On Sep 11, 8:06*am, "Myron A. Calhoun" wrote:
I recently bought an automatic tuner (I know, I know; I wasted my
money since manual tuners are so easy to build) which could supposedly
tune "8-1000" ohms resistance. *I first asked the manufacturer if
maybe they meant "impedance", and they replied
"Yes, thanks for the correction". *That lead to a followup question:

( NOTE: *My keyboard doesn't have keys for "plus or minus" or "square
root" so I'll use "#" and "SQRT()", respectively.)

"Does '8-1000 ohms impedance' *include ALL COMBINATIONS of #X#jY SUCH
THAT SQRT (Xsquare + Ysquare) is in the range of 8 to 1000 (such as
#8+j0 to #1000+j0 and 0#j8 to 0#j1000), or are there some "holes" in
coverage?"

Their response was:

" We use the polar coordinate system and it covers all phase angles at
14 MHz. Obviously, plotted on a smith chart you would see the range
decrease as you depart from 14 MHz."

I haven't used a Smith Chart since I was first introduced to them in
college (1963!-() Could someone please translate their response to
simple English that I can understand. *In particular, what range of
impedances might their tuner cover on 80 meters? *40 meters? *15
meters? *10 meters?

Hi Myron,

Their response _suggests_ to me that the tuner can match loads inside
the circle on the Smith chart that's centered on the real axis and
passes through R=8 and R=1000, when used at 14MHz. I guess that's
equivalent to loads representing up to about 11:1 SWR in an 89 ohm
line. They didn't exactly say that, but it seems a reasonable guess.
It does seem like they denied that there would be holes in the
coverage.

Other than not being able to match as wide a range on other
frequencies, their response really doesn't tell me anything about the
capabilities away from 14MHz. You might be able to nail them down a
bit better if you can get them to tell you what range they can match
at 3.5MHz and at 30MHz, or other frequency you particularly care
about.

Cheers,
Tom