Bruce: 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 Company.
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.
Regards, Joe, K7ZT
----- Original Message ----- From: "Bruce Robertson" broberts@mta.ca To: amsat-bb@amsat.org Sent: Thursday, September 07, 2006 5:06 Subject: [amsat-bb] S band and Eagle: an appeal for a higher level discussion
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 VE9QRP _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb