On 1/28/2014 2:26 PM, Jeff Liebermann wrote:
On Tue, 28 Jan 2014 13:03:35 -0600, 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.

Measure it again. That's an awfully high resistance for a piece of
coax cable of any length. Knowing the type of coax and the length
would be handy. Hopefully, you're not measuring the resistance of
teh broken pot cores. That won't work.

It is a lot. But when I put it together 15 years ago, I seem to
remember about 4000 ohms.
No, I'm measuring shield end to end.
Here's a picture, maybe that will give you a different opinion.
http://s395.photobucket.com/user/Qma...40099.jpg.html


* 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.

The inductance of gapped and non-gapped ferrites are quite different.

For sure, but I didn't care, I just wanted to see how it would act
when I put RG-58u (said 59 before, wrong) thru a bunch of cores.

Check to see if the inductance moves when you move the coax. Also,
RG-59/u is not the best coax on the planet. Try to find some RG-6/u
instead.

You will see in the picture I stabilized it and tapped the whole
thing.
The center hole is not big enough for RG-6/u.

You might want to read through these papers on ferrites (especially
the first):
http://www.audiosystemsgroup.com/K9YC/K9YC.htm

Will do.

When I did this I was thinking about choke baluns hams use on
coax driving antennas.
The whole think is just a curiosity.
Thanks, Mikek