[Antennas] Twin lead 450 Ohm

[E. Jerold Forwood]

Hey Guys,
Am I missing something?  The last time I saw PVC pipe it was nonmetallic.
 Shouldn't it cause the same changes to ladder line as anything else that
is nonmetallic, even air?  The point of using the pipe is to protect the
ladder line from the earth/moisture it is buried in.  Use pipe large
enough to hold the line without chancing the dimensions of the line. 
Seal the pipe to prevent moisture/critters from entering, and have fun.  
        This is amateur radio.  It isn't rocket science!  You guys get
too raped up in the theories.  The guy you are talking to on the other
end won't know the difference!  I have been talking on ham radios since
the early 60's and the most fun was using old Johnson Matchboxes to load
up anything from bedsprings to wet noodles and we still talked to the
world.
73's de Jerry, K�EJF

On Wed, 11 Dec 2002 09:00:31 -0600 Sandy and Kees Talen
<windy10605@juno.com> writes:
> Great discussion on ladder line. I use the stuff exclusively (it's 
> still
> tied 
> directly to my beam) and I'm always looking for ways to improve it 
>   ........like how best to keep moisture off or bury it using PVC. 
> 
> I've always looked at feeding an antenna as having two basic 
> problems.
> One is impedance matching and the other is any balanced to 
> unbalanced 
> conversion. Beam antennas and the like are balanced loads and ladder 
> 
> line is balanced so no problem there. Since good ladder line is 
> extremely
> low loss you don't have to worry about the impedance mismatch 
> except
> at the transmitter end and you solve that with a good tuner. Two 
> parallel
> 
> "balanced" conductors do not radiate as long as the parallel paths 
> are
> not 
> altered by running next to metal, etc. Coax, on the other hand, has 
> loss
> and will require impedance matching and some sort of balun, coil 
> choke
> (that's what that coil of coax the manufacturers tell you to add at 
> the
> feed
> point is), or ferrite bead choke for the transition between the
> unbalanced 
> shielded coax and the balanced antenna. If you don't do this, the 
> outside
> 
> shield of the coax will tend to radiate. You want the signal on the
> inside
> of the coax.  
> 
> 73  Kees K5BCQ
> - - - 
> 
> Your moderator for this list is:
> Larry Wilson KE1HZ antennas-owner@mailman.qth.net
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E. Jerold (Jerry) Forwood