[RFI] stealth RFI
W4EF at dellroy.com
Mon Jun 16 11:06:21 EDT 2003
> Let's not forget that even good, balanced radials do radiate.
> It's only in the far-field that their RF becomes negligible.
> AC wiring near radials WILL couple RF from them.
> And you can get a nasty burn off the end of a resonant radial.
Yes, that was quite clear when I only used 2 radials per
band. Everything on the 2nd floor of my house was
lightning up with RFI. That is why I expanded the radial
field. The idea was to spread the energy out over mutiple
radials and create a shield between the fields from the
antenna and the house wiring. As you correctly point out,
this doesn't occur with only 2 radials. Sixteen is probably
a bare minimum, but it does seem to have improved
things considerably as compared to 2 radials. Certainly
as radial field density was increased at some point it
will start to approach the effectiveness of a continuous
metal sheet. The idea was to come up with a reasonably
good approximation to this. In any case, when I get the
old TV fixed, I will put it back to see how much (if any) of
the TVI improvement was really due to the extra radials,
and how much (if any) was due to the differences
in the TV's.
73 de Mike, W4EF........................................
----- Original Message -----
From: "Cortland Richmond" <ka5s at earthlink.net>
To: "Ted Bohrer" <N7QY at arrl.net>; <rfi at contesting.com>; "Michael Tope"
<W4EF at dellroy.com>
Sent: Monday, June 16, 2003 9:36 AM
Subject: Re: [RFI] stealth RFI
> Michael Tope <W4EF at dellroy.com> wrote:
> > story house. The TV is upstairs which puts it right under
> > the counterpoise for my vertical. Adding a bunch of ferrite
> > beads to the coax that runs between the CATV wall outlet
> > and the TV seemed to help (I used Amidon type
> > 77 material), but it didn't get rid of the problem entirely. I
> > also added more radials on the roof in order to help create
> > a shield between the antenna and the electrical wiring in the
> > attic. I started with 2 tuned radials on each band (10, 15,
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