Hello Gerhard,
glad to read about your experiments. I'm looking forward to see your first
trace on one of our grabbers!
That's an interesting note about the sound from the antenna wire. I didn't
notice that as a separate effect when transmitting at home, but as in our
small garden no part of antenna is not far from the coil, and the residual
noise from the coil itself may have covered the antenna component.
In terms of a physical explanation, it could be an electrostatic effect of
the AC charges on the antenna in the atmospheric DC field (normally on the
order of 100 V/m). In analogy to the earth's magnetic field at the coil,
this would be a linear effect, generating 9 kHz vibration - a kind of
inverse field mill. Perhaps it could even be used as a storm indicator, as
the DC field under active clouds is much larger, and the antenna would
become louder.
Another possible mechanism could be the onset of corona, though probably not
yet at your antenna voltage.
Regarding the cats' hearing, I can definitely confirm your observation. Our
two cats didn't seem to be bothered by the transformer or coil noise at all.
They were simply inspecting the hardware with due curiosity, and one of them
even took a nap in the vicinity. And I am sure they do hear well, proven by
their unambiguous reaction to certain little noises coming from the kitchen
;-)
Best 73,
Markus (DF6NM)
From: Gerhard Hickl
Sent: Saturday, November 20, 2010 5:26 PM
To: [email protected]
Subject: VLF: Funny things!
Hello group !
Among others, I'm experimenting on VLF.
Today, I applied about 70W on my 16m high Marconi. The loading coil is a
Variometer (460-580mH) and the capacitive load of the antenna is about
600pf. The antenna current was measured at about 300mA.
1. The coil is whistling but also the wires running across my property
do. I could hear the high tone even in abt. 70m away from my place. This
could cause problems with my neighbours, I guess.
2. You know Christmas time is coming and so I set up different lights
for decoration today. One is a light-chain consisting of about 80 LED's
in a small tree, right in the middle of my garden. When it got dark, the
LED's were enlighten even without any power supply connected. So this is
the proof: The antenna is radiating!!!
3. Cats: I thought the cats won't show up as long as the TX is on,
because of the loud whistling tone but they completely ignored the noise
and didn't behave any different!! It is said that a cats ear is at least
twice sensitive compared to a human ear and I have no doubt that they
can hear very well up to higher frequencies. So I assumed this tone must
be extremely annoying to them, because it is almost to me. So either
they are deaf or dumb? Or what?
to be continued
73
OE3GHB
Gerhard
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