On Jun 18, 2008, at 5:38 PM, i8cvs wrote:
----- Original Message ----- From: "Mark Vandewettering" kf6kyi@gmail.com To: "AMSAT-BB" amsat-bb@amsat.org Sent: Wednesday, June 18, 2008 9:49 PM Subject: [amsat-bb] Re: LEO's
On Jun 18, 2008, at 2:46 AM, i8cvs wrote:
Hi Art, KC6UQH
You are correct 100% because the HEO AO40 was very easy to work using any old TX capable to run about 50 to 100 watt into 70 cm CW and SSB
A 3 to 4 foot dish with a 2400/144 MHz downconverter in the focal point and connected to any old 144 MHz CW/SSB receiver mounted on the balcony was sufficient to receive a nice downlink from all over the world by many users at the same time for many hours every day.
No complicated TX/RX radios and special software was necessary to compensate for doppler just made by hand.
Well, sure, if you want to reduce ham radio to just keying the mic, leisurely yapping along for hours at a time, then by all means, let's have more satellites in HEO. But where's the skill in that?
Hi Mark, KF6KYI
The skill is in building about everyting by yourself like low noise preamplifiers for 2 meters, 70 cm, 13 cm and high dinamic range downconverters for the above bands plus an Automatic Noise Figure Meters to get the best Noise Figure, build transverters from 2 meters up to the MW, build different type of feed for dishes having hours to test their efficiency through the HEO satellite in cooperation to many and many experimenters worldwide and discuss the problems with them improving your knoledge in radio-technique.
I can see that my attempt at sarcasm was apparently lost on some people. I suppose I'll have to explain more plainly. I suppose that means my little joke wasn't funny, since I have to explain it.
It's become trendy on this list to criticize LEO or FM sats. That's okay, as far as it goes. Yes, they are frequently congested. Yes, they have operators on occasion who are inexperienced, or what's worse, just don't care very much about operating reasonably. And they aren't up for very long, which often makes QSOs short. All of those are at least to some extent somewhat reasonable criticisms. They are reasonable in part because we can do something about them: we can encourage better operating procedures and work to educate people on the proper use of these satellites and thus ameliorate most of the problems (except, perhaps the most basic ones: the satellites orbits and transponders are what they are, and no amount of good operating procedure is going to change that).
Which brings up the first _unreasonable_ criticism. Complaining about either a) the fact that they are FM or b) the fact that they are LEO satellites. No amount of complaining will make this fact change. Ever. They are what they are. Those of you who would like to endlessly revisit this question can point out, again and again if they like, about how such FM/LEO birds are a waste of time. That has served been at least one "benefit": AMSAT-NA isn't the least bit interested in doing another FM satellite, or even a satellite in LEO. You guys won! It's over! AMSAT-NA won't be sending any of those birds up again, probably for my lifetime. Whether you thought ECHO was a waste of time or not, at least it ruined the entire notion of LEO permanently for AMSAT.
The second _unreasonable_ criticism is to complain about how anyone with an HT can push a button and work the FM satellites. That's not a problem: that's a feature. Not everything that is easy is pointless, and not everything that is hard is worthwhile. It's damned cool that I can hit the ISS with 5w into an omnidirectional antenna on my car roof, and use it for APRS messaging. It's cool that I can work Hawaii, or Alaska, or the East Coast or deep into Mexico using my HT and a handheld antenna, stuff I could toss into a backpack and go hiking. Is it hard? No, not especially. It's not a snap though, since I am operating with such low power. I find it kind of neat to talk to NH7WN in Hawaii, each of us standing outside in the wind holding handheld antennas and HTs on 5 degree passes. I could make it harder. I could use smaller antennas or less power. I've had QSOs over SO-50 with the lower power setting on my VX-3R before (300ish mw). That actually wouldn't be that hard either, except for the high power stations which like to transmit over others. But it isn't _hard_.
The fact is that there is _no actual reason_ that working linear transponders in LEO need be hard either. It's hard mostly because satellite communication is a niche market, so we have to make due with what we can get. So, we cobble together downconverters, amplifiers, preamps, computers and rotor controls together. Instead of a single box with a microphone attatched, we have two separate radios, perhaps each with their own amps/preamps and down/upconverters, and perhaps a computer to drive it all and aim the antennas. It _could_ be in one box. It _could_ use keplers to automatically correct Doppler for you, so that tuning would be no more difficult than spinning a dial. But nobody builds that box, and as near as I can tell, nobody in amateur radio is really interested in building that box, because they think that _the difficulty of something is what makes it valuable_. We see this all the time, when people talk about Morse code and criticize digital modes like PSK31 or the like. As engineers, we should be _ecstatic_ that using radio is simple, but instead, we choose to laud the efforts of doing things the same old hard way.
And here is the important thing that the AMSAT guys have discovered: it's hard to convince government agencies like Homeland Security to fund our launches in exchange for providing emergency communications of we can't demonstrate that we can build _reliable, consistent ground stations in reasonable numbers_. They aren't really interested in helping you learn about radio or to talk to your friend in New Zealand. They want a system for emergency communications. And if we want their money, we are gonna have to _make_ satellite communications easy.
Oh, and if we don't want their money? We aren't gonna get a launch. We can't hold enough bake sales to make it happen.
Probably to build about everyting by your self for a satellite for all like an HEO make you a real experimenter because if you are not succesfull you cannot send the equipment to the manufacturer but you are obliged to study your problem by your self looking and reasoning over your own schematic diagrams.
When OSCAR-10, OSCAR-13 and AO40 where alive and well we all were assisted in solving our technical problems by some well know teachers and radio scientists every day on this BB like James Miller G3RUH, Charles Suckling, G3WDG and Tom Clark W3IWI now K3IO but unfortunately they actually desappeared from this BB because they are not anymore interested to discuss about the technical level and matters actually seen on this BB.
I suspect they are very interested in such things. I have great admiration for all of these gentlemen. I first learned Tom Clark's name when I found his Totally Accurate Clock project (GPS and timekeeping are other interests of mine). James Miller's nifty Plan 13 paper led me to write my own satellite tracking code in Python, and I'm working on a nifty idea to extend it. I'm less familiar with Suckling's work, although I know he's a pretty familiar name in the microwave community.
I suspect that what each is not interested in (and, in case you hadn't figured it out, neither am I) is listening to a bunch of pointless, idiotic complaining. Amsat-bb is incredibly high noise to signal ratio. Complaining is a significant portion of that noise. It serves no purpose at all.
Read please into the AMSAT-BB archive and compare the importance of both technical and operating contents of messages at time in wich OSCAR-10 OSCAR-13 and AO40 were operational and I am sure that you will learn more and more about the purposes of the Satellite Amateur Radio for the benefit of your own skill.
It's not a bad suggestion, but it doesn't really justify the current level of complaining we see on the list today, does it? It would be great if AO-10, AO-13 and AO-40 were still in operation, and we had a platform upon which to explore the various modes and capabilities they had. But we don't. They are dead. And, barring an AO-7 like miracle, they aren't coming back. You seem to imply that because they are gone, there is nothing better for us to do than complain. I think otherwise.
For instance, here's a little thought experiment I've been running. I've been monitoring SEEDS telemetry. I've written a very simple tracking application that drives my little FT-817 to track the signal in doppler, and then just examine the telemetry. There are some interesting bits inside: notably the various voltages, the current produced by each of the six solar panels, and four different temperature measurements. I noticed that the temperature swings are fairly large depending on whether the satellite was illuminated or not. That's hardly a profound observation: it's rather obvious. But imagine you were designing a satellite, and wanted to know what the likely swings in temperature were, and how that effected both battery and solar panel performance. Well, that's a bit deeper question, and it requires some careful thought and (for those like me whose training isn't in spacecraft design) a bit of research. Phil Karn hinted at some of the differences between LEO sats and HEO sats regarding thermal control on the namaste-dev list which I found interesting.
I'm also _really_ anxious to hear how DELFI-C3 works out once it shifts over to open amateur use. I am interested in what can be done in these small form factor sats, and I think engineering a system which runs without batteries on purpose (as opposed to AO-7) is really intriguing.
That's what I'm having fun with. That's how _I_ am justifying my ham radio license and its mandate to self train. And I wouldn't have likely gotten here without the FM sats and cubesat launches. Indeed, without those launches, we wouldn't have much to listen to AT ALL. And, unless there is some news deep in the innermost chambers of the AMSAT leadership that we are unaware of, it doesn't seem to be the right time to start holding your breath for an HEO launch anytime soon.
Hell, you don't even need to know what Doppler is with these easy HEO satellites. If you want to take the easy way out though...
Every experimenter know what the Doppler is but if you like to make your life difficult with Doppler for a few minutes QSO having the time to only say.......Five.......Nine.......class.......class ! and then come into this BB asking for the call letter of the guy you suppose have made a QSO then it is better to stay with the FM satellites !
Sigh.
Luckily, I don't need to take your advice about what I should or shouldn't "stick with".
Mark KF6KYI
Mark KF6KYI
Best 73" de
i8CVS Domenico