it's the same antenna that I use for LF. The
mast is a fishing rod on an aluminium telescopic pole, pushed out of an unused
chimney. It carries three topload legs (N, W and S), about 42 m wire in
total (230 pF). The apex is 20 m AGL or 11 m above the roof, but the
effective height is only 9 m (calibrated at 138 kHz). On VLF frequencies
this is probably even a bit lower due to increased shunting effect from trees.
Assuming heff = 0.8 m, radiation resistance on 8.3 kHz would be 0.08
milliohm. With 60 Watts input, I got 0.3 A and 25 kV rms,
and radiated power (EMRP) would be around 7 microwatts.
Here's a sketch of the wire layout and the
auxiliary H- and E-field receive antennas:
One could actually see the antenna in Google
Map's slant view, but the imagery may have changed since:
Sent: Saturday, January 11, 2014 5:37
Subject: RE: VLF:
What are you using for antenna
Nice signal here,
Took the carrier off air at 12:48. Looks
like a good trace at OK2BVG, and a dash with marginal SNR in Todmorden UK.
Sent: Saturday, January 11,
2014 11:33 AM
At 10:23 I have started to transmit a
straight carrier on 8270.000 Hz, estimated ERP around 14 uW. If all stays well,
I'll leave it on for a couple of hours, trying to leave a dash on Lubos'
and perhaps Paul's spectrograms.