Message-ID: <4DF0A3C1.3050208@iup.uni-heidelberg.de>
Date: Thu, 09 Jun 2011 12:43:13 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: antenna for 137kHz.
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Hello Martin,

I assume you're talking about RX antennas?
If you want to use a loop, maybe you want to build an own loop for 137 
kHz that is placed as far as possible from the house. The size (enclosed 
area) may be smaller. You may use a coax cable going to the shack (maybe 
RG174) that is grounded in the garden, with an own LF earth rod. Then 
you can use a transformer to couple the signal to your RX.
There are several ways to do it and the best SNR that can be achieved 
depends on the local noise situation.
I am rather a fan of small E probe antennas since they are easy to build 
and can easily be lifted to 10 m above GND, e.g. with a small plastic 
rod. But my experience with loops is small, maybe i become a fan of them 
too soon :-)

73, Stefan/DK7FC

Am 09.06.2011 12:07, schrieb Martin Evans.:
> Gentlemen - some advice, please.
>
> My radio room is in a bedroom at the back of my house.
>
> Currently, I use a wire running from the bedroom up to a pole on the 
> chimney about 35ft (10m) above ground, then to a pole at the bottom of 
> the garden about 100ft (35m) away, then down to the bottom of the 
> pole, where it is tied off.
>
> I tried running the wire back to the house (end not connected to 
> anything)  at about 8ft above ground (2.5m) but this runs alongside a 
> long building with my office, with electicity cables, computers, etc, 
> so it picked up a lot of noise.
>
> The signals seem "cleaner" when this return run is cut off.
>
> How can I improve this setup?
>
> I am thinking of pulling the far end of the wire over to the other 
> side of the garden and running it back to the house there, probably 
> about 10ft (3m) above ground, then back inside to make a loop.
>
> I would then have a loop aerial in a 45 degree plane, roughly.
>
> Does this sound as if it could be an improvement over my current 
> setup? Would lifting the bottom of the loop up to be more horizintal 
> be better or worse?
>
> Any other suggestions?
>
> My garden runs roughly East-West. Does my current "Inverted U" aerial 
> have any directivity at this frequency (137kHz)? What would be the 
> directivity of my proposed 45 degree loop?
>
> Thanks for any help & suggestions,
>
> Martin  GW3UCJ deep in the Swansea Valley!
>
>