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Re: Satellite Modems on HAM bands?




How about DVB/IP?  DVB-S/IP cards are going for $35 on e-bay, and $100 new 
for the receive side.  Several groups in Europe are making modulators now.  
The modulation type most commonly used is QPSK, which is probably more 
realistic for radio use.  Some of the European boards are also experimenting 
with DVB-T and ATSC 8VSB formats.

The nice thing about this is that symbol rates down to 1 Msps are possible, 
so you wouldn't need to take up 27 MHz+ of ham spectrum on your links.  No 
these are not SS like 802.11 but there are many cases this could be an 
aadvantage.. Don't understand why anyone isn't persuing this.

Especially the ATVers -- DVB-S receivers can be had new now for well less 
than $150 for the low end consumer boxes.  And the IF tunes 950-2150, so 
it'd be trivial for 1240 MHZ and simple for 902 and 2400 MHz converters...

By the way, I live in the country and my one-way sat internet uses 
DVB-S/IP....Ku band...

Fred W0FMS


>From: Bob Bruninga <bruninga@usna.edu>
>To: amsat-bb@AMSAT.Org, TAPR APRS SIG <aprssig@lists.tapr.org>
>Subject: [amsat-bb] Cable Modems on HAM bands?
>Date: Thu, 15 May 2003 16:43:35 -0400 (EDT)
>
>A Cable Modem operates at RF (in a cable TV system).
>
>WHy not simply hook it up to a converter to up/down convert the signal to
>a pair of HAM bands and get High data rates on the HAM bands.
>
>This idea came from Ron Parise WA4SIR during a chat around the water
>cooler.  There's lots we don't know, and maybe someone on the APRS or
>AMSAT sigs works in the industry and can fill us in.
>
>Things we assume:
>1) Uplink is below 50 MHz, downlink is somewhere in the CATV passband.
>2) Since uplink and donwlink are different, then a "repeater" would need
>to be installed in the city to tie everyone togther (or a HAM satellite).
>
>This approach at taking a consumer item and modifying it for HAM use has a
>certain atttraction, since it gives us an unlimited supply of
>cheap hardware on which to build...  The ONLY thing we have to build are
>the repeaters (or satellite), for all of use users its plug-n-play.
>
>Any experts want to fill in the modem details and the bandwidths and
>frequencies?
>
>Bob
>
>Since the uplink (inlink) is low data rate, it could probably fit easily
>in the 220 or 440 band somewhere, the downlink (or outlink) might fit in
>900 or 1296 somewhere...?
>
>
>----
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