[amsat-bb] Re: S band and Eagle: an appeal for a higher level discussion

Eric H Christensen kf4otn at ericsatcom.net
Thu Sep 7 17:24:08 PDT 2006

While you bring up some good points in your message I feel there are
questions that remain in need of answering.

The first question that I have is where is all this data that was used
to produce such a theory of S-band pollution being too great for a HEO?
 I've seen data that I agree with that says that S-band uplinks would
essentially be deaf on a HEO due to the rise in the noise floor from all
of the non-licensed networks and such but that noise floor comes from
millions of such devices.  One would never have to put up with that much
interference at their home stations.  Until I see research data that
supports such a theory I cannot possibly stand behind such a decision to
cripple our next satellite.

Why should we buy a product that doesn't meet our needs and wants?  I
certainly wouldn't go out and purchase anything just because someone
else wanted me to.  My hard earned money goes into the products that
fulfill my wants, needs, and desires.  With S-band going away, and
another project possibly being scrubbed as well, I'm seriously
considering throwing my support and money towards the P3E project which
has an outstanding lineup of experimental bands along with the more
traditional ones on board.

Too bad this information didn't come out earlier as I'm sure it would
have been a great discussion piece for those that were running for Board
positions.  I wonder how many Board members would support the decision
of taking S-band off the future birds.  Members of the Board should take
note and realize that their time is coming to end with these kind of
decisions being made.  We pay the money to support AMSAT now where is
their support back to us?


Bruce Robertson wrote:
> There has been a recent restatement of disappointment regarding the Eagle
> design committee's recent choice to use S band as an uplink not a downlink.
> Note that the next two HEO's scheduled to launch *will* have S band
> downlinks, so there's no worry that people like I, who live in radio quiet
> areas, will be unable to use our developing S band equipment in the future.
> As I understand it, the Eagle design team have used standard predictions of
> 801.11 usage to determine mathematically that by the time of launch the
> radio environment will simply not support reliable communications. I cannot
> imagine that they like these conclusions. Implementing new bands entails
> new risks, after all. But numbers don't lie (or shouldn't), and it would be
> a horrible disservice to all of us if they designed and launched a bird
> that was effectively mute at launch.
> The design team have said again and again on this list that they would
> welcome contradicting evidence that is cogent, and I, for one, believe
> them. They're our volunteers, and they deserve our support. I can't provide
> that contradicting evidence: I'm not skilled or qualified. But I can assess
> an argument, and the responses so far have not been nearly as rigorous. 
> They have amounted to "works for me", which I think misses the point. 
> Please, please, those of you who are qualified and competent and hold the
> opposing opinion, take the design committee at their word and assess their
> work, check their assumptions, present cogent opposing arguments. There is
> some thought that a dish antenna properly implemented will overcome the
> obstacles described by the design team. Let's model this. Or those who live
> in heavy 802.11b environments, do some experiements with terrestrial links
> (which I suppose could be assumed worse than earth/sky). Who knows? Maybe
> it's all like my last tax return, where a missed decimal point made me
> think I'd have to take out a second mortgage to pay our taxes :-) This list
> and the wiki exist so that we can undertake that sort of dialogue, and for
> my part, it is my favorite part of participation in AMSAT.
> Some have suggested that Eagle fly with an S-band downlink on the off
> chance that it *does* work despite the theory; others, that we survey the
> members to see what they'd like. I fully support the design teams rejection
> of the former approach. Launch weight is very expensive and the kitchen
> sink approach is not to my mind sensible. As to the latter, a survey
> presumably pertains only to *working* bands, not ones that are polluted out
> of existance.
> It's human nature for us more readily to see our misfortunes as caused by
> the malace of others, but I think we should strongly avoid terms like "bait
> and switch". We'll get much further if we all assume the goodwill of
> everyone involved. 
> 73, Bruce
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