Hmmpf. Wonder what I was doing wrong? I had a 5 element yagi at the time, upgraded to an 8, and still hardly heard anything out of the bird. The one contact I had was when the satellite was only a few thousand km up. The 8' boom on the 2m antenna is the longest my roof tripod will take. Part of the problem probably was the 60' of RG-213 to the Shack. I now have some old hardline in its place, but that came after it was too late. Perhaps I'll get another chance with the new birds...
I handle the "smoke" problem by using an ICOM R-7000 receiver for the S-band IF. Deaf, but it also doesn't transmit.
Greg KO6TH
----Original Message Follows---- From: "Gary "Joe" Mayfield" gary_mayfield@hotmail.com To: amsat-bb@amsat.org Subject: [amsat-bb] Re: S band and Eagle: an appeal for a higherleveldiscussion Date: Sun, 10 Sep 2006 23:13:44 -0500
It is a simple matter for a ground station to raise power and be heard above the din. Most WiFi are at the milliWatt level. It is hard for the satellite to raise power and be heard above the din.
I found AO-13 to be the opposite. My original mode B (V) antenna was not large, and was not near the wind load or weight of my small dish. Later I went to a larger Yagi, because I got "into" the ZRO tests.
A little simple math from the ZRO test.
Let's assume the downlink from the new bird will as good as AO-13 (I expect it will be better). With a 12 foot yagi I made ZRO 9 which is 27dB below the recommended signal level for QSOs. I will confess it was tough copy so I will give up another 3 dB just to be nice. So my 12 foot yagi (homebrew, not computer optimized) had 24 dB to spare. A six foot Yagi should have 21 dB to spare. A three foot Yagi should have 18 dB to spare.
We are not talking about large antennas. The Yagi does need proper care and feeding, but I never did smoke it by transmitting into it either.
Looking forward to mode B (U/V) again, 73, Joe
----- Original Message ----- From: "Greg D." ko6th_greg@hotmail.com To: amsat-bb@amsat.org Sent: Sunday, September 10, 2006 1:40 PM Subject: [amsat-bb] Re: S band and Eagle: an appeal for a higher leveldiscussion
{Tilt}
If 2.4 ghz pollution is going to be a problem for stations on the ground who are looking up (and away from) the noise, how is it possible that a satellite in the sky looking down on half of a planet's worth of 2.4 ghz noise, is going to be able to pick out one earthly station over the din? This is totally backwards in my mind.
Please, mode VS or US makes sense for the "installed base". Mode B suffers from a worse problem than the S-band noise: physics. The Mode B receive antennas need to be phyiscally large, and putting up large antennas is becomming a problem more rapidly than overcoming noise on 2.4. Small lots, CC&Rs, and other "environmental" factors are forcing hams to make do with smaller, less obtrusive antennas. I can solve the small antenna uplink problem on V with a power amp; I cannot solve the problem of a small antenna downlink problem on V, even with a preamp. I tried that when AO-13 was still up, and managed to get *one* contact. Really, I should be running LS. That would force me to get on 1.2 ghz.
Plus, noise on V is also getting worse by the day. For years I have checked into a weekly SSB net on 2m (144.250 8pm local on Sundays) and have noticed there has been a huge increase in noise coming from the populated areas. Like Bill, I live in the Sierra Foothills (Auburn for me), and overlook the Sacramento Valley. The noise peak from the direction of Stockton & Sacramento is amazing. 2.4 may be getting worse, but 2m noise is getting worse faster, and at least the laws of physics allow us to create S-band receive systems that can aim around (over) the din.
Greg KO6TH
----Original Message Follows---- From: Bruce Robertson broberts@mta.ca Reply-To: brobertson@mta.ca To: amsat-bb@amsat.org Subject: [amsat-bb] S band and Eagle: an appeal for a higher level discussion Date: Thu, 7 Sep 2006 19:06:17 -0300
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
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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
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_______________________________________________ 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