content-class: urn:content-classes:message
Date: Mon, 28 Apr 2003 13:56:48 +0200
Message-ID: <2D280BB697C7EE4C979C5C89925418EF1BF5D3@TNS-FBU-2E-003.corp.telenor.no>
Thread-Topic: LF: RE: RE: Re: RX-LOOP
Thread-Index: AcMNcq07Mbg/XobmQZawNJ9RlXhO3wAAFhvw
From: jan-martin.noding@telenor.com
To: rsgb_lf_group@blacksheep.org
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Subject: RE: LF: RE: RE: Re: RX-LOOP
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Not really,
I forgot about it when I mounted the frame antenna, so it may not be much problems at my QTH in suburban area, but I experienced some noise problems when the active antenna was mounted just above the roof. Mounted it further up above the roof and added a ferrite choke type balun - hidden just under the side of the roof. And didn't find it to be much noise problems any more. It is aluminium type roof plates.
So it is very difficult to say whether it has improved or how much effect it really has. As long as I haven't experienced any particular noise it is all based on guesswork and impossible to figure out what and where the improvement could be done.

I am familiar with EMC - or say - balance problems - from situations at work, when solving problems with noise tansients on 2MB PCM systems on long telephone lines.

73, Jan-Martin
---
J M Nøding, Datakvalitet, TTS, Kristiansand
http://home.online.no/~la8ak/
Telefon 0047-380-52660, 9077-7126 (QTH: 0047-380-87178)


-----Original Message-----
From: Jay Rusgrove [mailto:advancedreceiver@snet.net]
Sent: 28. april 2003 12:35
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: RE: RE: Re: RX-LOOP


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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