Hello Dick,
Your simulation confirms the measurement of DF6NM, the near field signal
drops very fast (20dB for 1km -> 2km).
Can you simulate a magnetic (loop) antenna instead of a vertical ? I wonder
if that gives any different (better) result.
I used GRNDWAV3 (btw fine piece of work) to calculate the far-field signal
strength from 5km upward. When doubling the distance step by step the
result is a 6dB decrease each time, up to 640km. From there on the
attenuation increases significantly. But who worries for that at this moment.
So the main burden could be to get the signal 5km out, for there on you
'only' need to quadruple the ERP to double the distance.
One more thing : the VLF signal strength is most likely very stable at
distances below 1000km, so what stops us from using DFCW at dotlengths of
several minutes. Achieving 0.001Hz frequency stability of the TX and RX
should be 'peanuts' (just 1ppm) what allows us to take optimal advantage of
very long dotlengths.
Any station that can get it's signal copied at 5km distance using 3 sec/dot
should have a range of about 70km at 10 min/dot.
73, Rik ON7YD
At 15:09 13/07/01 +0200, you wrote:
To All from PA0SE
Computer program Antenna Optimizer by K6STI permits to calculate the near
field of an antenna up to a distance of 2km. I did so for a vertical for
9kHz. I had to make it 180m high before computation was possible.
The field is computed for a radiated power of 1kW. But what matters is the
way the field strength changes with distance.
Sorry for the poor quality. The file cannot be saved outside the AO
program or whatever that is called in computer speak. So I had to print
them using "Print Screen" and scan the printed result.
I first included the near magnetic field as well but the Reflector
apparantly did not accept the file (50kB). When I see this message has been
accepted by the Reflector I will send the magnetic field values by a
separate e-mail.
73, Dick
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