Yesterday (July 1st) I attempted to
improve the cooling and to reduce the acoustical
emission from my VLF loading coil. A large 12 volt
fan was placed above the top of the coil, powered
directly by the rectified antenna current. The high
voltage and electric fields at the motor did not
seem affect the electronic commutation. To
reduce heat buildup inside the enclosure, the inner
wall of the lower blue bucket was lined with a coil
made of thin polyethylene tube, which was manually
fed with cooling water by swapping the upper and
lower canisters from time to time. Finally the
remaining narrow slot between the two outer buckets
was tightly sealed with tape, which indeed
attenuated the annoying coil beep very
significantly.
Then I ran a carrier on 8270.0025 from 11 to 15:30
UT. Unfortunately at that time, the QRN was already
quite strong, preventing a detection in the 424 uHz
grabber windows of DK7FC and OK2BVG. But after the
long transmission, a couple of promising brighter
pixels did show up at the right place in the 47 uHz
instances of in Heidelberg, and probably also in
Cumiana at IK1QFK.
Today's weather was not favourable but we expect
better conditions tomorrow morning. So if all goes
well, I will try to repeat the carrier transmission
on Sunday morning 6 to 11 UT
(July 3rd, overlapping with SAQ), hopefully in lower
background noise. Tomorrow's goal would be clearer
detection in Cumiana, but of course I'd also very
much appreciate possible detections from anyone
anywhere else. I will also try to send more EbNaut
later but not tomorrow.
BTW I have also reactivated my slow VLF grabber
windows on the permanent "summer antenna" (a passive
E-field probe in the garden), which is permanently
serving the 137 kHz and Loran-C Receivers. On
LF it is somewhat plagued by ADSL and powerline
pickup, but the QRM situation may be different at
8.27 kHz. I actually need some amateur signals to
find out how good it is ;-).
All the best,
Markus (DF6NM)
