[amsat-bb] Re: The Moon is our Future
nss at mwt.net
Thu Jul 2 06:20:42 PDT 2009
>Theoretically we may have a free ride to the Moon for an Amateur radio repeater!
>We need a simple Mode-J transponder (2-meters up, 440 down).
>Low power consumption.
>Assume minimal antenna gain from the Lander (3 dBd on each antenna)
>Assume transmitter power 5-10 watts.
Why go with the minimal antenna gain? From the moon the whole Earth
only displays less than 2 degrees in the sky. ( Moon shows 0.5 degrees
Why spill all the power where people are not?
In addition, once the antennas are positioned, that's more or less
it. There is a slight wobble (Libration) of 6.5 degrees So any
antenna with a 3 db point that exceeds 6.5 degrees is just wasting
And with this link budget even an active bird that has landed and not
flying it still will need some pretty hefty power to not need a major
antenna setup on the earth side of the system.
Just remember what an Oscar 10 station took to have reliable
communications,, At Apogee it was only 35,000 miles away, the Moon is
almost a ten fold increase in distance, to keep the lander from having
to run hundreds of watts to be heard on the earth, ever DB of antenna
gain will be needed for sure!
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