Message-ID: <00c401cc5826$49523e70$71a9c00a@Clemens04>
From: "Clemens  Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <4E418609.6020500@iup.uni-heidelberg.de>	 <67A6F7BF45BF4A0193A3DCB53000A283@PcMinto>	 <008401cc56ce$2f1fb2c0$0401a8c0@xphd97xgq27nyf>	 <12C475F3F4C84B818461753F2E8A60A6@PcMinto>	 <4E41AECB.90808@iup.uni-heidelberg.de>	 <8D68749D37B94275855FDBA46A3F6C97@PcMinto>  <op.vz0iyui5yzqh0k@pc-roelof> <1313033619.1543.20.camel@gerhard-desktop> <4E438B8B.1060800@iup.uni-heidelberg.de>
Date: Thu, 11 Aug 2011 13:32:08 +0200
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Subject: Re: LF: Re: HB9ASB...
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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" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
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
>>>
>>>
>>
>>
>
>
>
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