[amsat-bb] Future satellites

John B. Stephensen kd6ozh at comcast.net
Sat Jul 4 22:51:46 PDT 2009

An interesting question for the short term is what can we do with 1 watt of 
RF from a LEO satellite. RS-10 and RS-12 were interesting as they required 
only omnidirectional antennas but they had a lot of power available as they 
were attached to much larger satellites. AO-16 was a small satellite but was 
capable of only 1200 bps data using uncoded BPSK and simple vertical 

Given the type of hardware developed for Suitsat-2, we should be able to do 
a lot more. Using modern error-correcting codes 4800 bps is possible using 
omnidirectional antenas and with modern codecs that can carry 4 voice 
channels or 3 voice channels plus 40 PSK31-like channels. With 10 dBi of 
gain at the ground station the data rate and number of voice channels could 
be quadrupled. The downlink could also be split between 2 voice channels for 
use with omnidirectional antennas and 8 voice channels for high-gain 



I have extracted from it the most important following part:

73" de

i8CVS Domenico

Extracted from G3RUH article "THE EARTH MOVES"

> An example, 1 watt transmitted from a 20 dbi gain dish on the Moon,
> received on a 1.2m dish at Earth with a system noise temperature of 100K
> results in a signal to noise ratio in 2.4 kHz bandwidth of 10.5 db. (Note
> that frequency matters not). This would support one rather noisy SSB voice
> signal.
> Alternatively it would carry an error-free 2400 bps binary PSK data
> transmission without coding, 9600 bps with modest coding [2].

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