Satgen 373  FFTDSP Experiments   by GM4IHJ                18 May 96

Amateur Radio Moonbounce experiments have spawned several interesting
ideas. Prominent amongst these is the use of computer software which
employs the mathematical technique of Fast Fourier Transforms. Program
FFTDSP42 from AF9Y will, when loaded into a 386+math processor/486/or
Pentium computer fitted with a sound card, produce a screen display of
the continuous output of 640 2Hz filters sampled every half second.
Thereby allowing the eye to see weak signals which are inaudible in
noise. The screen can be saved as a GIF file.

Please be aware that DSP Digital signal processing is a term now in
wide use for a variety of quite different hardware and software. Here
the concern is solely with a software package which though originally
developed for Moon bounce has hundreds of different uses in amateur
radio weak signal studies.

At GM4IHJ the main concern is satellites with particular attention to
their use as downward looking propagation probes. In addition sub
horizon and antipodeal tracking of HF satellite downlinks (RS10,12,15)
has been dramatically improved by using this software. Equally
important it has been noticable how the software enhances satellite
educational presentations of features such as Doppler shift, Faraday
effect, E layer effects and, propagation and attenuation anomalies due
to scintillation and aurora. Whilst from an operational viewpoint the
software is excellent for displaying evidence of spin modulation,
tumbling , and variations in ground antenna pointing and polarisation.

Outside the field of artificial satellites, the program gives a new
edge to moonbounce studies , and it may help prepare this author for
the experiment to detect the Mars probe 70 cm beacon in late 96.
Meanwhile it can also be tried out on radio astronomy targets such as
Jupiter HF radiation, and pulsar studies.

More down to earth,the software gives interesting results studying HF,
50 Mhz and 144 Mhz terrestrial beacons. But most interesting of all
has been its use as a visual observation tool for meteor scatter.
There are at least 3 Euro TV stations about 100Hz apart in carrier
frequency around 48.2510 Mhz . Using the computer display it is
possible to note that some meteors propagate all three signals whilst
others propagate only one . At the moment 1000ut 12 May there is a
visual ping every 4 or 5 seconds. It will be interesting to see what
the August Perseids look like on this display . So must get the IHJ
copy of the software registered with author AF9Y.

Full details of the software with a downloadable demo copy are on :-
http//www.webcom.com/~af9y       the authors email is mwcook@cris.com
and his postal address is Mike Cook AF9Y  501 E Cedar Canyon Road
Huntertown Indiana 46748 USA.