Re: Weather Sat Reception with a Scanner

"Pedro Motilla" . . . wrote . . .
> Does anybody has practical knowledge of receiving sat images with a "normal"
> scanner, normal I mean with a FM Narrow for radio amateur transmisions or a
> FM Wide for commercial FM Broadcast?
> 
> I found a lot of web sites were people says it is possible, but also found
> sites where people says that is not possible, that you need a rcvr with 50
> KHz band wide.
> 
> I tried with my scanner and results were certainly disapointing as I could
> not get a minimum quality printing.
> 
> It is the receiver or could be the software?
> 
> I use a Quadrifilar Helix for receiving and signal IS 9+.
> 
> Thanks.
> 
> Pedro

......................
Pedro,
A scanner can be used to receive weather satellite images.  I have
made many weather satellite images using a Uniden Bearcat BC80XLT
scanner.  I also receive normal 2 meter ham communication with that
scanner.

My first antenna was a cheap homemade ground plane antenna (about $8
and made out of 5 welding rods and a SO-239).  But it has to be
pointed at the satellite manually when the satellite is out of the
antenna pattern (e.g. 50 degrees in elevation or below about 20
degrees).  My present antenna is a homemade crossed dipole antenna
with gamma feed, reflectors, and phasing array.  It works very good
except when the satellite is below 20 degrees elevation, then I just
point the antenna at the satellite.  (For a near pass, otherwise, if
the satellite is passing far to the east or west of me, then I point
the antenna.)  BTW, I made that antenna 22 years ago and just got
around to using it.

I record the audio using the computer sound card and save it as a WAV
file.  I then process the WAV file using my own homemade demodulation
program.  Next, I used a graphics program (ULead) to do cropping of
the visible and the infrared images and did histogram equalization if
necessary.

I have since been using WXsat instead of my own program.  By the way,
I get good color images using WXsat.


Since you described your image as having " . . . minimum quality
printing", let me ask the following questions:

- What program are you using to demodulate the audio?  (If it is your
own program, you should test it with some NOAA weather satellite audio
that you can download from the internet.  Otherwise, you may want to
use a program from the internet.  WXsat works great and is free.)
- Are you using the sound card to digitize the audio?  If so, what
sample rate are you using?  (Otherwise, the demodulation algorithm
will not work right.  I use 11025 Hz, mono, and  8 bits to create WAV
files for WXsat to process.  I used a different sample rate with my
own demodulation program, but I used that different sample  rate in
the demodulation algorithm.)
- What does your image look like?  Can you see any features at all? 
Is it partially noisy?  Is it completely noisy?
- How do you know the satellite is passing by?  What satellite
prediction program are you using?  (I use WXtrack which is also free. 
I have done my own orbit predictions, but this is much easier.)
- What does the scanner audio sound like?  A good satellite signal
will sound like the "tick tock" of a clock when it is overhead.
- What kind of environment are you in?  Are there lots of steel and
metal around (e.g. faraday shields)?
- What frequency are you setting your receiver to?  NOAA 15 is 137.500
and NOAA 17 is 137.620 MHz.
- Finally, what satellites are you trying to receive.  Try NOAA 15 and
17.  NOAA 12 recently went off the air for a few weeks.

One of these days, I will get around to getting or building a receiver
with a wider bandwidth.  But for now, I am using my inexpensive
homemade weather satellite system to study satellite image
interpretation.  BTW, I recently got two good books on that subject: 
Berman and Conway.  Berman uses polar orbiting images while Conway
uses GEOS images.

Don't give up because it can be done,
Ken