[amsat-bb] Re: Allocations in L-band

Trevor . m5aka at yahoo.co.uk
Tue Nov 20 02:10:21 PST 2012


--- On Mon, 19/11/12, Richard Ferryman <g4bbh at btinternet.com> wrote:
> Just curious - Can someone enlighten me as to why there is no allocation 
> for satellite downlinks in L-band (at least in the bandplans I have seen).
> There are uplinks around 1267 to 1269 MHz. Is it due to possibility of 
> interference with commercial/military/aeronautical systems?

I believe it dates back to a WARC conference in about 1971. Prior to that the Amateur Service had I believe been able to use any Amateur Frequencies just as they can still do for that other form of Space Communication - Moon Bounce (EME).

Wayne Green W2NSD does make references to the loss of satellite frequencies a few times in his column in 73 Magazine from that era, see 73 Mag archive at http://archive.org/search.php?query=73%20magazine 

Although a separate service, the Amateur-satellite Service, was created they were only given access a limited sub-set of the Amateur Service frequencies. For the UHF and Microwave bands the satellite segments were all remote from the terrestrial weak-signal segment meaning separate equipment had to be built to work satellites. Back in those days even 435 MHz would have seemed "remote" from the 432 MHz weak-signal area due to the use of 28 to 432 MHz transvertors that only covered a narrow 2 MHz segment of the band. We share 432-438 MHz with commercial SAR satellites but why in the 70's we weren't allowed to use the whole of 432-438 I do not know. Maybe no-one thought to ask for the whole segment ?

The same with 1260-1270, why it's there I don't know perhaps someone can enlighten us. The band 1260-1300 MHz is used for wideband Global Positioning transmissions from Galileo, see 
http://www.southgatearc.org/articles/galileo.htm

Do restrictions that were applied to the Amateur-satellite Service 40 years ago (but not to Moonbounce) still have any relevance today ? again I don't know. 

Ideally the Amateur-satellite Service should have access to the weak-signal segments of all the UHF and Microwave bands for both Earth-to-Space and Space-to-Earth so we would only need to build one set of equipment on each band for both terrestrial and satellite working. It would be good if IARU were to work towards that objective.

73 Trevor M5AKA




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