Clemens, LF group!
This is exactly the opposite that I experienced with the Mini-Whip.
The higher I brought it up (= the farther I brought it away from the
noise source, commonly called "house"), the better the SNR.
Today I connected the shield of the cable to the lightning protection
system up on the roof and couldn't find any difference so far.
I'm using a 5m fibre-glass pole fixed to the chimney as a support for
the probe and the shield of the feeder is only grounded in the shack.
73
OE3GHB
Gerhard
Am Donnerstag, den 11.08.2011, 13:32 +0200 schrieb Clemens Paul:
> Hi Stefan,
>
> > The pole that is on a noisy roof (and its noisy ground) and on the other
> > side
> > the pole that is far away in the garden, with its own and clean local
> > earth.
> > In the garden a metallic pole should make no difference, as you say.
>
> How true.
> My miniwhip was completely unusable on the top of my roof,
> with or without connecting the coax shield to the lightning
> gr.. ehm reference plane.
> So I decided to put it in the middle of thegarden where it is only 30cm
> above the lawn.
> Here connecting the coax braid to a 3m long earth rod was essential
> to get rid of the noise.
> Now this setup is good enough for receiving SAQ with up to 30dB S/N.
>
> 73
> Clemens
> DL4RAJ
>
>
>
>
>
> ----- Original Message -----
> From: "Stefan Schäfer" <[email protected]>
> To: <[email protected]>
> Sent: Thursday, August 11, 2011 9:58 AM
> Subject: Re: LF: Re: HB9ASB...
>
>
> > Hi Gerhard,
> >
> > I think one has to compare two different situations:
> >
> > The pole that is on a noisy roof (and its noisy ground) and on the other
> > side
> > the pole that is far away in the garden, with its own and clean local
> > earth.
> > In the garden a metallic pole should make no difference, as you say.
> >
> > 73, Stefan
> >
> >
> > Am 11.08.2011 05:33, schrieb Gerhard Hickl:
> >> Roelof!
> >>
> >> With interest I was following all the discussions about the "Mini
> >> Whip"-like antennas.
> >>
> >> In your description of the "PA0RDT Mini Whip" you suggest to use a non
> >> metallic pole for mounting the probe and an (optional) earth-rod to
> >> ground (sorry Andy!!) the shield.
> >>
> >> I might be completely wrong but isn't it the same when one uses a
> >> grounded metallic pole and connect the shield of the coax on top of this
> >> pole?
> >>
> >> BTW: I have an insulating pole (5m) on top of the roof and yet no
> >> grounded shielding of the coax but just in the shack. I will connect the
> >> shield to the lightning protection system at the bottom of the pole and
> >> see about the difference.
> >>
> >> Actually it isn't even a true coax cable but a singe shielded twisted
> >> pair where the two inner wires are in parallel....Z=? Who knows????
> >>
> >> So considering my "fluffy" set-up, I think my VLF grabber is performing
> >> very well but for sure there is room for improvements as well.
> >>
> >>
> >>
> >> 73
> >> OE3GHB
> >> Gerhard
> >>
> >>
> >>
> >>
> >>
> >>
> >> Am Mittwoch, den 10.08.2011, 21:26 +0200 schrieb Roelof Bakker:
> >>
> >>> Hello Minto, Stefan,
> >>>
> >>> Some food for thoughts:
> >>>
> >>> When I tested a mini-whip in the garden with battery feed and also with a
> >>> battery fed SLM, I found the noise lower than when used inside and
> >>> operated from the mains.
> >>>
> >>> The coax cable from the house station was connected in parallel with the
> >>> mini-whip by means of a BNC T-piece.
> >>> The noise increased by 9 dB. My assumption is that this noise is received
> >>> on the shield of the coax inside the house.
> >>>
> >>> Without connecting the shield to a separate radio earth, the noise
> >>> received on the shield inside the house will travel over the shield all
> >>> the way to the antenna. There the noise will be received by the sensitive
> >>> probe. This will be by means of capacitively coupling, I guess. Many
> >>> people have reported a large drop in local noise by connecting the shield
> >>> at the bottom of the mast.
> >>> This also applies to normal active whips of course.
> >>>
> >>> 73,
> >>> Roelof, pa0rdt
> >>>
> >>>
> >>
> >>
> >
> >
> >
> > -----
> > eMail ist virenfrei.
> > Von AVG überprüft - www.avg.de
> > Version: 10.0.1392 / Virendatenbank: 1520/3826 - Ausgabedatum: 10.08.2011
>
>
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