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

Joe Westbrook k7zt at cox.net
Thu Sep 7 18:01:07 PDT 2006

Are you suggesting that "Please,, those of you who are qualified and 
competent"  are the only folks who are worthy of a dissenting view regarding 
this topic?  Please, that is precisely the attitude that turn folks off of 
AMSAT-NA, that elitist attitude has no place in a HOBBY.  Particularly when 
we ALL contribute to the construction of the satellites.  It just happens 
that I am a professional Network Engineer (Trainer) for a Telecommunications 

 My background spans virtually every communications technology from DC to 
Daylight.  I have an extensive background in EMI/RFI Labatory Testing, 
culminating in  35+ non-stop years in the Communications field.  No I don't 
have any matamatical studies, what I do  have is first hand empirical 
experience in a neighborhood where EVERY Home has at least a single 2.4GHz 
radiation source .

  I worked AO-40 and thoroughly enjoyed the S Band downlink and have 
maintained the station in anticipation of continuing this activity on the 
HEOs.  I'm not alone, I'm sure that the majority of members who have made 
the S Band and Investment.

Do I get interference from the IEEE 802.X devices and portable phones, yes, 
in the form of random clicks that are easily removed by using a noise 
blanker, try it works great!

What, if any studies considered that 5.2Ghz devices are taking off now and 
will probably eclipse the 2.4Gig interference levels.  Make any argument you 
wish for dropping S Band from Eagle, but don't use the polluted spectrum 
argument, it simply doesn't hold water.

Joe, K7ZT

----- Original Message ----- 
From: "Bruce Robertson" <broberts at mta.ca>
To: <amsat-bb at amsat.org>
Sent: Thursday, September 07, 2006 5:06
Subject: [amsat-bb] S band and Eagle: an appeal for a higher level 

> 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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