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Re: (forw) Ham operators will get to help NASA with space experiment



Hi Jeff and others interested on the mailing list,

At 05:56 AM 11/04/1999 -0500, Jeff Davis wrote:
>----- Forwarded message from NASA Science News
<expressnews@sslab.msfc.nasa.gov> -----
>
>NASA Space Science News for November 4, 1999
>
>Last flight for veteran will boost new propulsion concept: Ham radio
>operators can help NASA collect and analyze data from a satellite
>scheduled for launch Nov. 19. Data from the Plasma Experiment Satellite

I would like to add a few notes on receiving data from JAWSAT.

Modems:
	   JAWSAT has two GMSK modems. One is fixed at 9k6 (9600 bps)
	   for transmit and receive. The other can be set to 9k6, 19k2,
	   or 38k4. The receivers connected to the modems have their
	   bandwidth set for 9k6 only.

	   You can use a G3RUH modem but you may have a 3 db hit in
	   performance. I have not found any "Ham" modems in the USA that use
	   GMSK. If you know of any please let me know and so we can pass
	   it along.  I have purchased a GMSK modem kit from England.
	   Check out http://www.gmskdata.co.uk/index.html for one source.

	   We will try to use 9k6 and 38k4 only until someone comes up
	   with a modem that can be easily switched between three receive
	   data rates.  If you think we should be using 19k2 let me know. I feel
	   that if I have to changes filters on my radio I would go for 38k4
	   anyway so I can receive UO-36.

Radios:
	   Any radio/modem being used on the current 9k6 satellites (Ko-23,UO-32 etc)
	   can be used to transmit to JAWSAT (9k6) and to receive at 9k6. For the
19k2
	   and 38k4 data rates we have been using a ICOM PCR-1000 receiver for
	   testing on the ground.  It will work for 38k4 but its wide FM 50 kHz
	   filter limits it performance.  I was able to receive UO-36 38k4 beacon
          packets using a PC-1000, a PacComm Spirit-2 TNC (Satellite Model), a
          Landwehr preamp and a KLM 40CX antenna.

	   We have purchased cards for out FT-736 and IC-821 radios that
	   will let them work at 38k4.  See http://symek.com/sat/main.htm
	   for information on the IFD, wideband FM highspeed data 
	   receiver/demodulator card.

Antennas:
	   The link calculation I ran last night shows that the 1.6 watt 437.070 Mhz
	   transmitter with a 1/4 wave antenna could send 38k4 data and be received
	   on the larger 70 cm OSCAR antennas (14 db or more).  The 2 watt 2403.2 Mhz
	   transmitter with another vertical antenna and sending at 38k4 could be
	   received with a 24 db antenna. We can adjust the RF power on the
437.175 Mhz
	   transmitter from 0 to 8 watts. Running it at the highest power would allow
	   38k4 to be received by any antenna currently receiving the other 9k6
birds.

Data format:

	   We are still working on the final data formats to be used for sending down
	   the PEST data.  The data is saved in 8 megs of a RAM disk. So far we have
	   been down loading the RAM disk a packet at a time. The data formats can be
	   found at http://www.xmission.com/~kohlwey/jawsat.html.  Updates will done
	   to that web page first.

Other modes:

	   If the power budget allows it we may also have an analog FM "bent pipe" on
	   while we are taking data. If the launch happens in the morning this is
more
	   likely to happen because we can use the 437.175 transmitter running at low
	   power.

Long term operation:

	   In the long term I would expect the JAWSAT to be mostly in analog and not
	   digital.

Contacts:

	   If you would like to help or need more information feel free to E-Mail me
	   at n7sfi@amsat.org  or  Paul at kc7qfs@amsat.org


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