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Re: P3D information




Hello Phil!

08 Oct 00 00:14, you wrote to All:

 PK> I absolutely agree, and that's just what makes the P3D Rudak subsystem
 PK> so interesting: it'll be the first amateur satellite with a real-time
 PK> digital repeater capability fast enough to support good quality
 PK> digital voice. Being able to do that with small portable antennas
 PK> should definitely interest a lot of hams.

This does sound interesting.  Looking forward to hearing more on it...


 PK> At some point it becomes much more expensive to maintain that old
 PK> investment than to start over with something new. I believe we passed
 PK> that point in AMSAT long ago.
 PK>
 PK> What baffles me the most is the accusation that I'm somehow an
 PK> "elitist" for advocating digital and microwave modes that require new
 PK> ground equipment and/or don't make full use of existing equipment.
 PK>
 PK> These people apparently do not consider it even slightly elitist to
 PK> insist on modes and bands that require expensive analog radios, high
 PK> power amplifiers and enormous amounts of aluminum that can only be
 PK> legally erected on a tiny minority of homes built in the last 25
 PK> years. These are modes that only a tiny fraction of radio amateurs
 PK> have ever used or will ever be able to use. Modes that have kept AMSAT
 PK> as a small niche of a hobby that is itself rapidly becoming irrelevant
 PK> because of similar attitudes.

There is a point there, and to some extent, I agree with you.

 PK> To be sure, they still wouldn't have gone anywhere had they not
 PK> developed the necessary digital receiving equipment and made it widely
 PK> available at reasonable prices. And so it is with digital and
 PK> microwave modes on amateur satellites.

I think the $64 question here is whether amateurs will develop the necessary
equipment.  I'm hoping there's enough experimental types around that will.
Unfortunately, I'm not equipped to go into design and development... but
construction of a moderately priced kit is something I would gladly do to run
these modes, and then I'd be pushing them to their limits in a portable
capacity. :-)

 PK> Every satellite system consists of two segments: the space segment and
 PK> the earth segment. Over the 20 years I've been involved (off and on)
 PK> with AMSAT, I've seen an enormous amount of work go into the space
 PK> segment. I have nothing but admiration for those who conceive, design,
 PK> build and operate amateur satellites. P3D is a technological tour de
 PK> force.  It's something that AMSAT can rightly be very proud of.

Indeed, no argument there.

 PK> One goal may be to enable as many radio amateurs as possible to
 PK> communicate directly by amateur satellite with the greatest
 PK> flexibility, highest quality and lowest overall cost -- this
 PK> being the sum of the earth segment and space segment costs.
 PK>
 PK> If this is your goal, then the case for moving to digital modes on
 PK> microwave frequencies becomes inescapable. So does the need to design
 PK> the necessary ground station equipment and make it inexpensive and
 PK> readily available.

Well, I can only speak for this end of the world.  At the moment, we are
already approaching a critical stage, with government spectrum policy becoming
hostile to anyone except those with big bucks, and seemingly little input into
the process.

We need something that will enable many amateurs to get onto satellites at low
cost, with good performance.  Digital modes are definitely the way to go.  As
for frequencies, I feel we need a range of frequencies from 1.2 GHz into the
tens of GHz.  The lower bands will be easier for aiming portable antennas, the
higher bands could offer better bandwidth, or perhaps a higher grade of comms,
whatever.

Whatever it is, we need to experiment, and we need to use those higher bands.

I'm just saying such a transition needs to be staged, but that can already be
accommodated by the lifetime of existing satellites and Phase 3D, which would
pick up the analog traffic, and we build some new digital birds.

Tony, VK3JED

.. re you reading THIS for?
--
|Fidonet:  Tony Langdon 3:633/284.18
|Internet: tlang@freeway.apana.org.au
|
| Standard disclaimer: The views of this user are strictly his own.


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