AGC-T persistence by band and antenna settings

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  • Updated 3 years ago
Its been a while since I heard any thing about this. New slices still start with high gain and I still need to adjust AGC-T when changing antennas. Where are things going with this?
Andrew VK5CV
F6500 SSDR 1.6.17 Win10.
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Andrew Russell

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Posted 3 years ago

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Tim - W4TME, Customer Experience Manager

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Changing the RX antenna does not change the AGC-T value. Creating a new slice in the same panadapter using the new slice or clone method, inherits the ACG-T value of the nearest slice.

So I am not sure what you are asking for. You will need to explain what you mean in more detail.
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Andrew Russell

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Tim,
The main issue is switching the RX antenna between a transmitting antenna on Ant 1 and or Ant 2 and the Pixel loop on RXA. So I have 3 potential Rx antennas with very different signal and noise inputs to the SCU and very different optimal AGC-T settings needed as I switch back and forth. Each time I need to readjust and remember the exact number set before.
A new slice usually starts too high but this is only OK if the loop is selected with my high noise level on the low bands.
Andrew
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Barry N1EU

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It sounds like he wants SSDR to remember your AGC-T setting you used the last time you were on the same band and ideally the last time you were on the same band/antenna combination.

73, Barry N1EU
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Tim - W4TME, Customer Experience Manager

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OK.  But since the AGC-T is a very dynamic control that really needs to be adjusted for band specific conditions; making it persistent could lead to a degraded SNR.  Even operating on the same band during the times of day when a band opens or closes should trigger a readjustment of the AGC-T.

The AGC-T should be the first thing you always adjust when changing to a different band.  it is very easy to adjust the AGC-T to find the AGC "knee" which optimizes the SNR.  This is especially true if you have to use any of the DSP noise mitigation features (NB or NR), as they are more efficient if the AGC-T is set properly first.

This is why we implement a best approximation on a per band basis as a starting point so that you do not accidentally leave it set to either one of the max or min extremes resulting in non-optimal reception.
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Barry N1EU

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Thanks Tim!  Could you please just say a bit on how the approximation on a per band basis is done?  Is that just a lookup table of static values from the factory, is it based on the individual user's settings in the past,  or is the rx actually sampled etc???
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Tim - W4TME, Customer Experience Manager

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We approximated the AGC-T initial settings based on an urban / rural noise floor estimates for the different ham bands. they were determined based on user test data finding optimal AGC-T settings by band.  The higher the frequency, the quieter the band, the greater the initial AGC-T value. They are hard coded into the band selection logic.
(Edited)
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Al / NN4ZZ

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This is also a good plug for the idea to "automate the AGC-T" setting.  Currently this request is the #2 idea on the list with 42 votes.   More info here:

https://community.flexradio.com/flexradio/topics/option-to-automate-the-agc-t-setting

The idea would add an option to automate the setting or continue to manually set it.  In the automated mode it would account for changing antennas, and rotating a directional antenna as well as the noise floor that varies by time of day and band. 


Mockup of new feature and controls....



Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com