[eagle] Re: Another idea on phased array configuration

John B. Stephensen kd6ozh at comcast.net
Sat Apr 28 07:57:00 PDT 2007


Since the generated beam needs to cover the entire earth from a maxmum of 35,000 km in alttude, the beam can't be made very narrow. I don't think that all 36 or 43 elements ever need to be on at one time. Many could be held in reserve.

73,

John
KD6OZH
  ----- Original Message ----- 
  From: Louis McFadin 
  To: Robert McGwier 
  Cc: K3IO at verizon.net ; AMSAT Eagle 
  Sent: Saturday, April 28, 2007 14:36 UTC
  Subject: [eagle] Re: Another idea on phased array configuration


  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
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