DAX RX Gain After Changing AGC for Digital Operation

Answers

• Ian1 Member ✭

  August 2015 edited May 2020

  I put mine on Fast and the slider full right in my testing this worked best for me. Ian

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• George KF2T Member ✭✭✭

  August 2015 edited December 2019

  For digi modes, I run with DIGU selected, AGC OFF, with slider at the "knee" (generally around 45-52, depending on Band), and then adjust the DAX channel level for the appropriate level in the digital Application (green Diamond lights in FLDIGI, 30 db in WSJT-x, 0 db in WSJT). Use a unique DAX channel per digital app. No need for DAX on SSB, unless you have a special situation?

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• Al K0VM Retired Member ✭✭

  August 2015 edited November 2017

  For digital modes like WSJT and PSK ( where there is more than one signal in the pass band)  I would like AGT threshold to be reached only on the strongest of signals. Therefore I leave the leave AGT on but set the slider down into the 20-30 range,  DAX is at default value and the WSJT-X signal level indicator indicates about 10 on RX noise.    To me it seems as if its best if the digital program does most of the leveling.   If AGC is run close to threshold, strong signals supress the weaker ones. 
  
  Just my way of doing it..
  
  AL, K0VM
  

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• W5XZ - dan Member ✭✭

  August 2015 edited June 2019

  That's curious, I see settings all over the ball park!  here, with WSJT-x, I run the rig a lot like i do on cw.  AGC-t ON, fast, < 50 typically...NB, sometimes...adjust DAX audio for '30' on the wsjt-x display..does WSJT-x have an agc function in its software? 
  
  must just be me, but on CW, when i turn off AGC, and start digging for weak signals,somebody comes along and blows my headphones off my head! digital decoding software doesn't overload, or clip, or go into gain compression, so it doesn't need AGC?
  
  would sure like to decode some more weak sigs, though, so will try the above suggestions.
  
  73, w5xz, dan

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• Ron Schwartz Member

  August 2015 edited March 2017

  Actually, George has a point.  When I started this posting I just assumed that I should be setting the RX Gain in the DAX control panel back to a 'normal' level when I went back to voice mode.  Since voice modes do not use DAX, I really should not worry about the DAX setting when running voice.

  It is interesting that there is no consensus yet on how to set AGC for digital, so I was not missing something.  I would be interested in Flex's opinion on the 'best practice'.

  Ron
  

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• W5XZ - dan Member ✭✭

  August 2015 edited June 2019

  well, my settings can't be THAT bad...i did pull vp8alj, falklands, out of the mud on a noisy 160m band, with modest antennas...twice, now...full credit, though, to my HiZ 4sq, on receive..
  
  'just sayin', as the kids say?
  
  73, w5xz, dan
  
  

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• Tim - W4TME Administrator, FlexRadio Employee admin

  August 2015 edited December 2016

  So here is my answer, not necessarily the FlexRadio answer.
  
  It depends on two factors; the receive bandwidth filter and band QRN / QSB conditions.  It really helps to understand how AGC algorithm is implemented in the radio since it is a dual track AGC that works on both fast and slow increases in gain.  I highly recommend reading the section on Noise Mitigation in the SmartSDR for Windows Software User's Guide.
  
  In general, I do not want a stronger signal in my receive passband "capturing" the AGC where the audio gain will decrease, making weak signal reception more difficult.  If I am using a narrow filter relative to the mode I am operating and the bandwidth of that filter is such that the probability of another strong signal entering the passband is low, then I use the Fast or Medium AGC and adjust the AGC-T to the point where I have maximum signal to noise (SNR) based on band conditions (see the section in the manual on how to do this).
  
  If band conditions are fluctuating or I am using a wide RX filter, then I set the AGC to Slow or sometimes Off.  Again if the AGC is set to Slow, I adjust the AGC-T for maximum SNR.  If I use the Off setting, you have to be a little more careful.  When AGC is off,  it really isn't off.  It means that a fixed amount of gain will be applied to both fast and slow increases in noise.  I use these setting so that a strong signal in my passband does not capture the AGC and trigger an AF gain reduction.

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• George KF2T Member ✭✭✭

  August 2015 edited May 2019

  As the Good Book says, there's more than one way to skin a cat. Or, your mileage may vary. If it works well in your unique Installation, it's good enough. Tweak on!

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• NX6D Dave Member ✭✭

  August 2015 edited December 2016

  I'm with George on this one.  I set AGC to OFF and set the AGC-T control to about 30, which is approximately the knee when my 6500 is in SSB mode.  The only reason I choose 30 is that it is my conventional number.
  
  After that, I adjust the DAX audio level with the DAX control panel.  Most of the time I have plenty of adjustment room, and I can always change AGC-T up or down as needed.
  

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• Jay Nation Member

  August 2015 edited August 2016

  My mileage varies from session to session. The settings get adapted for whatever tweak I'm using with that session. I use whatever works, heavy on the "whatever", and it usually works. I used to believe, I'd find some sort of magic sweetspot setting. Then I remembered I don't believe in magic.
  
  73, Jay - NO5J  

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• mdavid01 Member

  September 2015 edited May 2019

  
  For psk 31 I use AGC off, slider set to 45 or so, usually i adjust agc based on waterfall in fldigi.
  Fldigi I have viewer squelch set to 1.5 with Receive Squelch level set 1/4 from bottom
  
  I found today that while working Feld **** that I needed to crank the agc slider to 90 or so to make out the information

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• Jay Nation Member

  September 2015 edited August 2016

  "Today" I'm  running preamp off, agc off, threshold 16%, and DAX RX 70%, 4k passband, with WSJT-X 1.6.0 -r5881. 
  Works as I expect it too.
  
  73, Jay - NO5J

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