Re: SDR & Red Devil
Posted: Mon Jan 07, 2019 3:55 pmxxjondoexx wrote: I have that cable while I wait for my RG58 50 Ohm coax cable, it was all I had laying around that gave me the distance I required. It was left over from an old ISP installation, it came from the demarcation point which I've re-purposed.
RG-58 Coax is acceptable in short runs on the lower parts of VHF, but at UHF it is going to be no better than RG-6 & if it's cheap stuff from a CB supplier then potentially worse.
100 feet of average RG-58.
150 mhz, loss of just under 55%.
500 mhz just under 80%.
With antennas we use compromise antennas for broadband coverage.
And although the antennas you link to are in some respects correct there are things to take into account.
The polarisation is important & if you get it wrong you will loose 3dB (50% of the signal.) Almost all VHF & UHF radio traffic is Vertically polarised. Satellite & amateur radio SSB traffic being the two most common non vertical polarised signals.
Edited to add. Long distance signals bouncing off the ionosphere are not as polarity important as the polarity is not stable on these signals.
For some satellite work you need a antenna that is adjustable both for elevation as well as compass direction. As not all satellites are low to the horizon.
Also to account for doppler effect on the signal, dual polarisation in a rotational pattern is used on some antennas. As doppler effect causes a signal to rotate, which is why you see some very strange looking antennas used on satellites at UHF. But the direction of rotation is important too, so it needs to be correct.