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wxtoimg



Hello Ghena,
 The Wxtoimg program is operating very well indeed here at my qth,
Whakatane New Zealand.  However you will need the following items to
receive the signals. The program itself is designed to use the sound card
connected directly to the receiver, and I would not recommend recording
the signal first and then trying to decode it as most tape systems do not
have sufficient speed stability for the program to decode.

1. In my experience the most important item is the antenna. Having tried a
bewildering variety of types my recommendation is the Quadrifiliar type.
The best of these, in my opinion, is the Tall Narrow Quad
http://www.pilotltd.net/qha.htm . Build one of these, although the article
calls for 3/8" copper tube for the elements I have successfully used 5mm
copper wire and number 8 gauge galvanized fence wire for the elements.(An
old NZ joke, so I had to try!) Probably not optimum but they both work
fine. The only point to watch is to get the "twist" correct... they won't
work if this is wrong. I tried!

2. Depending on the receiver and coax length you may need a preamp. Almost
any 2 meter design can be persuaded to work at 137 Mhz. I use a long (50
feet) run of coax and a ubc 3000 scanner (unmodified) and find things are
much better with the preamp, and better again with the preamp mounted at
the antenna. The preamp is the dual gate mosfet design from the arrl hand
book built dead bug style, and tuned up on the sat signal itself.

3. With these two items out of the way the next pitfall is the interface.
 Since I donít know what you are using for a receiver this can only be a
general observation. If possible run the recv on a battery supply to start
with... some set ups can produce severe hum due to, I guess, ground loops
between the recv and the computer. Once things are working you could try
the sets own power supply. Make up a shielded cable to run from the recv
external speaker socket to the computer "line in" port on the sound card.
If the computer is not well shielded keep the recv well away from it. You
can test this aspect by turning the recv on, using its own speaker, tuned
to 137.620 for NOAA 17 with the antenna and preamp connected. Listen to
the noise level and then turn your computer on. There should be very
little increase in the noise level. If there is try moving the
recvr,preamp, antenna further away from the computer. Some older monitors
are also notoriously "noisy" as well.

 Once you are happy with this aspect and can hear the sat signal clearly
as it passes over you can set up the program. This is pretty well set out
in the supplied help files, but there are a couple of points to watch out
for.
This assumes you are using some version of Windows. The Linux gurus can
probably help you if you are using the linux version.
 The mixer must be set up to use the "line in" volume slider. I have found
about 1/2 to 2/3 on the slider ok. Most importantly turn off ALL other
recording inputs (mute them). This is essential since a lot of computers
have a built in microphone and this causes havoc if it is not muted.
 Start the program, and check to see if you can hear the sound from the
recvr through the computer speaker.
Set up the computer clock accurately. Use an internet time server if
possible. Get a current set of keplerian elements. The program will do
this for you if you connect to the internet and use the "update keplers"
options from the "file" menu. Under the satellite menu set up use the
"auto detect apt" option.
 Depending on a great many things, it would pay to disable any screen
savers, and any other background programs, leaving just windows and
wxtoing running then leave the system running. The program will wait for
the next active satellite pass and record it as a wav file. If the
computer is reasonably fast it can display the pic as it receives it.
"reasonably fast" means over 300Mhz Pentium in my experience. A 166 Mhz
Pentium with mmx and 64 Mb memory wouldn't work for me, but would record
and then decode.
 After receiving your first file you then have to go to the help menu and
follow the instructions for slant correction etc.
 The "vol" level at the bottom right of the screen is important, I try to
keep this at about 70 on the display.
 Most of the above is in the help system, but it can be a little confusing
when nothing seems to work properly at the start!
Since I have almost certainly forgotten something do not hesitate to
contact me, I'm sure you will be very impressed when the program is
working. It is certainly the best I have tried.
By the way I have no connection with the program or its' author(s).
         Cheers,
                Don
                ZL1THO. 


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