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:[email protected]]
Sent: 28. april 2003 12:35
To: [email protected]
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
[email protected] 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:[email protected]]
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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