Bob, I am very worried about this huge requirement for power. I am concerned that we are making a satellite that that AMSAT will not be able to afford.
We also need to resolve the question of how much power needs to be supplied during the worst case eclipse scenario. This has a major impact on the amount of energy storage is required.
Another question is whether we are going to stay with the requirement of being sun angle neutral. These are all drivers for the size of the spacecraft and the structure.
Lou McFadin W5DID w5did@mac.com
On Apr 27, 2007, at 3:30 PM, Robert McGwier wrote:
Bill Ress wrote:
Bob,
I don't think we'll find a device on the current marketplace that will suit our efficiency needs. But, if we're willing to develop (fund) a program to design and build a Class E, 1 watt, 5.7 GHz amplifier module, we might get to 70 and maybe 90% efficiency. I have seen Class E X Band amplifiers with 60 to 70%. The design, including the choice of active device(s) must start with the goal of being Class E since several interesting parameters are in play. You just can't take a Class C amplifier and "push" it into the switching mode. Perhaps a Class C amplifier might be enough.
I am listening and more than willing to consider anything that gets the job done with a reasonable budget.
But it's a very interesting design challenge - to be sure!! When do we start??
But, lets assume that we build amplifiers with 100% efficiency. 36 or 43 elements still requires 36 to 43 watts input. What has me concerned is that the current satellite structure design calls for 6 solar panels with, what I guess is about 25 watts per panel. That appears to be consistent with the 100 watts power generation stated in the current Eagle Functional Requirements.
Are we still working with 100 watts or did I miss something??
What we are working with is "whatever we can get away with" so long as it meets the communications systems goals as stated in our working document from the San Diego meeting of last summer. That is the system we want to design and the concept we wish to support. If this involves us working on our own amplifier design, and not using monolithic designs from Hittite, etc., so be it. The efficiency translates directly to multiple scenario big wins for us. Class E for this is completely acceptable.
Regards...Bill - N6GHz
Robert McGwier wrote:
The Hittites were interesting, they had potential, but they are not really efficient enough. We will find better parts.
Bob
73's Bob N4HY
-- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle