[eagle] Re: Another idea on phased array configuration

Louis McFadin w5did at amsat.org
Sat Apr 28 07:36:50 PDT 2007


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 at 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 at amsat.org
> http://amsat.org/mailman/listinfo/eagle

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