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WXtoimg Decoding

Posted: Tue Oct 15, 2019 9:27 pm
by Sualdam
New user alert.

I recently received my RTL-SDR kit including the V-dipole set-up. The dipole is stuck on my window facing NNE, so I appreciate that right now the bulk of my house will be a problem with certain passes. But even so, when a satellite comes in heading SSE I have no trouble seeing the signal in Airspy.

Then I installed WXtoimg. I was surprised to find that out of the box it automatically recorded and (tried to) decode satellite passes (even the ones that there's no signal from due to being in the west and quite low). The decode is just noise as per this image
NOAA-19-10151522.jpg (1.95 MiB) Viewed 1349 times
. Or so I thought.

At this stage, I wasn't too worried and was about to start fiddling around. Well, actually I did start fiddling around, and noticed that the displayed thumbnail in the Audio Files tab of WXtoimg for this pass was this image
tmb_NOAA-19-10151522.jpg (16.95 KiB) Viewed 1349 times
It seems to be a perfect image of a cloud mass over the flight path.

What the heck am I missing here? How do I get WXtoimg to decode to a full image like that? Any pointers to the settings I need (or posts which cover that specific topic? I have searched, but didn't come up with anything.

I'm using essentially default settings, but with Baykal as the receiver type. I installed a virtual audio cable and set both Airspy and WXtoimg to use that.

Any advice would be gratefully received.

EDIT: It may be a generic image, but I can't see why it only does it for NOAA-19.

Re: WXtoimg Decoding

Posted: Thu Oct 17, 2019 10:11 am
by Username
It seem the Signal is Crap.
What Antenna and LNA do you use?

Re: WXtoimg Decoding

Posted: Thu Oct 17, 2019 3:43 pm
by Sualdam
Right now, it's just the dipole. I have an LNA4ALL on the way, and some aluminium bar so I can make a dipole to mount away from the house with a view to roof mounting it if I get good results.

My question was more to do with that thumbnail, though. I, too, had concluded the signal was "crap" when I first saw the main image, but when I stumbled across the thumbnail... that's when I decided to ask. The signal shown in Airspy during transit is quite clear - though admittedly not as strong as some users' videos have shown theirs to be.

Any genuinely "crap" signals only show as crap in the thumbnails, including NOAA-19 passes on the wrong side of my house. The NOAA-19 one heading SSE that is in open sky above me doesn't, and yields those detailed thumbnails. That got me wondering about WXtoimg settings.

Re: WXtoimg Decoding

Posted: Fri Oct 18, 2019 1:31 pm
by K3RLD
This isn't going to be helpful to you, but I have also seen funky behavior by WXtoIMG when receiving perfectly good (and strong) signals. Not sure what operating system you are using, but I can't get decent images at all running the gui on Ubuntu 18.04, yet get perfect images when running headless on a raspberry pi running jessie. :?

Re: WXtoimg Decoding

Posted: Fri Oct 18, 2019 3:09 pm
by Sualdam
That's interesting. I was planning on eventually moving it to a Pi dedicated to the task, so maybe I'll have a look in that area if the DIY dipole and LNA idea doesn't fix it.

I just had another one now - highly distinct signal during most of the transit, but still the same meaningless noise pattern displayed in WXtoimg. No detailed thumbnail either, this time. In fact, since the two I mentioned in the OP, I've had no such thumbnail images.

Mine's running on Windows 10 right now.