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Markus
The metal vapour barrier might cause
Condensation in the roof, like a tin roof on a house or shed
Do you get drips from the metal
de mal/g3kev
----- Original Message -----
Sent: Sunday, January 23, 2011 1:21
PM
Subject: Re: LF: Transmissions on
8970Hz
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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