AGC Questions #sdrconsole


rmrrgs
 

Hello,

Would like to understand more re the AGC function in Console.

 

All sorts of combinations I could relate, but the following pretty much summarizes what is confusing  (to me at least).  It seems for me the results of changing the 

RF Gain, the IF Gain, and AGC On/Off are not consistent, or repeatable.

 

Using a RSPdx, and a simple horiz 70 foot long wire ant.

 

Last night was listening to WWV on 15 MHz.  Came in quite clear.

 

(a)         Baseline on Spectrum is -110 dbm  (good, right ?)

              AGC is Off.

              RF Gain at 0 (min)

 

(b)           I now turn the AGC On

                IF Gain is -55 dB

                Baseline jumps to -85 dbm  !

 

If I change the IF Gain to -35 dB, or -20 dB, no change

in Baseline or signal.

 

*So, why please does turning the AGC to ON apparently   

  increase the noise floor ?

 

*And, If I change the AGC now to OFF, nothing happens.

 Why ?  Shouldn’t it revert back to (a) again ?

 

BTW: would anyone, besides me, like to see Sliders,   

          rather than discretes, for the RF and IF 

          Gain settings ?

 

Best regards,

Bob

 


Simon Brown
 

Hi,

 

Sorry for the delay – I’ll provide an answer later today, bit busy atm.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of rmrrgs
Sent: 26 May 2020 12:25
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] AGC Questions #sdrconsole

 

Hello,

Would like to understand more re the AGC function in Console.

 

All sorts of combinations I could relate, but the following pretty much summarizes what is confusing  (to me at least).  It seems for me the results of changing the 

RF Gain, the IF Gain, and AGC On/Off are not consistent, or repeatable.

 

Using a RSPdx, and a simple horiz 70 foot long wire ant.

 

Last night was listening to WWV on 15 MHz.  Came in quite clear.

 

(a)         Baseline on Spectrum is -110 dbm  (good, right ?)

              AGC is Off.

              RF Gain at 0 (min)

 

(b)           I now turn the AGC On

                IF Gain is -55 dB

                Baseline jumps to -85 dbm  !

 

If I change the IF Gain to -35 dB, or -20 dB, no change

in Baseline or signal.

 

*So, why please does turning the AGC to ON apparently   

  increase the noise floor ?

 

*And, If I change the AGC now to OFF, nothing happens.

 Why ?  Shouldn’t it revert back to (a) again ?

 

BTW: would anyone, besides me, like to see Sliders,   

          rather than discretes, for the RF and IF 

          Gain settings ?

 

Best regards,

Bob

 


Russ Johnson
 

While on the topic of AGC, would you mind explaining the difference between the AGC control along the top (near ATT) and the one on the left side (under the mode/filter choices).

That has always confused me and a couple of users that I asked about it.

Thank you!


Simon Brown
 

Hi,

 

There’s AGC in the audio demodulation and probably AGC inside the radio firmware – which radio are you referring to?

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Russ Johnson
Sent: 27 May 2020 13:37
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] AGC Questions #sdrconsole

 

While on the topic of AGC, would you mind explaining the difference between the AGC control along the top (near ATT) and the one on the left side (under the mode/filter choices).

That has always confused me and a couple of users that I asked about it.

Thank you!


Russ Johnson
 

Hi..... I'm using the Airspy HF+