Suggestions to improve VHF/UHF antenna

SatNOGS Hardware
1

Hi all,

I am looking for suggestions to improve the performance of my antenna. I am using a dual-band (VHF/UHF) Nagoya UT-308UV.

Current setup is: Antenna mounted on large metal roof → 2m rg58 cable (included with antenna) → RTL-SDR V3 → RPi (running satnogs client 1.8.1).

Things I have thought of…

  1. Somehow shortening the coax, although I feel I might worsen it if not done properly.
  2. Adding an LNA, but I feel adding this to the end of such a long coax would only amplify noise.

Here are some observations:

  1. SARAL
  2. NOAA 15
  3. SITRO-AIS-7
  4. FORMOSAT-7-4
  5. CUTE-1

Here are some pictures of the setup and SWR measurements in both bands:

nagoya_setup
nagoya_setup1920×1391 341 KB

In general it seems to get (noisy) NOAA data and for cubesats I manage to see beacons but not decode them. Do you have any comments on its current performance or suggestions to improve?

Thanks!

2

Maybe this link with some comparison and design options can help.

All the best,

Jan - PE0SAT

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3

The waterfall looks clean and pretty free from spurs and such, I’d say crank the gain up a bit.
rtl-sdr with gain: "16.6", without LNA in my experience might be low for a rtl, try 20-30 and see what happens.
monopole on a big ground plane have pretty good coverage but low gain, directionality is the tradeoff for gain.
Also, with such short cable to the SDR there might not be much to gain with LNA, depends on the nf of the LNA and SDR.
Placing a LNA as close as possible to the antenna, you can move the RPi and SDR to a more convenient location as the loss of the coax is compensated by the LNA gain.

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