Pan display using FT8 - big sidebands on TX

K9RX
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Pan display using FT8 - big sidebands on TX

Postby K9RX » Sat Jul 22, 2017 3:53 pm

This is while using the 8000DLE on FT8, WSJT-X, VAC by Eugene.... not using PS

When I transmit I have the normal 0 db ALC value. The display shows the tone and the rest of the signal in the passband is maybe 70 - 100 db down where you see the normal 'ripples' .... but occasionally, as the tone is switching there's this odd "jump" for lack of a better way to describe it where the signal, on either side of the 'tone', will suddenly and only very briefly have these BIG shoulders on it that are only, its hard to capture but I'd say 35 - 45db down and broad - more than the 3Khz RX passband... and the waterfall is constantly white (this might be normal - not sure) ...

so this 'jump' ... is it REAL? Or is it something to do with how the display is being created.

I've got a call in to a friend to have him get on with me to see what he is receiving ... but i'm curious.

Gary
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w-u-2-o
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Re: Pan display using FT8 - big sidebands on TX

Postby w-u-2-o » Sat Jul 22, 2017 4:05 pm

"Jumps" in the panadapter during TX are usually indicative of a glitch (dropout, underrun, overrun) in the audio or Ethernet data streams.

I've seen this myself during WSJT-X and I have an otherwise very smooth running system that uses virtual audio for everything including phone, so it's not necessarily indicative of a problem with the PC or PowerSDR. The problem may actually be in how WSJT-X produces the audio stream.

It's funny, our software is so good we can now see every tiny little flaw in our signals. If you were running WSJT-X on a non-SDR radio you might have this issue and never even know or care! :)

One thing you can do, however, is to check the real-time audio performance of your setup. See this thread for more information on how to do that.

Another thing you can do is to make sure that you are "48KHz clean" across all of your virtual audio devices. You have changed the sample rates to 48KHz for all VAC devices in the Windows Sound Control panel, correct?

73,

Scott
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Re: Pan display using FT8 - big sidebands on TX

Postby w9mdb » Sat Jul 22, 2017 4:27 pm

I see the same thing on JT65.
I ran a 2nd copy of WSJT-X and used the output of the 1st as the input for the 2nd copy. On there you can see the multitones and I believe I can see some FFT shoulders in there too.
Seems the PowerSDR transmit FFT freq bin size is not adjustable. So all you see on the PowerSDR graph is a huge 200Hz hump for a 180Hz wide signal.
This probably works well for phone use or CW...but not multi-tone JT modes. Especially FT8 at 50Hz.

So the question is why isn't the transmit freq bin size adjustable like it is on the RX side?

de Mike W9MDB
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w-u-2-o
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Re: Pan display using FT8 - big sidebands on TX

Postby w-u-2-o » Sat Jul 22, 2017 4:35 pm

w9mdb wrote:I see the same thing on JT65.
So the question is why isn't the transmit freq bin size adjustable like it is on the RX side?

For the same reason the waterfall can't be independently scaled on TX--there are not enough volunteer developers interested in working on the user interface part of the code. In fact there is really only one right now who is interested in that (and we are lucky to have him!)

73,

Scott
K9RX
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Re: Pan display using FT8 - big sidebands on TX

Postby K9RX » Sun Jul 23, 2017 6:52 pm

Scott,

I have ... I need to go check ... ok - VAC1 is set to 2048 (buffer) and 48000 ... also not sure what it is but the buffer latency is set at 120mS.

Note when I open up the control panel for Eugene's (not remembering the last name) VAC program it shows this cable as using "192000"1 That is what I set the SR to in this program for both cables created, all 4 of them actually - minimum of 8K and max 192000 per the YT video by ... the 'G' station that does these things.

further someone suggested on the Yahoo forum in response to my post there to try "TUN" ... when I do that nothing changes - it looks... well GREAT. Indeed I do realize, which is why I asked the question, that this could just be how its 'shown' to me ... but of course the reason why I'm asking is to be sure its not real and being transmitted. The "Jump" is not 200Hz as someone wrote above - it is basically 'shoulders' that rise to about -35 or -40 and has a pretty low slope with the edges well past the ends of the 3Khz filter window displayed!

also - thanks for answering - as always.

Gary
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Re: Pan display using FT8 - big sidebands on TX

Postby K9RX » Sun Aug 27, 2017 1:25 pm

Since I started this topic I wanted to follow on that I believe all is well now. FT8 is working well as is JT65. I followed, I believe it was Simon, G7CNF's video that suggests you run less than 0 dbm. Sure enough I can see a noticeable drop in junk (IMD products) reducing the drive by just 1 db so that the ALC meter reads -1db.

Note - I wasn't aware of this until Scott, WU2O, posted a note to this effect that when you go to DIG modes (as selected by DIGU or DIGL in PSDR), that all audio processing is turned off ... I had created a TX Profile for DIG modes and had been using it but thought I would suggest either that one could 'assign' a TX Profile to DIGU (and one to DIGL as often the former is for most digital modes - the latter for RTTY which needs to have the dolly filters turned on) ... but that it would be easier if it just disabled the audio processing 'stuff' in the currently selected TX profile instead.

But I also knew if I left the SSB TX Profile on the output was once again with large IMD products and it took more power to get the same output... turns out after investigating that indeed every thing is turned off with the sole exception of the CFC settings. Both of those were/are left on! So unless/until that is fixed I would suggest you create your own TX profile for dig modes. I call it JT65 FT8 (of course it would apply to BPSK31/63 as well as all others using audio).

I will say I get a bit frustrated with FT8 as there is often, maybe 10% of the time, clearly 'good' signals there on the WJST spectrum display that don't get decoded. Haven't figured out why that is - if it is inherent to WSJT/FT8 (JT65 seems to be more reliable in this regard) or if it is something to do with delays, latency issues with PSDR/VAC as suggested by others. Still investigating. Would be interested if anyone has a follow on to this 'issue'.

I'm THOROUGHLY enjoying my Anan 8000DLE as well as PSDR. Learning more all the time - tweaking, excuse the language, the hell out of it making it MINE. And I have a list of what I believe would be improvements to the function/GUI that I'll submit in the near future - hopefully it will be received positively. I've designed UI's in the past for many products - industrial and consumer and think these are relevant and productive suggestions.

Gary
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Tony EI7BMB
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Re: Pan display using FT8 - big sidebands on TX

Postby Tony EI7BMB » Sun Aug 27, 2017 1:46 pm

Indeed Gary i saw that CFC was still enabled so like you I've created a profile just for DATA modes

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