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Re: WEFAX Info (OT)



The "current high-speed system" is the actual data from the imager on the 
satellite. Meant to be processed by a LARGE groundstation.  Not meant for 
general consumption, but not encrypted either for the experimenter.

The WEFAX feed is processed by a ground station and re-transmitted.  The 
low-speed feed proposed is simply a replacement for the analog FAX that is 
currently transmitted.  Apparently the analog feed is an "exception" to 
normal internationally agreed upon power-density specs for satellites in 
that frequency range.  The digital system with FEC will allow them to drop 
the WEFAX transponder's power output to the "standard" while still improving 
the system.

This is all availble on NOAA's site if you search for it.  For the rest of 
the world, I've read that the Meteosats are going to do the same sort of 
thing, but I do not know if it'll be compatible with the American system.  
(Weather equivalent of SECAM?  Standard Essentially Contrary to the American 
Method?  Who knows.. got to stick a joke in this e-mail tho!!!)

Fred W0FMS

>From: Howie DeFelice <hdefelice@petrexintl.com>
>Reply-To: Howie DeFelice <hdefelice@petrexintl.com>
>To: "Frederick M. Spinner" <fspinner@hotmail.com>
>Subject: Re: [amsat-bb] WEFAX Info (OT)
>Date: Thu, 20 Jun 2002 10:30:09 -0400
>
>Thanks Fred, that would be cool. There shouldn't be too much of a problem
>converting the MMDS downconverters, provided that the VCO will pull that
>far. The Motorola synthesizer chip most of them use works down to around 
>500
>MHz. I'm glad the new system will use FEC. The current high speed system is
>ridiculous, 2.1111 MBPS BPSK with no FEC requires 10-12 dB of Eb/N0 to
>decode. Most every other commercial system is about 6 dB better using 1/2
>rate FEC. Good luck on the move and have fun at field day !
>
>Howie AB2S
>
>----- Original Message -----
>From: "Frederick M. Spinner" <fspinner@hotmail.com>
>To: <hdefelice@petrexintl.com>
>Sent: Thursday, June 20, 2002 9:07 AM
>Subject: Re: [amsat-bb] WEFAX Info (OT)
>
>
> > Well, after I complete my move to the country in a month or two, I'll
> > probably try this setup.  I built and tuned up (on a network analyzer at
> > work) the 1691 linear patch last September!
> >
> > I suspect it will work a little better than a "coffee-can" type feed, 
>but
> > the coffee-cans worked quite well.
> >
> > I've often thought that some of the commercial TV downconverters we are
> > playing with for AO-40 could be reconfigured to 1691 MHz.  Or at least
> > provide the 1553.5/1828.5 MHz LO (or other freqs with ham gear
> > or modified scanners) --  some day I'll need to try modifying a Cal Amp 
>or
> > other suitable downconverter.  When the fully digital stream
> > comes on it will be a super cool setup as it will basically by the 
>entire
> > NWS alert and graphics feed.  Again, supposedly this will be all
>unencrypted
> > and the plans for the demodulator will be public.
> >
> > I'll measure the beast (1691 patch) w/a caliper this weekend and send 
>you
> > dimensions if you are interested.  I've not put a choke ring around this
> > design, and that is something else to try.
> >
> > Fred W0FMS
> > >From: Howie DeFelice <hdefelice@petrexintl.com>
> > >Reply-To: Howie DeFelice <hdefelice@petrexintl.com>
> > >To: "Frederick M. Spinner" <fspinner@hotmail.com>
> > >Subject: Re: [amsat-bb] WEFAX Info (OT)
> > >Date: Wed, 19 Jun 2002 15:10:47 -0400
> > >
> > >Hi Fred,
> > >
> > >I recently experimented receiveing GOES-10 at 1691 MHz. I was supplying
> > >some
> > >equipment to Lockheed-Martin for demodulating the high speed digital
> > >downlink. I wanted to test the equipment before I shipped it, so I used 
>a
> > >DEMI low noise amplifier connected to a "coffee can" feed mad from a
>piece
> > >of galvanized air duct with a feed probe. I placed this in front of a
> > >Prodelin 1.2M offset antenna on the roof. I used the audio demod out of
>the
> > >HP spectrum analyser into a sound card. I was amazed at being able to
> > >actually decode pictures with this setup. It was allot of fun. I had
> > >thought
> > >about a patch feed, but didn't have that much time to play. I would be
> > >interested in your results.
> > >
> > >Regards,
> > >Howie AB2S
> >
> >
> >
> >
> > <html></html>
> >
> >
> > _________________________________________________________________
> > MSN Photos is the easiest way to share and print your photos:
> > http://photos.msn.com/support/worldwide.aspx
> >
> >
>




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