[amsat-bb] Re: The Moon is our Future

MM ka1rrw at yahoo.com
Thu Jul 2 06:41:00 PDT 2009

Hello Joe:
Thank your comments.
My EME experience is minimal.  I have only been able to hear a few signals from the Moon and have yet to complete a full 2-way EME (new antenna in progress).  I am sure there are some people on this emailing forum that have more experience than I have with EME communications.

The reason for a small antenna setup on the NASA lander proposal is because I believe it will be harder to convince NASA to allow us to install a 20 foot boom on the lander.

Right now this is the concept theory phase.
Is a 2m/440 SSB transponder practical?
If our analysis proves that it is not, then we can move on higher in frequency until we find an affordable solution (within the ITU guidelines).

The ground stations will need to be Oscar  class or better (12-15+ dBd).  
The question is, which frequency combination will give us the best bang for the buck and provide access to the most users?

A Moon repeater will never be accessible via a HT.  And with the exception of one (1) truck I saw, it will not be accessible to mobile SSB systems.

--- On Thu, 7/2/09, Joe <nss at mwt.net> wrote:

> From: Joe <nss at mwt.net>
> Subject: Re: [amsat-bb]  The Moon is our Future
> To: "MM" <ka1rrw at yahoo.com>
> Cc: kg4zlb at gmail.com, amsat-bb at amsat.org, "Jack K." <kd1pe.1 at gmail.com>
> Date: Thursday, July 2, 2009, 9:20 AM
> MM wrote:
> > Theoretically we may have a free ride to the Moon for
> an Amateur radio repeater!
>> [snip]
> > 
> > 
> > One theory:
> > 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 from earth)
> 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
> transmitter power.
> 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!
> Joe WB9SBD


More information about the AMSAT-BB mailing list