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Re: WEFAX Info (OT)



To AMSAT-BBers:  I'm sending this slightly off topic reply to see if there 
is interest in me "web-publishing" the dimensions of my (untested on an 
actual dish) 1691 MHz patch feed.  Please ignore and accept my condolences 
if you are not interested.


The WXSATS are linear polarization.  I've used the ubiquitous "coffee can 
feed" and even three element "loop yagis" as feeds.

I've recently built a linear square patch antenna, tuned it up on a network 
analyzer, but have yet to hook it to the preamp/downconverter for 1691 MHz.  
I used to really be into WEFAX, but my interest wained a bit now that all 
that data is available on the Internet.  Still have the equipment and will 
eventually try it.  (OK, covenants have also killed off my permanent WEFAX 
setup.-- but not for much longer!)

If you really are interested I'll measure the dimensions of my square patch 
(a little rectangular after tuning) feed.  I used to use 4-5 foot dishes 
with a system of about 1 dB NF for really good WEFAX. Note: you will need to 
physically rotate either the feed or the entire dish to get the strongest 
signals on the WEFAX birds.  They are linear polarized and neither 
Horizontal nor Vertical in my experience.

Note: with the launch of the next gen GOES, the WEFAX is going to go away-- 
become all digital, anyway.  The specs are supposedly going to be public and 
the signals are to be unencrypted so this could be a cool new project in a 
couple of years.

There is already a 9600 GMSK subcarrier on the 1691 MHz transponder for 
EMWIN transmissions.  This too will go away.  All the data will be muxed on 
a higher speed FEC'ed data stream.  But this will likely take two-three more 
years.

Second note:  The WEFAX 2400 Hz AM Audio subcarrier is modulated on an FM 
carrier at about 50 KHz bandwidth.  A standard ham rig is too narrow on NBFM 
and too wide on WBFM settings to receive this signal.  So a cheap, 
appropriate reciever for this can be made by removing the second IF (455 
KHz) filter in a "Bearcat-like" scanner (replace with a 0.01-0.1 uf cap).  
This has worked in almost all cases and still allows the scanner to be used 
for other things (albeit at a wider bandwidth).

I'm assuming that you are going to use the WXSAT soundcard software to 
demod.  I played with it and it seems to work just fine given good IF 
bandwidth.

Hope this helps you, Jerry, and others on the amsat-bb list.

Fred Spinner, W0FMS

>From: "Gerald Payton" <n5gpc@earthlink.net>
>To: "AMSAT-BB" <amsat-bb@AMSAT.Org>
>Subject: [amsat-bb] WEFAX Info
>Date: Tue, 18 Jun 2002 23:12:18 -0500
>
>I apologize to the group for asking about weather satellite info, but my
>searching on the net has been non-productive.
>
>Specifically, I am looking for URLs or info on Geosats 1691 MHz antennas,
>feeds and such.  I have everything but the antenna.  I have an extra dish
>and would like to use it.
>
>Any help would be appreciated.
>
>Jerry  N5GPC
>
>
>----
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org




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