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Re: This Weekend in Minneapolis: Central States VHF Society Meeting



Ed:

I thank you for your questions and comments.   As I said in my answers 
to Stefan's questions,  this will be an open engineering design and all 
members and interested folks will be able to see the documentation we 
have put together to support our work and designs.  We are justifying 
every one of these engineering decisions with cold hard calculation, 
supported by open peer review.   Following that,  all members will be 
able to see the documentation.  We do not have a single engineering 
drawing for the "new Eagle" outside of the great work Dick has done on 
the module boxes for the experiments.  ALL that happened in San Diego 
was we did a lot of calculation and design that leads us to the 
conclusion: if we are to build a satellite that supports the AMSAT 
functional requirements and vision statement with a credible machine, 
based on sound engineering principles, here is what we believe the 
payloads must look like.  I make my humblest possible apology in 
advance, but this does not include  "we will add modes and frequencies 
for which users have equipment where we know from calculation it is not 
supportable by calculated link margins,  limited spacecraft power, and 
the envelope we must fit on the rocket to get a launch".

I am extremely proud of the engineering team AMSAT has working for it as 
volunteers.  In many ways it is "best ever".  It includes former V.P. 
Engineering back to the beginning and there are several new faces,  many 
you all will see more and more of.  They are tremendously important to 
the process and are doing a truly outstanding job for us.  Believe it or 
not,  a couple of them were not born when I worked my first satellite!  
In general,  my greatest personal success in the last year has been 
asking for and getting help from the finest RF, and digital design team 
AMSAT-NA has ever had, and helping us to focus on credible engineering 
designs.  It is much more important than any personal technical work I 
have done. I believe it will lead to a successful multi-year effort to 
produce a usable satellite that is of sound design.

We are working hard towards putting together a "first look" basic design 
in time for the annual meeting in October.  WE WILL NOT be scooping that 
in the AMSAT-BB but will attempt to open the flood gates then.

Bob
N4HY



Edward R. Cole wrote:
> Bob,
> Thanks for your quick reply.
>
> I guess my reaction and comments were in anticipation of what you may hear
> from a lot more satellite users.  The satellite community was "forced" by
> the failure of mode-V on AO-40 to embrace microwaves and equip for mode-S.
> I would say that many have found the process less "painful" and the mode
> more useful than they anticipated.  So I was not writing just as a "rural
> ham".
>
> But now it appears we will have to go thru a similar process each time a
> HEO is launched.  I am a mw ham so this generally is more acceptable to me,
> but I also have a "painful" reality to face: living on 50% of what I
> currently earn about the same time that Eagle will launch.
>
> I understand that engineering projections show the 1270 and 2400 MHz bands
> becoming unusable by hams.  From what I hear 5 GHz will be quickly
> swallowed up by WiFi as well.  This is quite discouraging.  Frankly, I do
> not understand why the current GPS satellite system is inadequate for
> European use.  I am building a 1296 EME station at present and this sounds
> like it will end up a total waste of money.  1296 EME is currently probably
> the best band for eme in regards trade-offs of antenna size, cost, vs.
> low-noise environment.  So long low noise!
>
> Getting back to the mode-S issue, the presentation states that telemetry
> will use S2 downlink.  It was my suggestion that a circuit path from the
> mode-U receiver be provided to the mode-S2 exciter.  As I read it
> everything is to be done digitally in SDX so this would not seem to require
> much.  Is the problem that S2 Tx is only PSK?  I gather that this downlink
> is considered immune from 2.4 GHz WiFi interference (?).
>
> BTW you made no reference to my questions about bands above C-band.
> Perhaps a UX or SX transponder could be included in the design since you
> state that everything is still at the design level.  I understand if this
> is not physically possible or if the energy budget makes it undoable.
> 10-GHz as a downlink band is presently available without extreme ham
> engineering.  It used to be considered an "experimental" band but is
> becoming quite populated by hams.  This is the highest frequency that isn't
> experimental for hams.  I believe by 2010 that X-band may be as "easy" to
> equip as S-band was for AO-40.  A lot of hams did that.
>
> 73's Ed - KL7UW
>
>   


-- 
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
"An expert is a man who has made all the mistakes which can be
made in a very narrow field."  Niels Bohr
----
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