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Hi Gerhard,
compared to the capacitive fields of the
antenna at VLF, the building will anyway be nearly a short circuit to
ground. Connecting the lightning protector will divert some of the current
which would otherwise be going through the house, but the relative
difference in the external E-field distribution will only be
small.
I have a similar situation with the LF TX antenna, which is about 10 m
above the roof of our two-floor house. There is a vapour barrier made
of thin aluminium sheets under the roof, and two of the strips can
be accessed electrically. By connecting those to ground, about 15
percent of the total antenna current could be collected, and this helped to
significantly reduce the e-fields indoors, and also slightly the loss
resistance.
On your grabber, it looks like you have switched
frequency from 8970.00 to 8969.97 sometime around 12:15 - was this a
real step, or an artifact due to receiver samplerate correction?
Best 73,
Markus
Sent: Sunday, January 23, 2011 1:53 PM
Subject: RE: LF: Transmissions on 8970Hz
Hello again!
At about 12:30UT I disconnected the lightning
protector again.
At 500mA Antenna current the wires from the roof are at
about 200V and
the current to earth was measured at 60mA.
I did this
connecting/disconnecting-test now several times but the
signal received by
Lubos in 40km distance didn't show any noticeable
difference. That's a riddle
to me.
The only difference I notice locally, is that the field-strength
in my
shack (directly under the roof) is much higher when the protector
is
disconnected because the shielding effect of all the metal parts on
the
roof isn't given any more. This also can be seen on my
grabber.
73
Gerhard
Am
Sonntag, den 23.01.2011, 13:01 +0100 schrieb Gerhard Hickl:
> Hello Lubos
and group!
>
> Yes, I started at about 11UT.
>
>
Yesterday at 12:45UT I reconnected the lightning protector of the house
>
to ground but I couldn't see any difference on the plot you sent.
>
> So I guess if connected or not doesn't play a big role. On the
other
> hand, there's a high voltage on the wire coming down the roof
which must
> lead to some current flowing to ground.
>
>
Maybe I will disconnect again in the afternoon and measure Voltage and
>
Current.
>
> Today we have strong wind here and I will see how long
I can keep the TX
> running.
>
> 73, tnx
>
OE3GHB
> Gerhard
>
>
>
>
> Am Sonntag,
den 23.01.2011, 12:40 +0100 schrieb Lubos OK2BVG:
> > Hello Gerhard,
VLF!
> > I noticed, that you had started transmissin at 11:00UT ( S/N =
15dB).
> > I saw Ossi´s transmission from 09:30 to 11:00UT, but
very weakly, as
> > usual
> >
> >
> >
Lubos, oK2BVG
> >
> >
> >
***************************
> >
> > > From: [email protected]
> > >
To: [email protected]
>
> > Date: Sun, 23 Jan 2011 10:07:28 +0100
> > > Subject: Re:
LF: Transmissions on 8970Hz
> > >
> > > Hello Daniele,
group!
> > >
> > > I will fire up later slightly below
8970.
> > >
> > > Ossi is already transmitting.
>
> >
> > > 73
> > > OE3GHB
> > >
Gerhard
> > >
> > >
> > >
> >
> Am Sonntag, den 23.01.2011, 00:54 -0800 schrieb Daniele Tincani:
>
> > > Hello VLF,
> > > > any transmission tests planned
today?
> > > > Regards
> > > > D.
> >
> >
> > > >
> > >
> > >
>
> >
> >
>
>
>
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