[ARC5] Tuning up BC-230 and ARC-5

[Dennis Monticelli]

All my antennas are balanced and so are the feedlines and so is the tuner.
It's important to maintain balance throughout the system if one wishes to
keep the feedline from either radiating or picking up signal (including
noise).

The most overlooked part of this fully balanced system is the tuner.  Many
of the so-called balanced input tuners are not well balanced at all.  QST a
while back ran a collection of tuners (both modern and vintage) through
their paces with various loads and on all bands.  They also measured the
degree of balance.  The hands down winner for balance was the Johnson
Matchbox (both KW and Jr).  I use a Matchbox Jr.   The ferrite balun based
balanced input tuners did not fare well and were particularly bad on the
upper bands.   Of course you could roll your own balanced tuner and do a
good job if you pay attention to details.  Remember even if you do a great
job installing a balanced feedline should the "terminations" of the
feedline (i.e. antenna and tuner) not also be well balanced, then unequal
currents are going to flow on that feedline and it will become part of the
antenna whether you like it or not.

As an aside, many hams turn away from a tuner like the Matchbox because
they cannot get a perfect SWR on all bands.  Even after playing with
antenna length or feedline length there always seems to be one band or two
that doesn't want to play along.  So they turn to a more modern tuner that
has a wider tuning range.....that is also lossy and not well balanced. Well
there is a better solution.  You can use the unbalanced ATU in your rig to
clean up residual SWR or you could use a good quality unbalanced external
tuner in series with the Matchbox.  On the bands where the SWR is already
good via the Matchbox, just run the other tuner on bypass.  On the problem
bands as long as the SWR is "dipping" with the Matchbox, there is a
resonance going on within the Matchbox so it's doing its job acting as a
wonderful balun.  It just can't transform the impedance all the way to 50
ohms.

Dennis AE6C

On Wed, Mar 30, 2016 at 9:39 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> On 31 Mar 2016 at 17:19, AKLDGUY . wrote:
>
> > The more I deal with coax, the more I hate it.
>
> Join the club... i.e., me too.
>
> > I'm trying to get
> > back to balanced feed like the hams of the 30s used.
>
> And like I used in the '50s through '70s.
>
> > Balanced feed = less likelihood of radiation off the feedline
> > and less pickup of locally generated noise.
>
> Indeed.
>
> Best antenna I ever used was an open-wire-line fed inverted vee.
>
> My "new" antenna will be an open-wire-line fed vee-beam, "swung" 90
> degrees so it is
> vertical with the end of one leg in the top of a 110 foot tall tree, and
> the end of the other leg
> near the ground under the tree. Legs are 132 feet long.
>
> I'll be using 600 ohm "ladder-line". My balanced coupler is one I built
> back in the 1960s from
> parts taken from a Wilcox 96 transmitter.
>
> I can hardly wait. It will be the best antenna I have been able to use in
> over 30 years...
>
> Ken W7EKB
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