WSPR'ing on 160m

8 posts / 0 new
Last post
f6irf
f6irf's picture
Offline
Last seen: 9 years 2 months ago
Joined: 2008/04/18 - 12:24
WSPR'ing on 160m

Hi all,
Those notes are for WSPR'ers, interested by the "top-band" but who have a limited experience of it. The 160m SAD is on Nov 26, so get prepared !

On 160m the main problems are:
- The "man made" noise: moving from 80m to 160m the noise-floor increases by some 8dB to 9dB (based on CCIR report 258 / VOACAP for a "residential" noise floor of -145dBW @3Mhz).
- The antenna efficiency: On 160m, for most of us, the

horizontal antennas are generaly too low and the vertical antennas generally too short, which means low efficiency. For example my 18m vertical has an estimated gain of +2dBi on 80m, and if falls to -3 to -4dBi on 160m (*)

Even if the path attenuation is somewhat lower, there is a penalty of at least 10dB between 80 and 160. Which means that a higher TX-power is required.
IMHO, for a given path, if you run 5W on 80m it is quite logical to run 50W on 160m, to have some chances of success... (but don't worry, 5W will work OK for continental distances).
Fortunately, on the RX side, the problems are completly different, as the noise is high, even an antenna which has a very low efficiency will have equivalent performances as a highly efficient antenna... Only the directivity is important (what ON4UN defines as MDF and W8JI as RDF). More directivity, less noise-power captured by the antenna (assuming the noise comes from all directions at equal level, both in the horizontal and vertical plans) (**). So even, with a poor antenna, you should be able to hear as well as stations who have a better one in terms of gain (depending on your local noise floor).

A good point is that the WSPR segment is very quiet: in EU, just occasional PSK-stations in the evening and some splatters from domestic SSB QSO's. Also, all RTTY major contest start at 80m, therefore outside CW/SSB contests, the second half of the night is really quiet !

CU on 160m !
Pat

(*) Based 1) on simulation 2) on noise-floor measurement. If my antenna efficiency was 100% on both bands, I should see 8 to 9dB more noise on 160m than I see on 80m. I only see 3dB... Therefore, the gain of the antenna is 5 to 6dB lower on 160 than it is on 80m, due to a lower efficiency (ie ground losses, as my radial system in not wide enough for 160m).
(**) see:
http://www.w8ji.com/receiving.htm
http://www.k7tjr.com/rx1comparison.htm
Or ON4UN's bible !