Sensitivity and noise floor normalization

[K4RCG]

Running Argo side-by-side to FSKView using same soundcard source. Argo seems to produce 'crisper' images. Can FSKView sensitivity be inccreased?

[swharden]

Hey @K4RCG, can you include a screenshot that demonstrates this phenomenon? If you copy a screenshot (comparing Argo to FSKview) to the clipboard, you can paste it right in the comment box as you type a response in GitHub.

My suspicion is that Argo is configured to use a different contrast setting. FSKview allows the user to select the Argo colormap and to adjust brightness, but a contrast adjustment was intentionally omitted since increasing contrast is achieved by deleting data (turn contrast to 100% for an extreme example). That said, if a contrast adjustment would really be useful, I can try putting one in! Seeing the comparison would help get a better understanding for what makes Argo and FSKview different

[K4RCG]

Here it is...not a super example, but you get my drift.

[swharden]

Thanks for the screenshot! I cropped a region of Argo and cropped the same region of FSKview, then I stretched the FSKview screenshot vertically by 2x (to compensate for the "compress" option enabled in FSKview).

Argo	FSKview

automatic gain control: The largest difference between the two is what happens to the low-power signals when high-power WSPR transmissions begin. Both screenshots start off about the same, but once that strong WSPR transmission begins it really hurts the weak signals as seen in FSKview. This is probably because Argo is applying some type of frequency-windowed automatic gain control. I'll code something similar for FSKview and leave this issue open to track progress as I do. Thanks for providing this screenshot!

colormap note: The Turbo colormap is useful for some applications, but the Viridis colormap is probably the best for representing sensitivity to human eyes. If you want a slight extra advantages toward increased sensitivity, the Viridis colormap may give it to you!

[swharden]

@K4RCG actually I have one more idea... does your radio have AGC enabled? If so, turn it off, and your sensitivity with your existing software may stabalize!

[K4RCG]

Excellent analysis and explanation. And yes, I have AGC (Fast) enabled. I'll shut it off and see what happens. I always thought the WSJT decoder was not affected by AGC and left it enabled. Bob

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On Fri, Jul 3, 2020 at 8:49 PM Scott W Harden ***@***.***> wrote: @K4RCG <https://github.com/K4RCG> actually I have one more idea... does your radio have AGC enabled? If so, turn it off, and your sensitivity with your existing software may stabalize! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#15 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQEHCPLSIGSU5EQXT6LME6DRZY74RANCNFSM4OQBCQPQ> .

[swharden]

Excellent analysis and explanation. And yes, I have AGC (Fast) enabled. I'll shut it off and see what happens.

If you try another Argo vs FSKview comparison with AGC off, share the new screenshot here! I'm interested to see what this looks like too...

I always thought the WSJT decoder was not affected by AGC and left it enabled.

This may still be true, since WSPR relies entirely on frequency measurement (not amplitude measurement) so a flickering loud/quiet audio signal may not affect its ability to decode 🤔

[K4RCG]

Ugh; turned off AGC and signals really became distorted. Not worth the comparison. It was a mess! There was a W3 station relatively close to my QTH and his sig was not the cleanest; with AGC off, the spurs were horrible. I’ll try again in the future, but for now, AGC Fast back on. Bob

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On Fri, Jul 3, 2020 at 19:14 Scott W Harden ***@***.***> wrote: Excellent analysis and explanation. And yes, I have AGC (Fast) enabled. I'll shut it off and see what happens. If you try make another Argo vs FSKview comparison, share the new screenshot here! I'm interested to see what this looks like too... I always thought the WSJT decoder was not affected by AGC and left it enabled. This may still be true, since WSPR relies entirely on *frequency* measurement (not amplitude measurement) so a flickering loud/quiet audio signal may not affect its ability to decode 🤔 — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#15 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQEHCPOEADGCGFCD7OQD26DRZZQ45ANCNFSM4OQBCQPQ> .

[swharden]

I’ll try again in the future, but for now, AGC Fast back on.

Sounds good! Next time you try, glance at FSKview's level meter (the green bar on the top left) to ensure the audio isn't too loud. Often when disabling the AGC the volume jumps up. I look forward to seeing what it looks like when conditions quiet down on your side!

[K4RCG]

RRR I turned the RF gain down to reduce; just like the old days! People actually adjusted the RF gain!! Bob

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On Fri, Jul 3, 2020 at 19:58 Scott W Harden ***@***.***> wrote: I’ll try again in the future, but for now, AGC Fast back on. Sounds good! Next time you try, glance at FSKview's level meter (the green bar on the top left) to ensure the audio isn't too loud. Often when disabling the AGC the volume jumps up. I look forward to seeing what it looks like when conditions quiet down on your side! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#15 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQEHCPPQ4NI3ONAJOFXD3TDRZZWCLANCNFSM4OQBCQPQ> .

[K4RCG]

Screenshot with AGC OFF -- strong RTTY QRM present however.

[swharden]

I'll implement this in the Spectrogram library, and track progress over at swharden/Spectrogram#17