Hi W0JT:
I like your simple explanation of the path loss; it should help many understand that an Active Repeater on the Moon will not require as big of an antenna system as passive Moon EME station. Now we just need to run the path loss numbers a few different ways to see which Amateur Radio Band option works the best. If we are able to piggyback on a NASA funded Unmanned Moon lander, then we have the possibility of the least expensive flight to High orbit possible. This is an opportunity we just can not miss trying for. Our only other option for affordable high orbit flight may be with China. I believe the High orbit flights with NASA and EAS are now cost prohibitive. 73 Miles WF1F MarexMG.org --- On Thu, 7/2/09, tosca...@umn.edu <tosca...@umn.edu> wrote: > From: tosca...@umn.edu <tosca...@umn.edu> > Subject: [amsat-bb] Re: The Moon is our Future > To: amsat-bb@amsat.org > Date: Thursday, July 2, 2009, 11:52 AM > On Jul 2 2009, kd8...@aol.com > wrote: > > > Don't want to get a whole new thing started here but - > I don't think we > > ever went to the moon in 1969 and I don't think we > will ever goto the > > moon - in 2012 or whenever they proposed a "return" to > the moon > > With that level of disbelief I can certainly see why you > are predisposed to > discount the possibility of a moon-based transponder. > > > I would love to see an amatuer repeater on the moon > thou - from my > > understanding EME is expensive to do, so I think it > would leave most of > > us out > > Not necessarily. Remember, with conventional EME, you send > as large a > signal as you can muster towards the moon, incur huge path > losses along the > way, then incur a huge loss because the moon is a very > imperfect reflector > of RF energy, then incur the huge path loss back from moon > to earth. > > With a moon-based repeater, you send as large a signal as > you can muster > towards the moon, incur the same path loss from earth to > moon; BUT, THEN > you enlarge the signal with a gain antenna at the repeater, > and then have a > sensitive receiver that can detect and amplify the signal. > The repeater > then transponds the signal to a different frequency band, > amplifies it as > much as equipment weight and power availability allow, > transmit it through > a gain antenna, and only THEN incur the huge path loss from > moon to earth. > > Because the path loss is only in a single direction, and > instead of an > inefficient (lossy) passive reflector, you have gain > antennas for reception > and transmission, plus amplification on receive and on > transmit, the net > earth station requirements should be much less than > conventional EME. > > That's not to say it would be easy, just that it should be > easier than > conventional EME in terms of station requirements on earth. > As has been > mentioned numerous times already, the station requirements > for the space > end of the system are enormously more difficult than > anything we've ever > tackled so far with either LEO or HEO satellites. > > But there's no harm in DISCUSSING the idea, and learning > about the pitfalls > and possibilities as part of the discussion. Even if it > never comes to > pass, we should all be a bit more knowledgeable after > having had the > discussion. > > As far as the dreaming goes, wouldn't an L/S transponder be > better than a > V/U or U/V transponder? Granted, the path loss is greater, > but the antenna > gain is easier to produce... > > While I am a firm believer in the KISS principle (Keep It > Simple, Stupid!), > I am getting a little tired of hearing people complain > endlessly about the > downfall of AO-40 being due to its complexity. Uhh, the > downfall of AO-40 > was human error, which will ALWAYS be an issue. The only > reason that AO-40 > was ever usable at all was BECAUSE of its complexity, i.e., > the redundancy > of multiple transponders that could be switched into place > after initial > failures, etc. OF COURSE, a mission to the moon needs to be > as light and > compact as it can be made, and therefore much simpler than > AO-40, but due > to the harsh environment in which it would be asked to > operate, it needs to > be as complex as necessary to get the job done, i.e. not as > simple as AO-10 > or AO-13. > > 73 de W0JT > AMSAT-NA LM#2292 > > _______________________________________________ > Sent via amsat...@amsat.org. > Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur > satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > _______________________________________________ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
