Hi Stefan,
congrats for that ufb earth antenna experience! You have certainly seen
it already: from 9 to 10 UTC there was a clear trace from the east at
Paul´s grabber:
http://78.46.38.217/fbins3.html#p=1532782800&b=110&s=sp&m=cardioid&w=r&h=62&z1=0.34&z2=0.64&c=1
- it should have been your signal! But sorry: at a first glance no
signal at the DL0AO grabber but we have a lot of heavy QRN here today.
73 es gl,
Tom, DK1IS
Am 28.07.2018 um 11:43 schrieb DK7FC:
Hi VLF,
I'm sitting in my car while writing this email. I'm in JN39WI96GX and
i transmit on 8270.000 Hz with a GPS locked signal generator into an
about 450 m long earth antenna using two guide rails as the earth
electrodes on both ends. On each end there are 16 (18) massive T-T
poles holding the guide rail, providing a super good earth coupling. I
measured that they are connected to each other.
The transmitter is on the air since 9:08 UTC running 550 mA with just
75 W DC inout power into my hand warm lossy linear mode VLF PA!
I'm amazed about the low losses! At DC i got 447 mA at 50.9 V. The
wire is 0.4 mm diameter so it has 63 Ohm. That means the ground loss
is just 50 Ohm !!!! Amazing! And i have no efforts to build up a
ground connection here, i just need to connect the wire. Since the
wire losses are higher than the ground losses, i can get maybe 2 dB
more signal when buying some better wire. I already found a source
that offers 0.75 mm^2 100 m loudspeaker cable (i.e. 200m wire)for just
13 EUR....
BTW i even have an ugly old scope here which is battery powered. I can
see that the phase of voltage and current is slightly inductive, maybe
30 deg or so. So i could series resonate the antenna with some C. This
is for the next experiment...
The signal becomes visible on my grabber now, in 424 uHz and also some
bright pixels in the 3.8 mHz window.
I'm going to stop the carrier at 10:08 UTC, after 1 hour. Then i'll
continue on 5.17 kHz!
BTW the antenna , if it works like a real loop, is beaming directly to
Paul Nicholson ;-)
73, Stefan
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