On Sep 1, 11:43*am, John Smith wrote:
Uhhh, sorry to pose this question to you here but, doesn't a "tuner"
really just "shorten" and "lengthen" the feed line? *I mean, not
physically, of course. *But, it would seem to me that, this is exactly
what my xmitter and ant are "seeing."

If all the tuner did was shorten and lengthen the feedline, there
would be only one purely resistive low resistance available on the SWR
circle on the Smith Chart and it wouldn't be exactly 50 ohms. So a
tuner does one other thing - it transforms the non-50 ohm resistive
impedance to a 50 ohm resistive impedance. It is not only the
equivalent of shortening and lengthening the transmission line but
also performs an N:1 transformer function. Of course, it does that
seamlessly, i.e. it is not actually a two-step process.

When I vary the length of my ladder-line to obtain system resonance, I
have to be satisfied with purely resistive impedances between 35 ohms
and 85 ohms. I cannot achieve a perfect 50 ohms on all HF bands with
my matching method. That would require the addition of an actual N:1
transformer which is certainly possible but probably not worth the
effort. Since 35-85 ohms is perfectly acceptable to my SC-500 amp, I
don't need a high-power tuner. And since the SC-500 is spec'ed to
handle an SWR of 6:1, I doubt that an 35-85 ohm load makes it
"unhappy". If my SC-500 has ever been "unhappy", I failed to observe
that "unhappiness" but maybe I am just oblivious to such?
--
73, Cecil, w5dxp.com