Date: Mon, 28 Apr 2003 06:35:02 -0400
From: "Jay Rusgrove" <advancedreceiver@snet.net>
To: rsgb_lf_group@blacksheep.org
Message-ID: <3EAD03D6.36541070@snet.net>
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References: <2D280BB697C7EE4C979C5C89925418EFB05C1F@TNS-FBU-2E-003.corp.telenor.no>
Subject: Re: LF: RE: RE: Re: RX-LOOP
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Jan-Martin

Have you found that it makes any difference where the core is placed along the transmission line?

Jay Rusgrove, W1VD

jan-martin.noding@telenor.com wrote:

> Right,
>
> but you may also use a balun. See RSGB book about EMC (or TVI ...suppose mine is quite old..) and wind the coax cable 10 or more turns through a ferrite core with sufficiently high permeability.
>
> I use it for my active antenna, and it is of course mounted some distance above the roof. Since you don't need RG8/U type cable for LF it shouldn't be a problem to manage 10-20 turns through the toroid (provided you haven't installed the BNC connectors in the ends)
>
> 73, Jan-Martin, LA8AK
>
> http://home.online.no/~la8ak/
>
> -----Original Message-----
> From: Ashlock,William [mailto:William.Ashlock@bocedwards.com]
>
> Alan, all:
>
> >I suspect that you need to isolate the loop feed with a small transformer.
> It is possible that
> >the feed from the loop is acting as a wire aerial and is conducting TV RFI
> and noises from the
> >house *back to the loop*.
>
> Surprising how few understand the concept of the RFI actually going from the
> receiver back to the antenna site. This applies to E-probe antennas as well.
> The typical house/apartment is a mad jumble of LF RFI having both E and H
> field components. The proper RF return for remote LF antennas is the ground
> immediately under the antenna - not the safety (green wire) ground in the
> shack that connects to the chassis of the receiver. The isolation
> transformer installed in the coax lead-in offers the only way to sever these
> totally different grounds. In severe cases one is needed both at the
> receiver and at the antenna since a floating coax shield can pick up noise
> before it leaves the vicinity of the shack.
>
> BTW, an isolation transformed can be as simple as two 15-turn windings of
> #22 to #28 wire on a common 3/4"dia X 1" ferrite RFI bead found on computer
> power cords, monitor cables, communications cables, etc.
>
> Bill A
>
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