Changing coaxial cable on Solar Cooker Radio Telescope at LRO 2/1/2025
andrew....@googlemail.com
My son and I have changed the coaxial cable on my 1.5m parabolic solar cooker radio telescope from 5m of RG58 coaxial cable to similar length of LMR400 coax and – wow! The signal strength shot up dramatically, the signal was far smoother and RFI seemed to be less of an issue instantly!!!
Mind you, the coax cost more than the parabolic dish…….
So the parabolic solar cooker radio telescope (LRO-H2) now consists of:
1.5m parabolic dishà5m of LMR 400 coaxial cableàWT Microwave 1420MHz+/-2MHz cavity filteràNooelec SAWBird H1 LNAàcomputer.
Currently, I am collecting data on this telescope using SDR#/IFAverage (have eventually got around the testing the setup using this software, Alex!).
Will be interesting to see whether the output is better or not.
Can anyone comment on whether the 2 x filters should be:
(i) 1.5m parabolic dishà5m of LMR 400 coaxial cableàWT Microwave 1420MHz+/-2MHz cavity filteràNooelec SAWBird H1 LNAàcomputer.
(ii) 1.5m parabolic dishà5m of LMR 400 coaxial cableàNooelec SAWBird H1 LNAàWT Microwave 1420MHz+/-2MHz cavity filteràcomputer.
Andy
Marcus D. Leech
Dish-feed->LNA--->coax--->filter--->receiver--->computer
5 meters of LMR-400 has a loss of almost 1 full dB at 1420MHz--that translates to an extra 70K of additional Tsys if that much
cable is *in front* of your LNA.
Similarly, filters will have an insertion loss, and typically that insertion loss goes up as the bandwidth becomes narrower.
My guess is that your narrow-band filter has a loss above 1dB, so another 70K of additional Tsys.
The order that I describe above is what one would expect. The only thing that could be an issue is that you might still
need that narrow filter *in front* (ugh!) of the LNA to keep it operating linearly in a heavily RF-polluted environment.
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