Currently there are 4 NOAA APT weather satellites in operation the
latest being NOAA 19 launched on the 6th February 2009.
NOAA 17 developed a serious fault in February 2010.
The fault resulted in badly degraded images which then impacted composites built using them. For this reason I
took the decision to cease recording of NOAA 17 images entirely however release 2.10.7 of WXtoImg provided the option
of excluding specific satellites from composite images so this option was used instead.
From May 8 2010 most NOAA 17 passes produced good images with only the occasional poor one but I don't recall seeing a good one lately so I am using the WXtoImg 2.10.11 option to exclude in from the web pages.
The NOAA POES status page should carry the latest information.
All the satellites are in approximately circular polar orbits at around 850km altitude
and transmit 10w RF in the 137-138MHz band which makes them relatively easy to receive with a simple antenna.
The main problem with reception in the UK is the staggeringly stupid decision to allow text pagers to operate in the same band. Pager interference will
be seen on most of the pictures as short dark lines where a pager signal wiped out the satellite.
The demodulated signal is processed through a normal PC soundcard and the two greyscale images at different infrared wavelengths combined
to produced the false colour images displayed below.
The MCIR-precip composite images give a good idea of where there is likely to be rain by use of bright false colouring.
Looking at two images recorded a few hours apart can usually show the probable path the rain will follow. Note though that the
colours are only an indication of possible rain not that rain is actually reaching the ground.
Pager tower causing the interference bars This tower is less than a mile away and operates just 60Khz above the nearest satellite frequency - avoiding the interference is impossible difficult.
I changed the impossible to difficult following some feedback from Michael Gill G6HOM who tells me that he constructed a stripline
filter which successfully removed pager interference back in the '80s or '90s. I think I'll have to see if there is anything amongst the junk stalls
at the next amateur rally I attend which would allow me to give this a try without breaking the bank.
These images donated by Paul Glover of Worthing illustrate just what can be achieved
with fairly modest amateur equipment when there is no local pager tower intermodulation interference.
