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PA2AGA > TCPDIG 24.10.96 00:49l 128 Lines 4629 Bytes #-10845 (0) @ EU
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Subject: TCP-Group Digest 96/224A
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TCP-Group Digest Tue, 22 Oct 96 Volume 96 : Issue 224
Today's Topics:
2300 MHz band reallocated (5 msgs)
IP for San Marino Republic ??
wampes on FreeSCO
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----------------------------------------------------------------------
Date: Mon, 21 Oct 1996 12:24:37 -0700 (PDT)
From: Phil Karn <karn@qualcomm.com>
Subject: 2300 MHz band reallocated
>> Efficient digital modes favor a higher bandwidth/power ratio than these
>> transponders can support. Sigh.
> Hmm.. Phase-5 has a bit too long delay roundtrips, however more
> Phase-3s, and perhaps Phase-4s will be made. Microsats propably
> can't do it.
I don't understand this comment. Round trip delay can affect protocols,
but it is independent of the RF link calculations.
The microsats are *very* inefficient in their downlinks. They have
enough downlink power to support megabit data rates (with typical
Oscar antennas and proper FEC, and assuming sufficient spectrum) but
they have trouble running at even a kilobit because of a series of bad
system design choices.
Phil
------------------------------
Date: Mon, 21 Oct 1996 22:11:35 +0200 (EET)
From: Matti E Aarnio <mea@mea.cc.utu.fi>
Subject: 2300 MHz band reallocated
....
> So it would have been very nice to go even faster, which means wider.
> While the room may not be available on 70cm, and as you say the HELAPS
> amplifiers may not handle a wider bandwidth, how about putting in a
> direct path from RUDAK to the 10 GHz TWTA (or possibly 24 GHz)
> downlink that runs even faster?
At this late of design, I m afraid not.
(How is your German ? http://www.aball.de/~pg/amsat/rudak.htm )
Separate wider IF feed from RUDAK could be added - perhaps.
People have been known to make last-minute fixes at Oscars
almoast when up at the launcher :-)
If you can pressure RUDAK-team to provide the signal, AND
get an ok from Karl Mainzer, I can perhaps push our team to
make the necessary last-minute modifications... (if any)
I am uncertain as to how wide the IF-matrix really is, all
that needs widening is the injection from RUDAK to IF, if
it is made smartly. The IF is 10.7 MHz, and it uses commodity
(BC) filters, which may be a bit narrow..
Anyway the IF-matrix is capable of feeding 1-3 inputs to each
transmitter, and signal is preconditioned when it comes from
inputs to the IF-matrix (as far as I know).
> Phil
/Matti Aarnio -- going home for tonight..
------------------------------
Date: Mon, 21 Oct 1996 12:40:00 -0700 (PDT)
From: Phil Karn <karn@qualcomm.com>
Subject: 2300 MHz band reallocated
>>It's a pity that the current AMSAT project is so bandwidth-limited.
>> - Brian
>No doubt! As far as I can see, our best bet to see reasonably rapid
>improvement would be to "get behind" the current SSTO RLV technology, and
>push HARD.
I don't follow. I was trying to make the point that the capacity of
AMSAT satellites could be greatly increased through better system
engineering and the use of more modern technology, *without*
increasing spacecraft size or mass. It would require new equipment on
the ground, but the price of this sort of stuff is dropping rapidly.
We hams have in the past rightly prided ourselves on being clever and
applying brains instead of brawn ($) to our designs. AMSAT's past
accomplishments along these lines are legendary -- using B&W painted
tape measure rules for antennas that double as solar spinners,
To be continued in digest: tcp_96_224B
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