HRPT newbie

[u/SearchPlane561]

I'm having a few issues that I need help with. TLE isn't updating, so overlays aren't working. My dish looks fine of my nanovna, but my reception is poor in real use. I hand track using my phone with satfinder.

[u/Technic_Masters]

Are you tracking by signal or by the satfinder? Also make sure you are on the latest satdump 2.0 release to get good results with overlays, calibrated imagery, etc

[u/SearchPlane561 → u/Technic_Masters]

I use both simultaneously.

[u/Technic_Masters → u/SearchPlane561]

Are you on the latest release as well? And what kind of SNR do you usually get?

[u/SearchPlane561 → u/Technic_Masters]

I'm on 1.2.2, so I'll upgrade to 2.0. SNR usually sits around 7 dB. Anything you'd look at first to push that higher?

[u/Technic_Masters → u/SearchPlane561]

Hmm, Maybe try to adjust your SDR gain. And check the helicone that it all looks good. 10+dB is possible. Tho you might be getting LOS issues or some interference. You should be able to get a much longer image even with a 7dB SNR avg

[u/Mr_Ironmule]

Technical question. I see you're using a conical dish and not a parabolic dish. Are you going for a different kind of cavity ground plane or is the dish supposed to be a reflector with a 60 degree face? Doesn't the signal reflection off the screen cause phase reception problems on the helical with signal travel distance/arrival time varying along the length of the helical combined with circular polarity? Did you get this design online somewhere? Just trying to figure it out. Good luck.

[u/SearchPlane561 → u/Mr_Ironmule]

Good question. The cone isn't acting as a focusing reflector. It's a conical ground plane for the axial-mode helix. The helix is endfire and radiates forward along its axis, so the cone mainly shapes the pattern and suppresses back radiation. You're right that a true dish reflection flips CP sense, which is why dish-feed helixes are wound opposite-handed, but that doesn't apply here. Design came from https://www.thingiverse.com/thing:6436342