10 GHz - the line of sight band that isn't!


Everyone knows that 10 GHz is a line-of-sight band.

WRONG! - it just isn't. Perhaps the myth comes about from the days of low power, low receiver sensitivity designs based on Klystron or Gunn devices, where output powers would be limited to a few tens of milliwatts, and receivers would have diode mixers with no preceding pre-amp. With these set-ups, you can add 40dB to the link budget straightaway.

In addition to the usual refraction modes (see the WinRad screen shot below, for example), rainscatter provides a fairly regular enhancement. particularly in the UK... It has the characteristic effect of broadening a signal, rather like VHF auroral propagation, and is noticeable on narrow-band modes such as CW and SSB. It is multipath in nature. On a really overcast day, it is not unusual for a signal to be copyable no matter where the dish is pointed. Also with rainscatter, there is usually differant rates of doppler shift with incoming direction, so on CW the pitch will change slightly with antenna rotation.

There are a number of 10 GHz beacons in the UK, and GB3CCX, at 155km, can pretty much always be heard here. It runs 250mW ERP. Other beacons can be found here, on Peters excellent site.



GB3CCX - signal is shown some 30/40dB above flat condition level