APT satellites give about
12 good images a day, wherever you are in the world. The
resolution is 4km per pixel and there are visible and infrared
sensors. This is a simple system where the satellite is in low
earth orbit and very easily received at 137MHz. These
simple omni-directional antennas do not need moving or tracking
to receive the satellite. The satellite is so strong that when
is about 10 degrees above the horizon perfect results will
There are two problems with
using receivers not specifically designed for weather satellites.
The first and most important is bandwidth, an APT signal needs
about 40kHz of bandwidth, between 30 and 50 is OK. Most scanners
have 15kHz which is far too narrow and 180kHz or more which
is far too wide. Only a few scanners have the correct bandwidth
and these are currently the AOR5000 and Icom IC-PCR1000. The
second problem with all scanners, including the ones mentioned,
is that a weather satellite system needs a very good performance
receiver, one that provides high sensitivity, good signal to
noise and high immunity to other adjacent transmissions. So,
you may get your scanner to work, but it will not provide the
results you see in our colour images. Our PROscan receiver
has been specially designed to provide optimum performance.
The Quadrifilar helix
antenna is designed especially for marine use. It is
made entirely from 316 stainless steel and derelin
plastic and is extremely strong.
PROscan APT receiver
This receiver has become a legend in the weather satellite
field with over 3,500 in service all over the world. In tests
this receiver has outperformed every other similar receiver.
It provides greater signal to noise and hence better image
quality. It is more resistant to pagers and other nearby radio
transmissions. It is easy to use and has direct frequency read
out. It can be computer controlled so that completely automatic
operation is possible.
6 known APT satellite frequencies are fitted and just in case
there are two spare unallocated channels. There is selectable
channel lockout if some satellites are not required. The PROscan
receiver uses a lot of filtering, 3 coils in the optional preamplifier,
4 coils in the RF amp (total 7 coils at RF), 3 coils in the
oscillator, 1 matching coil at first IF, 5 ceramic filters
at first IF, 5 coils at second IF (total 11 IF filters) and
a quadrature discriminator for linearity and high ultimate
signal to noise. As with any weather satellite receiver, you
need an interface and software to get images into your computer.
The Enhanced Polar Preamplifier
is designed to go with our Quadrafilar Helix antenna, although
it can equally be used with our crossed dipole or any other
antenna where the best possible performance is required. It
has the lowest noise figure on typically just 0.5dB and bandpass
filtering giving over 50dB rejection to pagers on 153MHz.