Jim,
My network analyzer will let you choose Z0 (characteristic or system
impedance), but I never move it off 50 ohms because I'm almost always
working with 50 ohm systems. In the event I have to work with another
impedance, since most of the time all I'm looking for is a "notch" or
"dip" the calculations aren't important.
What I'm hearing so far is don't bother with a GDO, it isn't going to
add any value to my toolbox over what I've already got, is that about
right?
Thanks,
Jeff/KD4RBG
---- Original message ----
>Date: Thu, 20 Mar 2008 16:33:55 -0700
>From: Jim Lux <jimlux@earthlink.net>
>Subject: Re: [TowerTalk] Using a dip meter
>To: Jeff Carter <towertalk@hidden-valley.com>
>Cc: towertalk@contesting.com
>
>Set it up to measure S11, then run
>your coax up to a coupling network of some sort. In theory, you'd want
>a transformer to transform the 50 ohms to whatever the loop resonant R
>would be, but in reality, since you're going to be using loose coupling,
>that will set the magnitude. I've used some turns of magnet wire on a
>BNC connector (and you can add and remove turns by hand) You'll see the
>bump in S11 magnitude at the resonant frequency of the system under test.
>
>(of course, the VNA's probably not handheld. Anritsu has a handheld
>(2hands) device that does this sort of thing, though, if you have a few
>tens o'kilobucks laying around. It's pretty neat)
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|