On Mon, 01 Aug 2005 12:21:59 GMT, chuck wrote:

If he has an RF bridge, couldn't he simply terminate the tuner's input
with 50 ohms resistive and measure the impedance at the tuner's output?
Well, the conjugate, anyway. I'm trying to imagine the benefit of doing
it that way, rather than simply measuring the impedance at the
transmission line directly.

Chuck,
NT3G

I will break my own rule of not responding to responders and answer
your question - otherwise you would assume that I was ignoring you.

If I might answer a question with a question - why do you think that a
tuner would give up its settings so easily? It's a an interesting
speculation. First, let me clarify what I mean by a Tuner's input
terminal and its output terminal. Considering that a tuner handles
transmitted power in one direction only, we should refer to its
"input" side as the port that connects to the transmitter and its
"output" port as the one connecting to the antenna or feedline.

That agrees with what I interpret your post as suggesting. Therefore,
a 50 ohm termination at the "input" side "should" produce a measured
impedance at the "output" port that is, as you say, the complex
conjugate of the impedance seen looking into the transmission line. I
haven't done a rigorous analysis of that configuration, but it
certainly seems reasonable and correct. It would, indeed be an optimum
way of inferring the impedance that the original poster is trying to
measure.

I see nothing wrong with your suggestion and would recommend it.

I also see no reason to do any of that as it would be just as easy to
measure the transmission line input impedance directly - as you said.

It's amazing how much good stuff comes out of the woodwork when people
are interested in their hobby and interested in learning.

Thanks,

Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
w9dmkatcrosslinkdotnet
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html