[Elecraft] OT: Now Balun effectiveness

Wed Mar 24 20:07:01 2004

The only thing I can add [if mobile] where the tuner is by the radio and
antenna is on trunk you are tuning a combination of the antenna and coax.
Now I have read the tuner should be [since it is tuning antenna] as close as
possible.  However, for the purists I am not sure if the differences are
really that much.  It just made sense in my case to put tuner as close to
antenna as possible.  It seemed to make the tuner more stable while matching
the antenna during operation.

Chuck

-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Darrell Bellerive
Sent: Wednesday, March 24, 2004 6:17 PM
To: Don Wilhelm
Cc: Elecraft Email List
Subject: Re: [Elecraft] OT: Now Balun effectiveness

Thanks for the great replies! See below for my comments.

On Tue, 2004-03-23 at 21:44, Don Wilhelm wrote:
> One just must 'hit the books' - 
I have read ARRL's handbooks and antenna books, Maxwell's Reflections,
and Sevick's Building and Using Baluns and Ununs, as well as Roy
Lewallens' notes. There seems to be a bit of uncertainty with respect to
baluns in multiband antenna systems. One advocates putting the balun
between the transmitter and the tuner, the other states it make no
difference. One states that the balun will transform impedances, another
that impedance transformation is only valid over a small range of
frequencies. It looks like more empirical research is still required.

> >Put the remote tuner at the antenna feedpoint or feed with low-loss
parallel
> line from the remote tuner to the antenna and the losses will likely be
> small.  Bottom line - keep the SWR on the coax low and the losses will
> likely also be low - high SWR lines need to be open wire or ladderline
> balanced lines.  Keep in mind that it is not practical to go to extremes -
> an SWR of 2:1 on most coax is quite tolerable when considering loss at HF
> (VHF and UHF are quite different considerations - the loss becomes greater
> as the frequency increases).
> ---------------------------------
Every time I bring up the topic of remote controlled balanced tuners, I
get met with blank stares, or told to "just use a balun". I kept
thinking that I was missing something. Perhaps some new balun design or
particular combination of multiband antenna, and feedline dimensions;
Perhaps that someone had figured out a configuration using a balun and
coax feedline that had losses comparable to open wire feeders.

So all in all, I still believe that a multiband doublet antenna fed by a
tuner either via open wire or ladderline or directly will exhibit lower
losses than coax feed with a balun. While Lewallen's work on the
symmetry of the current balun being the same regardless of which side of
the tuner it is on, there is at least theoretically less loss with it on
the transmitter side. Whether that justifies the added complexity of the
balanced L network is doubtful.

So I am still an advocate of the remote tuner in situations where
routing open wire or ladder line feedlines is not convenient. I would
now however accept an unbalanced L network design followed directly by a
current balun whereas before this discussion I would not have accepted
the balun after the tuner or an unbalanced tuner design.

So Wayne and Eric, back to my original question: Any plans for a remote
controlled antenna tuner?

Darrell VE7CLA K2 #1973

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