Hi Joe,
Just as an inspiration for a VLF coil design, here's an image of the
first coil of a stackable set of coils for VLF:
http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/coil1.jpg
I just finished to wind it. It has 172 mH. A 2nd and a 3rd and
a 4th and and and.. will be wound later. The advantage of that system
is that i can tune to any frequency, without steps. Also it is much
easier to repair than my large VLF coil for 2.97 kHz.
It uses 0.25 mm diameter wire and is intended to be driven at 300 mA
antenna current. The system will focus on frequencies < = 5.17 kHz.
It took about 7 hours for the winding and 2 hours for preparing a
construction to rotate it by a motor.
With that single coil i could resonate to 17.5 kHz. But with a second
one i will already be quite close to 8.27 kHz. With 4 of them i will
already reach 5.17 kHz. And 6 of them could be fine for 2.97 kHz! Maybe
i will build 8 of them to reach 2.17 kHz :-)
The DC resistance of the single coil is 267 Ohm, so the losses will be
25 W per coil. Ah and the coil diameter is 0.3 m (average).
The wire is hold in place by Kapton tape which is cheaply available
from Amazon.
73, Stefan
Am 07.09.2017 14:10, schrieb [email protected]:
This is amazing, Paul. To copy < 0.00001 watts across
the pond with the carrier drifting about is an amazing feat.
The daytime signal is used because more atmospheric
noise is propagated at night?
Unfortunately there is now a delay in getting the gps board but
better stability is certainly in the future.
Thank-you for your efforts and monitoring.
73
Joe VO1NA
On Thu, 7 Sep 2017, Paul Nicholson wrote:
Joe VO1NA wrote:
Today the aerial was disconnected at 0950
utc
Here's a non-coherent average over 8 days of 10:00 to 20:00
http://abelian.org/vlf/tmp/170907a.gif
Impossible to do coherent sum with this many days, without
GPS frequency lock.
Not bad for 8uW ERP but it should do a lot better with a precise
frequency.
--
Paul Nicholson
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