On Wed, 05 Mar 2008 02:29:19 -0600, Webmaster wrote:

[snippity]

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[snippity]

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I'm working on a project that requires measuring of impedance on a coax
antenna feed: resistive, reactive components. Ideally I will need a
plus/zero/minus voltage for reactive direction/magnitude.

The absolute value of the reactance is not of prime concern (will drive
servo motors, but I need to know capacitive or inductive, and when it is at
zero. I have serveral circuits to accomplish this, but they are quite
involved. The object of this project is not to design a new Antenna
Analyzer, but it is a component, that I would like to make as simple as
possible, with accomplishing the stated goals.

I would appreciate any references/articles/links/ideas that you may know of.

Thanks,
Emil
w9nm at
sbcglobal dot
net

Sbc News wrote:
I'm working on a project that requires measuring of impedance on a coax
antenna feed: resistive, reactive components. Ideally I will need a
plus/zero/minus voltage for reactive direction/magnitude.

Take a look at the schematics for the LDG or SGC autotuners. They both
have some form of bridge circuit, and the SGC detects the sign of the
relative phase.


One can use, for instance, the phase frequency detector from a PLL (i.e.
a JK flipflop appropriately wired) to compare the relative phase of
forward and reflected powers from a bridge. (and, for your application,
you don't need a calibrated bridge..)

For HF purposes, there's a lot of digital circuits out there that are
fast enough, and for the usual antenna tuner kind of application, you've
got enough signal.



The absolute value of the reactance is not of prime concern (will drive
servo motors, but I need to know capacitive or inductive, and when it is at
zero. I have serveral circuits to accomplish this, but they are quite
involved. The object of this project is not to design a new Antenna
Analyzer, but it is a component, that I would like to make as simple as
possible, with accomplishing the stated goals.

I would appreciate any references/articles/links/ideas that you may know of.

Thanks,
Emil
w9nm at
sbcglobal dot
net