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I've encountered some challenges with my ground station intended for receiving images from GOES satellites, and I'm seeking your expertise to troubleshoot the issue. Here are the system specifications:

  • Dish Size: 1.9m
  • GOES Frequency: 1691.4 MHz
  • Satellite Elevation: 66
  • degrees 22dB Wideband LNA (1.5 to 2.5 GHz) directly connected to the feed, powered by a Bias-Tee
  • 3m M-M N-type RF cable with a 0.6dB cable from the LNA to an F-F RF adaptor
  • 50m M-M thick RF cable from the RF adaptor to the radio, with a 6dB loss at the L-band

Despite these specifications, I haven't been able to detect any signals on my SDR receiver. Our initial troubleshooting involved addressing pointing errors, confirmed by referencing the sun. The cables were tested with a yagi, successfully receiving packets from UHF satellites.

One area we're exploring is the focal length. The dish's manufacturer recommends 85.5cm, but our measurements indicate a depth between 28 and 30cm, corresponding to a focal length of 75.21 to 80.58cm. Could this discrepancy be causing the issue?

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  • $\begingroup$ If the feed is a helix, it's not ideal to mount it the way you have - the metal ring may interfere with the helix, especially with it like the third photo. Can you hold it right at the back, around the thick portion? Also the feed says f/D of 0.45, which makes sense as a helix has a fairly narrow beam. It's difficult to feed such a flat dish with a helix. These two effects will reduce the dish gain, but not make it completely deaf. $\endgroup$
    – tomnexus
    Commented Dec 13, 2023 at 7:19
  • $\begingroup$ GPS satellites should make a good test source, there are many of them and they have 10s of watts, RHCP. They should easily be visible at 1575 if you point the antenna at them. $\endgroup$
    – tomnexus
    Commented Dec 13, 2023 at 7:20
  • $\begingroup$ Does your LNA have a bandpass or highpass filter on it? A helix like that will be quite sensitive and omni-directional down to 100 MHz, very different to a horn feed. Without a filter, if you live near a city, the LNA may be completely saturated by FM, TV or cellphone signals (take a look with your SDR). $\endgroup$
    – tomnexus
    Commented Dec 13, 2023 at 7:24
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    $\begingroup$ Last question - if the dish is 1.9 m diameter... the photos make it look like the feed is 1.0 m away from the dish. The feed phase centre will be 5 or 10 mm in front of its back surface, with the label on it. If the feed is 200 mm long its front will be ~600 mm from the dish surface. Is it mounted roughly in the right place? 5 cm error won't spoil its gain and pattern too much (especially as you're under-illuminating it) but 2x F will be pretty bad. $\endgroup$
    – tomnexus
    Commented Dec 13, 2023 at 7:35
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    $\begingroup$ Please remember that comments are for discussing improvements to the question, and that additional information should be incorporated by editing the question. $\endgroup$
    – Kevin Reid AG6YO
    Commented Dec 13, 2023 at 20:32

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