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.

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.


I had a thought, I measured the R by dividing Voltage by Current.
So that means, my current was limited my the L also. The Total impedance
is 3,350 ohms, this includes R and L.

Mikek

In rec.radio.amateur.antenna 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.

The real resistance should not change with frequency so just measure it
with an ohmmeter.

Total impedance is the square root of the sum of the squares of resistance
and reactance.

The phase angle will tell you if the reactance is inductive or capacitive.


--
Jim Pennino

Hi, Mike -

On 1/28/2014 1:14 PM, amdx wrote:
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 will assume that Z is 3350 ohms at 3.85MHz.

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.

The impedance of the reactance (alone) IS the reactance (itself).

Can anyone solve this for me?

I will try.

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?

We do (based on your numbers)...

Z = 3350 @ 23.5 degrees.

R = Z * COS(23.5) and
X = Z * SIN(23.5)

Therefore, R = 3072 ohms
and X = 1336 ohms

As a sanity check, Z = sqrt(R^2 + X^2) = 3350

Good!

HTH,

John S


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.


I had a thought, I measured the R by dividing Voltage by Current.
So that means, my current was limited my the L also. The Total impedance
is 3,350 ohms, this includes R and L.

Mikek

El 28-01-14 20:03, amdx escribió:
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.

Did you actually measured R (say Re(Z) ) , or |Z|?

Can you provide us some info on your setup?

--
Wim
PA3DJS
www.tetech.nl
Please remove abc first in case of PM

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 measureing the resistance of
teh broken pot cores. That won't work.

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

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 1/28/2014 2:25 PM, Wimpie wrote:
El 28-01-14 20:03, amdx escribió:
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.

Did you actually measured R (say Re(Z) ) , or |Z|?

I measured the voltage, the current and the phase relationship.


Can you provide us some info on your setup?


I can, it might turn into a word war, but have used it very
successfully 100s of times at 600kHz, I'm not sure of the accuracy
at 10 MHz. But with time I will refine it as needed.

Here's a diagram of the setup.
http://s395.photobucket.com/user/Qma...awing.jpg.html
Ignore the green lines and print for now.

Here's the board with scope probes attached.
http://s395.photobucket.com/user/Qma...notes.jpg.html
(Note the curly Qs holding the probes, very useful for measurements were
the leads cause ringing.)

You connect a frequency generator and "Device to be Measured", adjust
the frequency, and set the output level. I like to set the voltage at
1vpp, but it doesn't matter.
On the scope you will see the voltage and the current as measured
across the sense resistor.
Say for your current you have 5 units pp on .02v scale, across a
100 ohm sense resistor. 5 x .02 / 100 = 0.001 amps pp. Then 1vpp /
0.001amps pp = 1000 ohms. Your 100 sense resistor is in series, so must
be subtracted out, 1000 - 100 = 900 ohms. You can use the scope to see
the phase.
You can drop the pp, the numbers all come out the same.

Now the fun part.

I original used a device like this when I was measuring the R and C
of bonded piezos in water. That brings me to the green lines in the
first drawing, where it shows the capacitor, I had a variable inductor.
I would adjust the inductor to tune out the capacitance of the piezo,
(set the inductor so the scope shows zero phase difference.) I would
then use the scope readings to calculate the R of the piezo. Then I
would short the piezo connection and use the scope readings to calculate
the impedance of the inductor, which is the same as the capacitance of
the piezo with reverse sign.
Then the higher functioning brains would calculate transformer and
inductors for the amplifier.
Any questions?
Learned this from Henry.
Mikek

On 1/28/2014 2:12 PM, John S wrote:
Hi, Mike -

On 1/28/2014 1:14 PM, amdx wrote:
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 will assume that Z is 3350 ohms at 3.85MHz.

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.

The impedance of the reactance (alone) IS the reactance (itself).

Can anyone solve this for me?

I will try.

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?

We do (based on your numbers)...

Z = 3350 @ 23.5 degrees.

R = Z * COS(23.5) and
X = Z * SIN(23.5)

Therefore, R = 3072 ohms
and X = 1336 ohms

As a sanity check, Z = sqrt(R^2 + X^2) = 3350

Good!

HTH,

John S

Thank you John.
Mikek

On 1/28/2014 1:32 PM, wrote:
In rec.radio.amateur.antenna 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.

The real resistance should not change with frequency so just measure it
with an ohmmeter.

I'm not sure, it might change with frequency, this is a ferrite around a
wire, so the ohm meter won't work. It's loss in the ferrites.

Total impedance is the square root of the sum of the squares of resistance
and reactance.

The phase angle will tell you if the reactance is inductive or capacitive.

Yup, Eli the Ice man.
Mikek

On 1/28/2014 3:18 PM, amdx wrote:
On 1/28/2014 2:12 PM, John S wrote:
Hi, Mike -

On 1/28/2014 1:14 PM, amdx wrote:
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 will assume that Z is 3350 ohms at 3.85MHz.

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.

The impedance of the reactance (alone) IS the reactance (itself).

Can anyone solve this for me?

I will try.

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?

We do (based on your numbers)...

Z = 3350 @ 23.5 degrees.

R = Z * COS(23.5) and
X = Z * SIN(23.5)

Therefore, R = 3072 ohms
and X = 1336 ohms

As a sanity check, Z = sqrt(R^2 + X^2) = 3350

Good!

HTH,

John S

Thank you John.
Mikek


It makes me feel good that I could assist. So, I thank you as well.

Cheers,
John S