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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