[Antennas] Log Periodic

[A10382]

This seems like one of the best reasons not to 'ground' (as in earth ground)
the 'return' coax shield or the non-driven side of the dipole at the
antenna.   There's a significant amount of conducting material between the
shack ground and the antenna feed points.

I believe this has the potential of creating a classic ground loop where
there would be current flowing over the shield due to different potentials
at the ground points.  Even a very small difference in ground potentials,
when connected through a low resistance path, will create a lot of
current...

I've only actually seen twice.. once in cabling computing devices between
buildings (computer in one building and the data collection device across
the parking lot).  The shield on the data cable was carrying almost three
amps at about a half a volt.

A second, back when I was still an un-ionized atom, and more severe
experience was the potential between the ships keel and a shop 40 feet
higher was almost 2 volts and the coax shield was carrying about 4 amps... a
very 'shocking' experience for the gear.

73
Frank

 ._._.
----- Original Message -----
From: "Cletus W Whitaker" <whitaker@pa.net>
To: <antennas@mailman.qth.net>; <mpb1@attbi.com>
Sent: Friday, May 24, 2002 5:24 AM
Subject: Re:[Antennas] Log Periodic


> de  WB2CPN  South Central Pennsylvania    2002.05.24
>
> As you say, the two parts of the boom are insulated from the mast, so they
> are "ungrounded", and the coax shield connects to one of the boom
sections,
> so the coax is not "grounded", or at least not there.  BUT, the bead balun
> is between the boom and the coax that goes down to your shack.  Among
other
> things, the bead balun is the demarcation between what can be "grounded"
> and what can not be "grounded".  You may "ground" the coax cable, (there
are
> a few reasons why I don't recommend this), anywhere between your shack and
> the bead balun. Just don't do it BETWEEN the bead balun and the antenna
boom.
> Sometimes bead baluns can be avoided by running the coax up through the
> inside of one of the booms and connecting it at the far end.  When I say
> "ground", above, I mean a large piece of metal nearby.  Such as the mast.
> I don't mean the stuff they grow flowers in, that's what you "ground" the
> things in your shack to.         73  Clete
> - - -
>
> Your moderator for this list is:
> Larry Wilson KE1HZ antennas-owner@mailman.qth.net
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