Native PSK mode?

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  • Updated 3 years ago
While using my 6700 with DM780 on PSK31, I noticed that the waterfall on SSDR appeared "cleaner" than the waterfall in DM780. I am using DAX for the audio input to DM780. Would PSK reception be any better, particularly with weaker signals if the decoding were done closer to the antenna inside the Flex? I assume that could be done withe the Waveform API, and is anyone working on that?
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Mark Erbaugh

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Posted 3 years ago

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Jay / NO5J

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Mark
Sorry for this analogy,  But that's kind of like asking would I be better looking in a photo taken with a better camera? The picture might look better. But would it make me look any better?
SmartSDR has the better camera.

Remember that there are windows audio drivers in between SmartSDR and DM780, because DM780 requires them. check for sample rate conversions, try to get every rate set to 48000. WDM-KS has the lowest latency but it may not work the cleanest.

Yeah if SmartSDR could decode PSK31 itself, it might be capable of doing a better job, and wouldn't need a 3rd party waterfall. But then again If DM780 was a radio It would probably cost a lot more.  
73, Jay - NO5J
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George Molnar, KF2T, Elmer

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Mark, are you suggesting a Waveform that will decode (insert digital mode here) and pass it to a virtual serial port (or IP stream) for display on a terminal program? Sounds like a cool idea, but probably a ways off since it would be a Flex-only effort at this point. 

Would be a nice way to get rid of those pesky Windows drivers, sample rate conversions, and "stuff." My Mac would like that. Probably would work a little better, too.

That said, Jay has a point. The SSDR waterfall is going to look the best since it's "closest" to the source and has been lovingly designed to look awesome.
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Alex - DH2ID, Elmer

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Mark, I my screenshots show DM780 and SmartSDR. Ok, I grant you that the SSDR
waterfall looks cleaner, but D780 only shows up to 3800 Hz bandwidth for the whole
screen and that does show everything in that restricted area.

Jay, please correct me if i a mistaken but where does WDM-KS come in here?
I know this driver from my Flex-3000, but here the audio stream surely goes straight
from DAX to DM780?



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Jay / NO5J

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Alex
Your right, WDM-KS probably isn't even a factor. One of those holes in my understanding of the Windows Audio interface. This just made me recall issues, I used to have occasionally with PowerSDR and VAC, DAX is Not VAC. Thankfully! 
73, Jay - NO5J
(Edited)
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Alex - DH2ID, Elmer

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My pleasure, Jay. 73, Alex DH2ID
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Mark Erbaugh

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Here is what I'm thinking. The digital modes are typically first demodulated as a SSB signal to audio. Then the audio is digitized and analyzed. Of course, with DAX the signal is already digitized.

Would it be possible to directly demodulate the PSK stream from the I and Q data. I seem to recall an article that said with I and Q any modulation can be demdulated. I assume that each time there is a conversion step, noise is introduced that degrades ultimate reception. By eliminating conversion steps and moving the demodulation close to the antenna, I would think the ability to copy a signal would be improved, but would that improvement be noticeable?