set per (1) above. Note that when AGC gain is high this tends to allow the noise floor to be heard more clearly.

Once a proper audio drive level is set per (1) above, and once a comfortable listening level is obtained by adjusting your audio device volume knob, then what you really want to do is ride the AGC gain control as discussed in (2) in order to obtain the most intelligible/comfortable/pleasing audio on a signal by signal basis. If you don't mind the noise, or if you are forced to copy both large and small signals as part of a given QSO, you can simply leave the AGC Gain at a very high value.

To further reduce noise, consider also optimizing your RF dynamic range by increasing the step attenuator until you see a drop in signal-to-noise ratio amongst the largest signals on the panadapter, then back up a few dB. Also consider using NR2 noise reduction mode.
wa2cop
Posts: 27
Joined: Mon Dec 20, 2021 9:17 pm

Re: How to limit max gain

Postby wa2cop » Fri Jan 14, 2022 8:10 pm

ok I found the issue - I had EQ set in VoiceMeter Banana which was driving up the gain above zero. All is good. I have also made some of the changes you suggested and am able to control via the AGC vs everything else. Thanks again!

You may want to move this to VAC section.

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