On 1/29/2014 6:20 PM, amdx wrote:
On 1/29/2014 4:12 PM, Fred Abse wrote:
Lets look at what you have:

You have voltage/current=3350 ohms. That is the *magnitude* of the
impedance, at an angle of 23.5 degrees, current lagging.

That's 3350 angle 23.5 ohms.

We now do a polar to rectangular conversion on that, giving:

3072 +j1335 ohms.

Good, agreement with John S.

3072 seems way too high for the loss component, 1335 ohms is 55
microhenries,at 3.85MHz.

Everyone agrees the loss component is to high. Oh, except me. :-)
I think I have stated, I thought the L would be higher than the R.
That's not what I'm measuring.
I have no experience in ferrite losses, and no education regarding
losses in ferrite. But I think my measurement are in the ballpark.


One thing I suggest is that you do the whole thing again, without, and
then with, the "beads". That way, you can eliminate propagation delays.

I'll try another piece of RG-58/U, I can't get the ferrite of the cable
without cutting off a PL259.

This evening I'll wind a 55uH coil and find a 3,072 resistor. I'll put
these in series and see how it measures compared to my lossy ferrites
beads on a cable.

I already know this measures about 6% high, probably because of the
sense resistor.
Thanks, Mikek


Well, I found the 6% is actually the difference between my scope
probes. That's only my first problem.
I measured a 55uH inductor and 3090 ohm resistor in series, 3.85MHz
and got 2778 ohms 19.9* phase difference.
The calculated numbers are Z = 3,364 and I don't know how to calculate
the phase angle.
Later I'll check this at 100kHz and so if strays are causing errors.
Mikek
PS, I should have some new probes tomorrow.