[amsat-bb] Re: Highest data rate achieved in the Amateur Satellite Service
GW1FKY at aol.com
Thu Dec 2 03:23:00 PST 2010
You are quite correct 48K data rates have been used on amateur satellites.
I trust that it is OK with Mark Hammond but here is a copy of a recent
posing on the BBS regarding experiments to be carried out on AO -51.
James Miller was I recall very involved in the use of higher data rate
exchange and you might find some information posted on this. Another good
source are the listings of the operational frequencies and modes
of operation that are posted on a number of well known web sites including
The main problem and concern of course is the need to modify equipment to
be able cope with these higher
rates. As you state modems are available but the inclusion in the
equipment can be quite costly and i am not sure about the validity of warranty if
you do make these additions.
Another concern is that with the LEO's tracking and the doppler shift are
a very significant factor , however
with such short pass times of course the higher rate of date exchange is a
very valuable asset especially
Ken de GW1FKY
Just a reminder that we'll be running a few days of 38k4 packet
beginning Sunday afternoon/evening until Thursday afternoon/evening,
as per the schedule below. Note the voice repeater will be OFF.
Please keep in mind that receiving packet at 38k4 requires more than
your "stock" FM receiver and TNC. Generally speaking, folks are using
a Symek board installed in their satellite radio to tap the IF which
is then fed to a high speed TNC. Other options for a receiver include
a PCR-1000/1500/2500 in FM mode with filters set to 50 kHz (NOT
Wide-FM) (I think that's the right filter width).
Please remember Douglas Quagliana's KA2UPW soundcard decoder (as
presented in the AMSAT Journal a few issues back) that can be
downloaded here: http://www.quagliana.com/ Look for Willow and
Sabins. I suggest you get the software and test it out at 9600
before you attempt 38,400, so to become familiar with how it works
with your receiver. It does work at 38k4--but remember you must have
an appropriate receiver!
It is possible to use some of the SDR stuff I'm sure, if you record
with your SDR software and play back through KA2UPW's Willow program.
I have a few options in my shack, as I've been running 38k4 since the
good old UoSat days:
Receivers capable of 38k4 (up to 76k, actually):
TS-2000x with Symek IF board
TS-790A with Symek IF board
Paccomm Spirit/Sprint-2 Satellite TNC models with 38k4 filters installed
My preferred combination is the TS-2000x with Symek IF board feeding a
Pacomm Sprint-2 satellite model. I seem to get the best performance
out of this combo.
Here's a reminder of the schedule:
November 14 (late UTC)
38k4 Baud PBBS Operations, L/U
Uplink: 1268.705 MHz FM at 9600 baud
Downlink: 435.150 MHz FM at 38,400 baud
November 18 (late UTC)
FM Repeater, L/SU
Uplink: 1268.705 MHz FM (no PL tone)
Downlinks: 2401.200 MHz FM *and* 435.300 MHz FM (at low power!)
Mark L. Hammond [N8MH]
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