In 21.01 26/04/00 , Larry VA3LK wrote:
The notion of excellent transmitter frequency stability is critical, but so
also is the necessity of having fully automated receiving systems to take
advantage of the fully automated transmitting systems!
Larry, we (Renato IK1QFK and me) use an automatic system to monitor
the VLF/ELF activity. A PC runs Spectrogram at low speed (a screen fills
in 20 minutes, as with Spectran at minimum speed), and an automatic
program takes screenshots at 18 minutes intervals. We use "2020" by
American Software. Every day or two you look at the screenshots and
evaluate the results. A QRSS signal would be easy to detect!
The system is not automatic, but permits to find opening hours. I used
this in last winter to monitor CFH; it worked fine. And all the necessary
software is available on the web.
For a detailed description, the site of Renato is at :
http://web.tiscalinet.it/vlfradio/
The receiver frequency stability is a major issue, however. But as Andy
points out, a good standard is easy to get (you already have the HP 10 MHz
oscillator inside the 5328A, a very good one).
Renato's radio (an old FT707, if I remember well) has some dozens of
different Xtals to form the final frequency ... unthinkable today. It drifts
half a kHz per hour at power-on ...
73, Marco IK1ODO
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