"Jeff Liebermann" wrote in message
...
On Sun, 18 Oct 2009 13:41:23 -0500, "amdx" wrote:

Hi all,
I saw a site where a fellow designed a unit to measure impedance at 2.4
ghz, for use on wifi antennas. I don't recall if it was return loss or
impedance.
It gave detailed instructions on how to build and he also had ready built
units
for sale.
I think it was a ham that designed the unit. I also think he was not in
the
states, possibly a P or PY call sign, but the memory is not good!
Any help would be appreciated.
Thanks, Mike


This is a copy of my reply to your duplicate posting to
alt.internet.wireless. Please don't do that again:


Sorry, I thought about putting it on these other groups just as I hit send.


This one?
http://pe2er.nl/wifiswr/index.htm
or one of these:
http://www.qsl.net/n9zia/wireless/appendixF.html

What I do is use a return loss bridge as in:
http://www.qsl.net/n9zia/wireless/pics/rtrn_loss_bridge.png
I've built several out of chip resistors and junk parts. I have one
that works well up to about 8GHz. Great for testing antennas. That's
what's inside a Telonic Rho-tector (which can usually be found on eBay
for cheap). A few models go up to 2.4Ghz.

You'll also *might* need a microwave load or three. 50 ohms for a
reference, but also some other known values for calibration.

The problem is that you'll need an RF sweep generator to use this
effectively. It's also not a VNA (vector network analyzer) so it
won't tell you if any reactance is capacitive or inductive.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558