Satgen 617 Satellite Survey  by GM4IHJ    (BID SGEN617)   2001-01-20

The present interval whilst we wait to find out whether AO40 is going
to be useful or not. Is perhaps, a good time to look around at what
is available to the space/satellite enthusiast , elsewhere.

When did you last try a search of the bands to see how many
satellites you could detect and perhaps identify ? These days there
are very few HF satellite downlinks. But RS12/13 and sometimes RS15 ,
can provide lots of interesting challenges.

While at VHF there are literally a hundred or more downlinks to check
and identify. The band 136 to 138 MHz has some interesting Weather
satellite APT signals from both American , Russian and Chinese birds,
plus the Orbcom satellites. Then on 143.625 the International Space
station is often on the air passing official and private traffic even
when no amateur radio ARIS operation is scheduled. At 145.8 to 146
MHz amateur satellites AO10 and RS12/13 are regular features and
slightly higher in frequency below and above 150MHz there are a
continuous series of Russian and American navigation satellite
signals .

If you have a general coverage receiver tuning 150 to 300 MHz.
In between 150 and 205 MHz there are the curious electronic
intelligence satellites which transmit simultaneously on two
harmonically related frequencies Eg 153.6 and 204.8 MHz. Then just
above them there is a large block of military satellite downlinks
between 240 and 280 MHz. These latter employ 50 kHz channel spacing
and are mostly used by mobile units such as warships.

At UHF around 400 MHz there is a second group of navigation satellite
signals. Most of which transmit unmodulated carrier to provide a more
accurate , less disturbed dopplering signal for Transit and other
navigation systems. While slightly higher in frequency there are the
low earth orbit amateur radio communications satellites of the mode J
type personified by the two Japanese representatives FO20 and FO29.
Also in this band is the single channel FM voice satellite AO27 and
SO35 the South Africa satellite. Though this latter satellite can be
difficult at best for Northern Europeans, because of its low orbital
inclination angle and limited power budget.

Alongside the above voice and CW  UHF satellites there are more than
a dozen varied packet radio satellites . Some like the UOsats and
Koreasats are regularly available, but most of the others are heard
only infrequently or not at all.

All these signals are affected by Faraday rotation , and , less
frequently, propagation disturbances such as aurora, auroral Es,
scintillation, and Sporadic E ( yes even in January when we get a
scaled down Winter season version of the much stronger summer day
SpE). If your computer supports FFTDSP software you can see these
effects at first hand. You can also build up a library of signal
spectra which allows you to check, whether you have seen a particular
signal pattern before and recognise its signal type.