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Antenna feed line length question

Posted: Wed Jan 10, 2018 8:20 pm
by Greg33
Hi All,

I'm new to the world of SDRplay (just ordered the RSP2). My questions mostly relate to the distance of the feed line I can potentially use between the SDRplay and my external antenna.

The only listening post available to me is not ideal - a room inside a concrete structure, approximately 5 meters from the nearest door/window and the eventual external antenna. Is this distance going to be too excessive? I mainly plan to listen to signals below 20MHz to begin with (MW & SW), but eventually would like to have an antenna for VHF as well (primarily to receive aviation broadcasts).

Would I be better off trying to place to RSP2 closer to the external antenna and getting a longer USB cable or would that be a drawback? I've successfully used USB devices up to a distance of 3 meters in the past, but not sure if that sort of distance would be too detrimental for the RSP2.

Thanks, Greg

Re: Antenna feed line length question

Posted: Wed Jan 10, 2018 10:31 pm
by g1hbe
With just 5 or 10 metres of feeder on HF you'll be fine, even with standard RG58. The loss will be quite small. However, if you plan to listen on VHF/UHF at a later date, the situation becomes more complicated. Your HF antenna will not do for VHF/UHF so you'll need two antennas (at least!) and a feeder for each one. Feeders for VHF/UHF need to be somewhat better than RG58. I use satellite coax type CT100 for all my listening duties as it is cheap, low-loss up to the low GHz bands and easy to work with. It is also well-screened.

Re: Antenna feed line length question

Posted: Tue Jan 16, 2018 11:26 am
by CaptainNemo
I live on the second floor of a five floors concrete building.
Antennas are on the roof and I have no less than 30 meters of RG6-like coax from the local tv/sat shop.
I have a lot of fun from 77 k (time signal) to 260 M (milsat pirates)
With this kind of rig sensitivity is not an issue. The problem is noise...
Bye