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AM Satellite



> >AM on ham satellites????   Good god no!!!!   Cliff K7RR
>
> Obviously, Cliff, the hole in their heads is wider than the bandwidth
> on either FM or AM!!!       Dave

We like to think outside of the box so to speak... We chose an AM uplink
for our mode A satellite as follows:

UPLINK (UHF AM):
1) Its what our boats have and what they are currently authorized to use.
2) The lack of efficiency of AM on the uplink is meaningless, since the
   power is on the earth side of the link and the boats have 25W xmtrs.
3) With AM there is no Doppler tuning required on the AM uplink which on
   UHF otherwise would be almost 18 KHz
4) AM (6 KHz) is 3 times better in spectrum efficiency than FM (18 KHz)

DOWNLINK (HF SSB):
1) The downlink is very efficient SSB mode A in the 24 to 29 MHz band.
2) We can close the link with only 1 Watt from the satellite.
3) The boats also have HF SSB radios so there is 0 cost to the users.
4) We have $$$ to build a satellite, we dont have a dime to spend on
   upgrading the boats with SATCOM radios. (at $20,000 each)

We are quite proud of the project, especially since there are tens' of
thousands of low value assets like jeeps, tanks, trucks, and aircraft that
still only have a UHF AM tactical radio.  They will never be upgraded at
$20,000 each to SATCOM capability.  And even if the radios were free,
there is no way the current SATCOM channels can support communications for
these low priority users.

Thus, we found a niche to fill (demonstration only) and were able to make
a satellite project out of it..  Since many Hams are also members of MARS
organizations, we figured this satellite could also be made available to
them for experimentation.  After all, what good is a satellite if you
can't play with it..

http://www.ew.usna.edu/~bruninga/marscom.html

Unfortunately, it will only last 6 months or so due to the low orbit
opportunity... (and is more than a year from now)...

de WB4APR, Bob
Naval Academy Satellite Lab


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