On 1/28/2014 1:03 PM, amdx wrote:
I have beads* on a coax and want to know the R and the L.
I have measured the R at 3.85MHz, It is 3,350 ohms.
I have also measured the phase shift, voltage leading
by 17ns. The period of 3.85Mhz is 260ns.

I want to calculate the impedance of the reactance.

Can anyone solve this for me?
I would like to see the math, because I want to measure again
at 7.5MHz.

My first step was to find the phase angle, 23.5*.
Do we agree there?

Thanks, Mikek


* it is actually a bit more than beads. Years ago, we were sent a box of
ferrite potcores, the cores arrived broken. I slide 42 broke halves onto
a piece of RG59, and now I'm measuring it.


Hi, Mike -

I have reviewed your pictures and re-read the posts and I have a couple
of new comments.

* I don't know how you verified that your probes are a problem, but I
suggest applying the same signal to both, recording the results,
swapping channels, and see if the problem follows the probes or not. If
the problem follows, it's the probes. If not, it's the scope channels.

* The ll feet of coax alone will cause almost 11ns of delay. Since you
have it coiled on each end, the delay will be more than that. This
leaves us in an even worse situation to explain high R and low L.

* If you, by any chance, have another 11-feet piece of coax without the
cores, try measuring that.

Good luck.

John S