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Re: Mir, SO-35, RS-18 stuff.



Good morning Steve,

MR STEPHEN G THOMPSON wrote:
> For
> years I've thought that the amateur satellite operating
> community was a little more sophisticated.......

I think by in large the satellite amateur community is the best of the
amateur lot.  There has been a great deal of anticipation associated
with commissioning of a new satellite, and the infrequent availability
only served to heighten this anticipation.  Many, many operators were at
the wheel yesterday looking for that parking spot.

I don't have a data sheet for this particular bird, but I was able to
listen quite a bit yesterday, :-) and there are some dynamics at work
which we don't see on the only other available FM bird, AO-27.

Hans, ZS5AKV, gave us an early indicator of the width of the receiver
aboard Sunsat by stating you should set your uplink 436.286 for the
first half of the pass.  Doppler on this bird will be somewhat greater
than 10 kHz.  If the center of the receiver passband is 436.291, Hans'
instruction tell us the receiver passband is exceptionally wide.

Design engineers apparently designed the passband intentionally wide to
make the doppler compensation on the uplink less critical for the
terrestrial user.  While on a mode J bird like Oscar 27, we tune
regularly to keep the 70 cm downlink centered in OUR receiver passband,
the Sunsat scheme serves the HT user well on a mode B bird.  However,
there is a definite disadvantage to having a wide open receiver,
especially if many operators are vying for air time.

Let's use a real world analogy. (can you tell I like them?)  Many people
are waiting at the gate for the opening game of the World Series.  At
the main gate, gate J, the attendants open the gate just wide enough to
allow 2 people to enter at a time.  The staff is able to examine tickets
(ACG circuitry), and allow those holding valid tickets (properly
centered, coherent, modulated signal) to enter.  At gate B,
unfortunately, a fairly new staff opened the gate twice as wide as the
staff at gate J.  Now, several fans can enter at the same time.  It is
much harder for the staff (AGC circuitry) to determine which people
(signals) are ticket holders (properly centered, coherent, modulated
signal), and which fans are "crashing" the gate (noise).  Civility and
order rule at gate J, while chaos and disorder dominate gate B.

Please understand I am not saying that mode J is better than mode B, or
that a wide passband is not a good idea.  In fact, the design of this
bird may be a good model for future easy sats, with some design
modifications, including tone access.  What I was trying to demonstrate
with my little analogy is that the dynamics of a wide 
receiver passband will cause the satellite to operate in a manner
different to our previous experience.  A wider gate allows more signal
in at once, and the radio circuitry must work harder to discriminate
between signals and for one particular signal to "capture" the bird.

> By the way,  you might rethink what you said about
> rights.  Nobody has any right to the use of amateur
> spectrum, myself included and it can be taken away,
> just like that.  At this rate it will be.

Of course you are right.  I meant that amongst the ranks of duly
licensed, suitably equipped operators waiting for their chance, ALL have
the same right to the bird.  Many operators attempting to access the
same bird at the same time sounds a lot like what we were hearing during
most of the Eastern pass yesterday.  I can't comment about the western
pass, the eastern part of the country wasn't in the footprint.  

Let's put more birds in orbit, and decrease the stress on the available
resources.  Easy sats similar to this bird would help swell our ranks,
and bring satellite technology world wide to the amateur community.  

73, Mike

                                       __\/__ 
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   |||   | |   * Mike Gilchrist - KF4FDJ ..... AMSAT Area Coordinator *
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 |  P  | |f|   * I.S. Professional ..... CNA .... Computer Consultant *
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