Wednesday, 20 January 2010

28 MHz WSPR

Today was 28 MHz day on WSPRnet. I was received by 22 stations, the furthest was EA1FAQ at 1390Km. 8 of those stations were in the UK. Most of these only received my signal one or two times so weren't the VHF type propagation that you might normally get on 28 MHz locally. One station, G0HNW in Holmfirth, West Yorkshire, was around the same signal all day so this seems like a direct path over hills of 111Km rather than 'skip'. The next closest station was G4EFS at Kidderminster, 201Km away. At the moment, 200Km is around the minimum skip distance I'm getting on most HF bands.
There is another station who I think I've got a direct path to on HF and that is GW4SDO near Wrexham, on 10MHz. The signal doesn't change over time and there isn't very much in the way. But like G0HNW on 28MHz, the SNR as shown by WSPR is very low (-20 to -25dB).
I'm interested by short distance HF propagation like this, probably from using CB where you need a HF band to behave like a VHF band to make local contacts. Apart from CB, the upper HF bands aren't used much for local communications in the UK, we have a 29 MHz repeater in Northampton but not much local activity on that band. With most of us living in built up areas, there is a lot more noise on HF than on VHF/UHF. The 25MHz broadcast band isn't a lot of use for international broadcasting at the moment but there is talk of using it for local stations with the DRM digital format (tests are being run in London from the Crystal Palace and Croydon sites). The sooner the better, and then we can get rid of the DAB system which is already outdated and of no interest to most people (in this area there is no local radio on DAB, neither BBC or commercial).
You could have 25KHz channel spaced stations using a decent codec which would give "mp3 quality" audio at 40kbit/s HEAAC sounds good at 40K). Hundreds of stations could be fitted on Band 3 in one city, with more room in Band 1, HF and unused TV channels. There would also be the old 88 - 108 MHz broadcast band if they ever do clear it of the analogue stations. Maybe it would be possible to run side by side in that band, with the digital transmitter on a frequency which would not be usable with a wide FM signal.

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