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Re: OT - Weather satellite antennas



Ed Tump wrote:
> Folks,
>
> Thanks for the response on power. Now I wonder if my Arrow satellite antenna
> will work for these weather satellites or my AL800 HT antenna.
>
> Any ideas?
>
> Thanks.
>
> 73,
>
> Ed
>
> KC9GWK
> Grid EN52
>
> AmSat Member
>
>   
I've done a bit of work recording the NOAA satellites, using the 
wideband FM settings on my little Yaesu VX-3R, or the Wide FM mode on my 
Radio Shack Pro-60 hand scanner and tracking it by hand with my Arrow 
antenna.  The arrow definitely provides significant gain around 137 Mhz, 
and I am able to get fairly clear recordings.  The major problem isn't 
actually antenna gain, but the filter bandwidth of the receivers.  Wide 
FM is actually way too wide: the satellite actually uses about 50khz 
bandwidth, and the Wide FM filter bandwidth is more like 200khz, which 
means two things: you get about six db more noise, and you can get 
interference from other sources, such as other satellites.  For 
instance, I blogged about this a while ago:

http://brainwagon.org/2008/02/09/saturday-noaa-17-pass/

On this pass, I actually used a small preamp, which really doesn't help 
with my setup (handheld yagi means coax losses are low).  I wrote my 
own  apt decoder, which still had some bugs in this incarnation, so  you 
can see that I lost sync a couple of times.  The  bright  rectangle of 
noise overlayed is probably  an Orbcomm satellite operating  on a nearby 
frequency: a  weather receiver with smaller frequency bandwidth would be 
helpful.

You might ask what you can do with just the normal narrow fm rece[topm 
pf upir average HT.  I did that experiment too.

http://brainwagon.org/2007/12/16/narrow-versus-wide-fm/
http://brainwagon.org/wp-content/uploads/2007/12/test.jpg

You can see all sorts of clipping artifacts at the beginning where the 
receiver is set in narrow mode.  In particular, you can't actually 
reproduce the nice stepped gradient that appears between the images.  In 
wide band, we get much better dynamic range.

If you nose around my blog, perhaps searching for noaa, you can find 
other pictures that I did.   All of these were recorded on my Macbook 
using Audacity, fed from my Pro-60 or my VX-3R wired to my dual band 
Arrow antenna, and then decoded with my own software.

Feel free to hit me with email if you have any further questions:

    Mark KF6KYI


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