Chris;

Add or remove about 6 ft of the open wire line.  See if this helps the 17M issue.


I personally don't like the idea of using a 4:1 balun and much prefer a 1:1 current balun.  With the 4:1, without measuring the Z on the coax side, it may be the Z presented to the tuner is very low and thus outside the range of the tuner.   Additionally, it is most likely with almost every ATU, the greatest loss occurs when the Z is low to very low.  Hence my reason for using a 1:1 and not a 4:1.

73

Bob, K4TAX


On 2/13/2018 7:55 AM, Chris Hallinan wrote:
I have a very similar setup.  K3 -> KPA500 -> MFJ 994BRT 600W autotuner
mounted remote -> Balun Designs 4:1 -> 600 Ohm open wire line to 80 m
doublet.

It works fantastic on 80-20, but will not tune better than about 2:1 on
17.  I cannot use the KPA500 on 17 because the SWR is too high.  Nothing
I've tried works.  I'm wondering if it is simply the tuning
range/resolution of the MFJ-994BRT?  I like the idea of remote mounting, as
I have only a couple feet of coax between the tuner and the balun, thus
minimizing SWR-related feedline loss.

Any suggestions for how to get it to tune on 17?

73
Chris - K1AY
Punta Gorda, FL


On Mon, Feb 12, 2018 at 12:16 PM, John W2XS <jm...@optonline.net> wrote:

I replaced my Johnson Matchbox with a Balun Designs tuner balun. The
biggest
benefit is that the K3 ATU remembers the settings from band to band so the
QSY is very rapid. I love watching the DX spots come rolling through on my
N3FJP logging program and clicking on them to QSY to that frequency and not
have to tune up again. I use it on 80 through 6 meters with an 80m doublet
fed with KW ladder line (300 ohm).

My recommendation is to keep the piece of coax from the balun to the rig as
short as possible.  This is to minimize loss since that line will most
likely be highly mis-matched on most bands. There was a QST article not
that
long ago which detailed the losses in that situation and I was surprised at
how high they were.

I once had an MFJ balanced RF Ammeter and made measurements of the JMB vs.
the balun and they compared favorably.  DJ0IP (referenced earlier) has
kindly put those measurements on his website. (This is in the FWIW
category!)

I have not tried to substitute the tuner balun with another type but that
might be a future experiment.

73, John W2XS



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