Hello Graham,
Anywhere in the 5830 to 5850 MHz band is a real "odd ball". IMHO No commercial ham, RX only ,block down converters in that band are available today.
So: Pick a RF freq so the Rx LO can be phase locked (with low phase noise), to an external reference. If frequency stability is of concern.
Pick a RF and we shall follow. ( Thanks for the leadership.)
Pick a RF, on or about, where others are planning, so my RX downconverter can be used for multiple sats.
I would probably start with a cost effective gridded dish, linear polarization. Though ideal feed may be circularly polarized.
Since the beacon will be fixed in frequency, the RX could use a low beat (RF - LO = IF) mixer technique or a high beat (RF + LO = IF) with only a minimum of operator (headspace) issues.
Select a LO that will not have any spurs in any other ham band.
Select an LO that can be used for multiple microwave bands. Satellite, terrestrial, EME, whatever....
First look: (nothing magic about 5830 MHz just a starting point)
5830 - 144 = 5686, /5 = 1137.2 MHz 5830 - 145 = 5685, /5 = 1137.00 more opportune freq to phase lock for stability. ala N5AC LO board
5830 - 70 = 5760 MHz down convert to the 5760 terrestrial ham band, easier to get a clean LO at 70.0 MHz
5830 + 4538 = 10,368 MHz upconvert to the 10 GHz terrestrial band
5830 + 4621 = 10,451 MHz up convert to the proposed 10 GHz sat down link, P3E
5830 - 3526 = 2,304 MHz but not an international operating freq
5830 - 4534 = 1296 MHz down convert to the 23 cm band, 4534 /4 = 1133.5 MHz
5830 - 5394 = 436 MHz , 5394 /2, then /3 =899.0 5830 - 430 = 5400 MHz, /6 = 900.0, may be nicer to phase lock with lower phase noise. 5836 - 436 = 5400
Forget 222 and 903 MHz as an IF, no international appeal.
Nothing yet pops out as ideal.
Why just a beacon (CW ID only) ??, Why not a fixed freq, multichannel downlink. Some interest in a CWID beacon, but it is like watching the grass grow. Lot more interest in down link that folks can participate in or that changes content, like telemetry, etc.
A U/C or S/C (more complex) transponder would be very interesting and would spark a lot of interest. A "bent pipe" FM (single channel like AO-27) U/C transponder may be easiest.
Initial thoughts, Stan, W1LE
Graham Shirville wrote:
Hi all,
AMSAT-UK is involved with the development of a "C Band" beacon to be deployed on a satellite in low earth orbit sometime during 2012. The satellite is ESEO - The European Student Earth Orbiter and the beacon will be part of an amateur package which will also include U/S and U/V linear transponders.
The beacon has to be somewhere in the 5830-5850MHz part of the band as this is the allocation that is available for space to earth transmissions. So the question is - what would be the best part of the band to use - taking into account existing ground equipment and antennas (if any) and potential QRM from other terrestrial systems.
Any ideas or suggestions will be most welcome!
thanks
Graham G3VZV _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb