[amsat-bb] Re: Frequency advice requested

[Stan W1LE]

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
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