On 1/28/2014 9:51 PM, Jeff Liebermann wrote:
On Tue, 28 Jan 2014 20:34:21 -0600, amdx wrote:

Not sure where we have disagreement, do you disbelieve the 3,350ohms at
3.58MHz?

Yep. I am a heretic. You stated:
"I have measured the R at 3.85MHz, It is 3,350 ohms"
From where to where did you measure 3.35K, presumably with an ordinary
ohms-guesser?

The cable is 12 ft long with a PL259 on each end. I plugged each PL259
into an SO239 panel mount connectors. I then drove 2ma of current
through the shield from panel mount connector to panel mount connector
in series with a 100 ohm resistor. I measured the voltage across the
resistor and calculated the current. This was done at 3.58MHz.
The input voltage was divided by the current to get the impedance.

btw, at one point I took a measurement and got around 800 ohms, took my
a second to figure out I had lowered my frequency to 350 kHz.

Reread, (or read) my response (3:17pm) to Wimpie about my setup and
look at the pictures, I think I laid it out pretty clearly. I was
impressed when I first started using the "setup". Simple, obvious idea,
but the strays need to be worked to a minimum. The "setup" is cheap and
simple and I'd like to refine for those that have a scope and frequency
generator but no other way to measure complex impedances.


If I short one end shield to center pin, and measure the other end
would that double impedance?
I'm going to find out.

It's like winding two turns on a toroid in opposite directions. The
inductances cancel and you get zero inductance. Replace the coax
cable with a single loop length of wire and see if it makes more
sense. Only turns that go AROUND the toroid in the same direction
provide useful inductances.

You're correct, I measured very low ohms and no phase difference.

Curious to hear your input on the "setup" and what else I can do to
give you more confidence in my measurement, OR fix my "setup".

I'll measure some known parts tomorrow evening.

Thanks Jeff.