[amsat-bb] New baseline for GEO

[Bob Bruninga <bruninga@xxxxxxxx>]

> ...if you use 10m for the downlink, ... throw in 18 dB of atmospheric
> noise....  That is why we only planned to use 10m for uplink (where it
> has hardly any noise out at GEO)...

I was wrong.  Its galactic noise, not atmospheric so its just as bad at
GEO..  Back to square one.  As N4HY says, only advantage is the cheaper
Killowatt AMP at 28 MHz if you  can get one...

So here are my new link budgets for the FM transponder workable with an
Arrow Antenna.  THey are the same both ways, since you just swap the 0 dB
satellite antenna for the higher gain Arrow antenna.  (On 10m you need a
full size 3 element beam)... and change between 50W on the ground..

LINKS to an ARROW ant      For 10m   For 2m  For 70cm
-------------------------  --------  -------- --------
TX power         20          43 dBm   43 dBm   43 dBm
TX Antenna Gain               0 dBi    0 dBi    0 dBi
Polarization loss            -3 Db    -3 dB    -3 Db
Resulting EIRP               40 dBm   40 dBm   40 dBm

Path Loss at  2 m          -153 dB  -167 dBm -176 dB
Receiver Antenna Gain        10 dBi   10 dBi   13 dBi
Received signal            -103 dBm -117 dBm -123 dBm
Required for 12db SINAD
  in 3 KHz bandwidth       -121 dBm -121 dBm -121 dBm
Sky noise                    18 dB     3 dB   none
-------------------------  -------- -------- --------
Margin                        0 dB    +1 dB    -2 dB

Notes:
 - The uplinks from a 50W mobile rig will be 4 dB better
 - The downlink can only be on a small percentage of time
   because a 20W RF amp will likely draw 60W of DC power
   and only about 10W average will be available...

Again, there will be two uplinks, one for net control (priority) and one
for the net...

de WB4APR, Bob


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