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Re: LF: Transmissions on 8970Hz

To: <[email protected]>
Subject: Re: LF: Transmissions on 8970Hz
From: "mal hamilton" <[email protected]>
Date: Sun, 23 Jan 2011 13:41:54 -0000
References: <[email protected]> ,<6F6098420211436FABB78BE04E5F8FAD@JimPC> ,<000901cb6215$2db60550$0401a8c0@xphd97xgq27nyf> ,<[email protected]> <B4EA2F5BDC754BC0AD7DFE6ABD01E8A2@Black> ,<25B77CFFDA13430086BE150894C4D3C3@Black> ,<5C71BB4133A642F7A2D06B26B567880D@Black> ,<B3AD784C916249F4868766DF79832B71@Black> ,<65DFBC8F38CD4AF48A62C61B6BC4DCC4@Black> ,<D99F306913F545BA9A80F5AFA1D36175@JimPC> ,<[email protected]> ,<[email protected]> ,<[email protected]> ,<[email protected]> ,<[email protected]> ,<1295773648.1527.1.camel@gerhard-desktop> <[email protected]> <1295784098.1527.29.camel@gerhard-desktop> <1295787191.1527.38.camel@gerhard-desktop> <DB8A9BF8C3494505A4623F4960F8B7F9@White>
Reply-to: [email protected]
Sender: [email protected]
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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