[amsat-bb] Re: LEO's
kf6kyi at gmail.com
Wed Jun 18 20:07:47 PDT 2008
On Jun 18, 2008, at 5:38 PM, i8cvs wrote:
> ----- Original Message -----
> From: "Mark Vandewettering" <kf6kyi at gmail.com>
> To: "AMSAT-BB" <amsat-bb at 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
>>> 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
>>> 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
> 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
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
> 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
> 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
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
> 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
> 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
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
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
> life difficult with Doppler for a few minutes QSO having the time to
> say.......Five.......Nine.......class.......class !
> and then come into this BB asking for the call letter of the guy you
> have made a QSO then it is better to stay with the FM satellites !
Luckily, I don't need to take your advice about what I should or
shouldn't "stick with".
>> Mark KF6KYI
> Best 73" de
> i8CVS Domenico
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