23cm amateur band under threat
There has been a problem bubbling around for a while with amateur usage of the 23cm band, ever since an Italian satellite ground station suffered interference from an amateur repeater. The RSGB recently submitted input to Ofcom in preparation for next year’s World Radio Conference, WRC23.
The problem is that we are only secondary users of 23cm and the band can only be used providing there is no interference to primary users. Unfortunately the band’s is allocated to Radio Navigation Satellite Systems (RNSS) as the Primary users. These include the EU Galileo, Chinese Compass, Japanese QZSS, Russian GLONASS and at the very bottom of the band US GPS. It appears that 23cm may be in use for high accuracy (commercial and possibly military) services.
There are a number of proposals being put forward to the ITU. Taking away the amateur allocation isn’t possible at WRC but severe constraints are. Current proposals include:
1 Allow higher power operations (100W) in the range 1298-1300MHz plus….
• ….allow higher power (100W) spectrum for ATV (Digital only) at 1250-1254 MHz plus…..
• …amateur satellite higher power operation (20W) in 1260-1262 MHz…..
• …5mW power limit across the remaining parts of the 23cm band.
2 Remove ATV operation across the centre of the GALILEO band
• …identify a small low power segment for FM voice channels around 1293 MHz.
3 Limit all amateur eirp to less than 1W across the entire band
A number of IARU groups have been investigating the susceptibility of receivers to amateur signals. Perhaps unsurprisingly, some receivers are a lot more susceptible than others. Also the nearer the signal is to the centre of the satellite operator’s allocation and the wider the amateur signal’s bandwidth is, the worse the interference.
We’ll have to wait for the outcome of WRC23 but it looks as though significant changes are likely. It may be worth holding off from any significant investment in 23cm kit until we know.