My Tuner Problems

[Paul Gates, KD3JF]

A word of thanks to everyone who offered suggestions for how to load the antenna for 17 meters and have the tuner happy! I really did not change anything. Could it be that the problem was with the operator? How could I think such a thought!! Anyway right now the tuner is acting very nice for 160-10. We will see it that continues. It could be an intermittant problem with the tuner or coax. But, let's hope not!!
 
Paul, KD3JF
Glen Burnie, MD
FM19qd (Map Grid Square)
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[Ron D'Eau Claire-2]

Paul wrote:

It could be an intermittant problem with the tuner or coax. But, let's hope
not!!

--------------------------------

A good thing to do is to hook the tuner up to your dummy load and note the
control settings. If things go sour again, put the dummy load back on and
see if you get a match at the same settings. If you do and the antenna still
won't load, you'll know the problem is in the antenna.

Keep in mind that if you're using the internal balun in the tuner, it'll be
out of the circuit when you hook up the dummy load! You could substitute a
light bulb across the balanced feeder output for a "dummy load". It doesn't
matter what you use as long as you can tune it up for a low SWR and note the
readings. Then you'd have a reference to check back with if it happens
again. If you use a light bulb, be sure to use the SAME bulb if you need to
check things later.

Also, I didn't think of it before but since you're using the internal balun,
it could be heating on some bands. If the balun core gets hot enough and
reaches a critical temperature (called the "Curie" temperature), its
magnetic properties change dramatically. That would cause the SWR to jump
sky-high all at once. This is not a "gradual" event. Although the core takes
time to heat up, the properties of the core won't change significantly until
the Curie temperature is reached, then it will suddenly change. After it's
been allowed to cool down, the balun core will act normally again (unless it
got so hot it fractured). The heating of the balun core would be a function
of the current flowing through the windings, so it might act up only on one
band and not others, or at a lower power on one band and only at much higher
power on other bands, if at all.

Ron AC7AC

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