Tuner/Balun Question

[Parker Buckley]

I just read the Aerials article by Krusty Kurt in the October issue of World
Radio.  Near the end of the article, Kurt is describing a well known method
of running parallel coax through the wall to connect ladder line to the
antenna tuner.  His method ties the shields together at both ends to get 100
ohm feedline, while I've always left the braids near the ladder line
floating.  What really caught my attention, however, is his comment that you
can run the parallel coax lines straight to the tuner without a balun.  I've
always used a balun in this setup; either 4:1 or 1:1.  I recall emails to
this reflector in the past describing connection of ladder line straight to
an Elecraft tuner with no problems.  I'm now wondering if I could ditch the
baluns in my installation.  Any thoughts/experience with this?  Is the
output from a tuner balanced at the coax connector up until such time that
it's connected to an unbalanced load like a single coaxial line?

 

Parker

WD8JOL K2 #2636

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[Don Ehrlich-2]

The output of a conventional tuner is not balanced and is intended to be
connected to an unbalanced load like coax.  However, it certainly is
possible to connect it to a balanced feedline and it *may* find a match when
so connected.  However, the "balanced" feedline will not be balanced when
that is done because one side is connected to ground.  The result is that
power may be delivered to the antenna but the feedline will be radiating and
the pattern from the antenna is unknown.

That's the short answer ... I await the many antenna experts on the list to
embellish it.

Don  K7FJ

>I just read the Aerials article by Krusty Kurt in the October issue of
>World
> Radio.  Near the end of the article, Kurt is describing a well known
> method
> of running parallel coax through the wall to connect ladder line to the
> antenna tuner.  His method ties the shields together at both ends to get
> 100
> ohm feedline, while I've always left the braids near the ladder line
> floating.  What really caught my attention, however, is his comment that
> you
> can run the parallel coax lines straight to the tuner without a balun.
> I've
> always used a balun in this setup; either 4:1 or 1:1.  I recall emails to
> this reflector in the past describing connection of ladder line straight
> to
> an Elecraft tuner with no problems.  I'm now wondering if I could ditch
> the
> baluns in my installation.  Any thoughts/experience with this?  Is the
> output from a tuner balanced at the coax connector up until such time that
> it's connected to an unbalanced load like a single coaxial line?

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[Parker Buckley]

Don,

Okay, that's as I suspected.  It makes sense to me that the tuner could
resonate the antenna-feedline system, but that the currents may remain
unbalanced.  One of my antennas is a quad fed with open line, and such
operation would probably skew the directivity.  I think I'll stick with my
baluns....

Thanks,
Parker


Snip

The result is that
power may be delivered to the antenna but the feedline will be radiating and

the pattern from the antenna is unknown.

That's the short answer ... I await the many antenna experts on the list to
embellish it.

Don  K7FJ


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