[amsat-bb] Re: Re: RE: Geo Opportunity

[Keith N6ORS <k2@xxxxxx>]

>>On Wed, 30 Jul 2003, Keith N6ORS wrote:
>
>> ok, this is for a Mode K transponder.  21.4 mhz uplink /29.4 mhz dnlink.
>> Using 5w on the uplink (portable qrp type nuts) , and 10w (single
>> signal) on the downlink.
>
>Yes, but if you use HF for the downlink, you have to throw in 18 dB of
>atmospheric noise to the link equation which washes out all advnatages of
>the better link budget.  That is why we only planned to use 10m for uplink
>(where it has hardly any noise out at GEO)...
>
>I think...
>
>Bob
>>

OK Bob, 
well that pretty much settles it then, Mode KT (i think its mode KT)
21mhz up and 145mhz down
would seem to give us the most advantage but inverted Mode A 29/145
would have less activity 
on the uplink. So that looks like the ticket. Too bad , i have been
working on a mode K for 
a month or so and have it 80% designed.  

These numbers assume 10watts of tx on the sat.
A 5w rig with a wire on the uplink and arrow antenna on the downlink
would make a nice portable psk-31/hellschriber setup. larger downlink
antennas would make ssb workable.


Keith (N6ORS)


Uplink 10m
TX power          5W    40 dBm
TX Antenna Gain          3 dBi
Polarization loss       -3 dB
Resulting EIRP          40 dBm

Path Loss at 10m      -153 dBm
Receiver Antenna Gain    0 dBi
Received signal       -113 dBm
Required for 10dB SNR
  in 3 KHz bandwidth  -119 dBm
------------------------------
Margin                  +6 dB

Downlink 2m
TX power         10W    40 dBm
TX Antenna Gain          3 dBi
Polarization loss       -3 dB
Resulting EIRP          40 dBm

Path Loss at 70cm     -167 dBm
Receiver Antenna Gain    7 dBi
Received signal       -120 dBm
Required for 10dB SNR
  in 3 KHz bandwidth  -120 dBm
------------------------------
Margin                  +0 dB
----
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