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Re: commutating antennas (was snip)



Well, it is a new thread, so I guess I can weigh in one more time.  I hate
to see myself disagreeing with Phil (because I have respect him for what he
has done and what he brings to the table).  Maybe I am the problem?  (I did
more snipping as well).


Rick wrote> >And I guess that pretty well defines the two sides which occupy
much of the conversation that goes on this BB.  There are those that are
looking mainly at optimum engineering solutions and those that want to try
to factor in less well defined political/people requirements.

Joe writes ->This makes little sense, no matter what we build we have to
factor in the political/people requirements.  I would argue they are the
most important requirements of all.  Who are we building this for?  I
thought it was for people.  Would the perfect computer have no user
interface?  I know the user slows my computer down greatly!

Phil wrote > Why do you think these are two "sides" here, somehow in
conflict?  Do you think that by calling for an "optimum engineering
solution", I'm proposing something counter to what most of the members want?

Joe writes ->The optimum solution factors in what the members want.  We all
bring our resources to the table.  We do it collectively (unpopular word
today).  Our leaders respond by applying our pooled resources to projects
they believe will best fit the needs and desires of the group.  If they go
too technical the masses vote them out, if they don't go tech enough the
best and brightest go elsewhere.  It is a tough line to walk.

<More Snipped>

Phil wrote > So what does a systems approach say about AMSAT's current
practices?
>
> 1. The use of inefficient analog modulation methods (CW, SSB & FM)
>    instead of modern digital methods results in substantially higher
>    system costs (especially on the spacecraft), substantially larger
>    ground and/or spacecraft antennas, substantially poorer
>    communications quality, and substantially lower capacity. They may
>    rule out certain promising spacecraft designs, e.g., the "switched
>    antenna array" we've been discussing, or an onboard digital
>    regenerator like RUDAK.

Joe writes ->The "inefficient methods" are what the users want and have
accepted.  Most of our established user base has zero system costs if we
stay with these modes.  Spacecraft costs are kept reasonable by orbiting a
simple "bent pipe" birds or straight forward transponders.  Forcing a new
unproven (in Amateur circles) digital mode is a bad idea for satellite use.
It is very possible we will wind up with a bird that only plays Beta tapes
or only drinks "new" Coke if you know what I mean.  The directors have taken
an excellent approach to this by piggybacking the new with old.  Let's see
how the new works before we bet the farm.

Phil wrote> 2. The use of low frequency bands (especially 2m) where
bandwidth is
>    severely limited and artificial and natural noise levels are high
>    also implies larger antennas, substantially higher system costs and
>    substantially lower system capacity and quality.

Joe writes ->Bandwidth and capacity have never been the problem.  Just
listen to the FO birds.  The two meter down link has inherent ADVANTAGES
(read Bob's post about how 2 meters means more signal).  Most of the noise
problems have left 2 meters, they have moved higher in the spectrum, I see
no good reason to move up there and fight them.  Antenna size is debatable,
look at the small, popular, and very easy to transport arrow.  It is much
easier to use and hide than my 3 foot dish.  Cost for the lower frequencies
are lower not higher.  The standard approach to S band is to build a mode B
station.  After doing that put even more time money and effort into add the
equipment required for S.

Phil wrote> 3. A requirement for large antennas keeps away many prospective
>    satellite operators. Sure, you can work an "easysat" with a small
>    hand-held antenna. But the mere fact that they are *called*
>    "easysats" shows that we have a real problem with the satellites
>    that *aren't* "easysats".

Joe writes ->The lower frequencies win out here again.  If people want to
get their feet wet in satellites this is the way to go.  Most amateurs like
the prospect antennas they can actually build with a hacksaw and a tape
measure, not a metal lathe and a milling machine.  The evidence is strong
the upper limit for this is "S" band.  Look at the gyrations we have gone
through trying to build decent feeds for reflectors at 2.4 Ghz.  Most of
these when tested with "real" equipment have been shown to be poor
performers.  Most of the people who have put any real time and effort into
the easysats have found them to indeed be easy sats.

Phil wrote> The conclusions are obvious. If AMSAT is ever to significantly
improve
> the quality of its satellite systems, reduce its costs, and attract
> more users, it has *no choice* but to adopt more efficient digital
> modulation schemes and move up to the microwave bands. This isn't just
> an optimum engineering solution. It's what we *must* do to survive.
>
Joe writes ->This conclusions implies we will attract more users by giving
them more hoops to jump through before they can operate via satellite.  I
don't get it.  (To twist "Field of Dreams") Make it more complicated, and
difficult to understand as well as do and they will come.

Phil wrote> Yes, this requires new ground station equipment that we don't
have
> now. But why is that so terrible? AMSAT appears poised to spend
> several million dollars to design, build and launch a major new
> satellite or two. If so, shouldn't AMSAT and its members also be
> willing to spend some small fraction of that amount to design, build
> and manufacture new ground station equipment that could
> *substantially* reduce the cost of these new satellites, increase the
> quality of the service they provide, and permit many hams currently
> limited by space restrictions or CC&Rs to join AMSAT and use the
> satellites?
>
Joe writes ->Shouldn't AMSAT do what their members want it to do?  Most of
us already have a significant investment in our stations, and do not want to
see them obsoleted.  If you are arguing we will add this new equipment to
our existing stations I believe you are scarring away even more potential
users through increased complexity and cost.

AMSAT-NA's board has made some good decisions of late in making an effort to
give the members what they want, as well as upholding the long held
tradition of providing room for experimentation on the birds.  Let's check
out the new modes, they can make some neat secondary payloads.  Let's not
abandon or existing proven modes just yet.

My Opinion,
Joe
ka0yos@amsat.org

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