Hi Paul and thanks very much for the data.
Unfortunately, after the experiment, the aerial current had decreased
to zero. It seems a short developed in the tuning coil. A better design
is being considered... 2km of 0.4mm wire is on my Christmas list!
Thank-you Dimitrios for the update on your VLF work and the article.
The rapid decrease in signal with r for r<lambda/2pi is very evident
here. I had hoped to use Spectrum Lab to extend the detection
range until the coil could take no more QRO abuse!
There were some errors in my VLF report: The coil was 0.47H not 0.35H
and the XFMR was 1:5 not 5:1 (turns). This is 1:25 wrt impedance.
It was wound with 0.4 mm wire on a torroid ferrite (1.5x5x8cm) with about
4 mH for each of the 6 windings. The secondary has 5 windings in
series.
Markus, the frequency word needs to be revised. It has a rounding
error. I think it's time to rebuild the exciter with a Raspi that
can handle 32 bit floating math. Thanks for the reminder.
A 3 hour carrier on 137.777 kHz is QRV starting 0900 22 Dec UTC.
73
Joe VO1NA
PS Don't forget SAQ on Christmas Eve.
On Sun, 20 Dec 2015, Paul Nicholson wrote:
About 30 watts were fed to a 5:1 XFMR and a ~0.35H
tuning coil to the 100m wire at 10m height.
The ERP was about 3uW.
How about a long carrier, GPS or rubidium? It's a long
shot but it's a low loss path and the time of year is
good for several hours of coherent integration.
I can easily see 10uW from 1000km in one hour over
a path with a lot of land. West to east over water
will be lower loss and four or six hours integration
will make up for the lower ERP.
--
Paul Nicholson
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