I have question about R L Mathematics
 

On 1/29/2014 4:12 PM, Fred Abse 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. I have also measured
the phase shift, voltage leading by 17ns. The period of 3.85Mhz is 260ns.

I'm not sure I understand what you're trying to measure. I assume that
it's the effect of the "beads" on the inductance of the outer conductor,

That is correct.

in which case, 3350 ohms looks way OTT. No pot core material I know of is
*that* lossy.


That's what everyone seems to think. I'm the odd man out.
If you haven't looked at the picture, here it is. The ferrite is 18
inches long. That is a quarter in front.
http://s395.photobucket.com/user/Qma...40099.jpg.html



How long is the coax sample? 17ns is the delay of approx. 5 meters of wire
at 3.85MHz, without any inductive loading.

It is 11 ft long.

You did connect to the outer conductor at both ends, didn't you.

Yes, outer conductor connected at both ends. To different inputs of the
measuring device.

Preferably short inner to outer, at both ends.

That I have not done. I'll try that.
........

.......

OK, I'm back. Shorting the center pin to the shield, (at both ends)
made absolutely no difference in the magnitude or phase of the measurement.



I want to calculate the impedance of the reactance.

LOL, I had to go back and see if I said that.

Now I'll say what I meant.
I want to know the magnitude in ohms of the reactance.
John S already solved that for me, thanks.
He knows how to solve for what I want, not what I ask for. :-)


There's no such thing. Reactance is merely the imaginary part of a
(complex) impedance.

Already restated.


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?

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

I have question about R L Mathematics
 

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.

I have question about R L Mathematics
 

On Wed, 29 Jan 2014 09:45:51 -0600, amdx wrote:

On 1/29/2014 9:04 AM, Jeff Liebermann wrote:

I have a feeling you didn't look at any of my pretty pictures, I think
at least one layer of fog should have dissipated if you did.
They're really pretty.

http://s395.photobucket.com/user/Qmavam/media/TheBoardwithnotes.jpg.html
http://s395.photobucket.com/user/Qmavam/media/TheBoardDrawing.jpg.html
I clicked, I looked, I saw, I failed to understand, I blundered
onward. What did I miss?

You really want a vector impedance meter:
http://www.ebay.com/itm/181276724052
Yeah, I know it's an antique. There are probably much better models
available today, but not at the price. I had one at a previous
employer and used it for measuring almost everything. 0.5 to 110 Mhz.
I've been looking for a broken one (because I blew up the one I was
using often enough to be familiar with the repair procedures) but
can't seem to find one in my price range (i.e. free). Make sure it
comes with the probe and power cord as both are difficult to find.

Note that I'm suggesting that you measure the inductance with a single
wire going through the cores,

I'm doing that now, only with 42 halves. I can try it with one, but I
question with my "setup" will resolve that inductance.

Never mind. You won't see it. At the time, I was trying to correlate
the measured value with the theoretical Al. However, since the cores
are not being used in the normal manner, that's not going to work or
yield any useful results. Might as well measure the whole string at
once.

Do you need any potcores?

No thanks. I gave smoking the stuff in college. You might be able to
sell them in Colorado.

Since you have used "ohms-guesser" I guess I need to ask, What is that?
and does it use ac or dc for the measurement?

An ohms-guesser(tm) is a Harbor Freight DVM or equivalent. Usually
sells for $5 or less. Capable of producing wrong values to at least 3
1/2 digit accuracy. I usually have several available for the
inevitable visitors that roll into my parking lot wanting to borrow a
meter to fix their vehicle electrical system. Ohms-guessers use DC
current to measure resistance. There is also the volts-guesser and
amps-guesser which offer similar features and lack of accuracy.

The number is (obviously) wrong because nowhere in your
circuit is anything resembling a resistor of that high a value.

I'm sure you understand that ferrite beads on a transistor lead, show
up as a resistive and inductive. Why is this different?
Here's a pdf with a graph page 4 right side showing R, X, and Z.
Hand picked to show what I want it to! Although I should have secretly
altered the frequency range.
http://www.vishay.com/docs/ilb_ilbb_enote.pdf

ARGH! I goofed. I forgot how ferrite really work and was assuming
that it represented a pure inductance. Please ignore everything I
wrote about the resistive component. I tried to find a reactance vs
frequency graph for the 3B7 material and failed. Maybe later tonite.
I'm buried in broken machines and an office in desperate need of
untrashing. Thanks (grumble).

Incidentally, consider yourself off the hook for the MFJ-1800 yagi
fiasco if you promise not to tell anyone how badly I messed up here.

I'm in Fl. where people are acting like the end is near.

Huh? Are they expecting Florida to sink into the ocean under the
added weight of the snow?

We are slightly below freezing and businesses are closing, schools out.
The weather men are have fits of frenzy. If I was back in Michigan, we
would be happy it got warmer, because we were getting tired of starting
the car at 7* in 8 inches of snow.
Mikek

In the People's Republic of Santa Cruz, it has been mostly 60-70F
highs and 35-45F lows for most of the alleged winter. Quite pleasant
and comfortable. The problem is that we've had less than an inch of
rain this season, where normal would be about 15-20 inches by this
date. The forest looks awful with dead trees and shrubbery
everywhere. Looks like we're going to have a severe drought here.
Even worse is the lack of snow for skiing. Right now, I could use
some snow or rain.

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

I have question about R L Mathematics
 

On Wednesday, January 29, 2014 6:20:16 PM UTC-6, amdx wrote:
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.

A coil of that large size will exhibit transmission line characteristics that will render the lumped-circuit model inaccurate because the current into the coil will not be equal to the current out of the coil. Better to use the distributed network model which is closer to Maxwell's equations. Here is an inductance calculator that will yield more accurate results for coils that are greater than ~15 degrees long electrically. Using the axial propagation factor (Beta) of the the coil, one can calculate how many degrees it occupies. Then using the characteristic impedance (Z0) of the coil, one can analyze the circuit like a transmission line using the distributed network model. If you will describe the characteristics of the coil in detail (total turns, length, wire size, etc.) I will do the analysis for you.
--
73, Cecil, w5dxp.com

I have question about R L Mathematics
 

On Thursday, January 30, 2014 6:41:53 AM UTC-6, W5DXP wrote:
Here is an inductance calculator that will yield more accurate results for coils that are greater than ~15 degrees long electrically.

Sorry, I forgot to post the URL of the inductance calculator:

http://hamwaves.com/antennas/inductance.html

I have question about R L Mathematics
 

On 1/29/2014 10:26 PM, Jeff Liebermann wrote:
On Wed, 29 Jan 2014 09:45:51 -0600, amdx wrote:

On 1/29/2014 9:04 AM, Jeff Liebermann wrote:

I have a feeling you didn't look at any of my pretty pictures, I think
at least one layer of fog should have dissipated if you did.
They're really pretty.

http://s395.photobucket.com/user/Qmavam/media/TheBoardwithnotes.jpg.html
http://s395.photobucket.com/user/Qmavam/media/TheBoardDrawing.jpg.html
I clicked, I looked, I saw, I failed to understand, I blundered
onward. What did I miss?

Probably not much. :-(
Very simple concept, Measuring current by use of a sense resistor.
Then comparing voltage to current to get impedance.


You really want a vector impedance meter:
http://www.ebay.com/itm/181276724052

I have recently acquired an HP 3570A Network analyzer and a 3330B
synthesizer that are GPIB connected to a computer with custom software.
It has not been powered for at least 10 years. The only problem I know
about is the computer cmos battery most likely has failed.
I've had it a couple months now and have not got it setup or attempted
any use. I need to figure out what to do about the computer first. I
don't have the original software disc, so I need to copy the program
first thing.


Yeah, I know it's an antique. There are probably much better models
available today, but not at the price. I had one at a previous
employer and used it for measuring almost everything. 0.5 to 110 Mhz.
I've been looking for a broken one (because I blew up the one I was
using often enough to be familiar with the repair procedures) but
can't seem to find one in my price range (i.e. free). Make sure it
comes with the probe and power cord as both are difficult to find.

Note that I'm suggesting that you measure the inductance with a single
wire going through the cores,

I'm doing that now, only with 42 halves. I can try it with one, but I
question with my "setup" will resolve that inductance.

Never mind. You won't see it. At the time, I was trying to correlate
the measured value with the theoretical Al. However, since the cores
are not being used in the normal manner, that's not going to work or
yield any useful results. Might as well measure the whole string at
once.

Do you need any potcores?

No thanks. I gave smoking the stuff in college. You might be able to
sell them in Colorado.



Since you have used "ohms-guesser" I guess I need to ask, What is that?
and does it use ac or dc for the measurement?

An ohms-guesser(tm) is a Harbor Freight DVM or equivalent. Usually
sells for $5 or less. Capable of producing wrong values to at least 3
1/2 digit accuracy. I usually have several available for the
inevitable visitors that roll into my parking lot wanting to borrow a
meter to fix their vehicle electrical system. Ohms-guessers use DC
current to measure resistance. There is also the volts-guesser and
amps-guesser which offer similar features and lack of accuracy.


You may have figured out, I'm not using this type of ohms guesser.

The number is (obviously) wrong because nowhere in your
circuit is anything resembling a resistor of that high a value.

I'm sure you understand that ferrite beads on a transistor lead, show
up as a resistive and inductive. Why is this different?
Here's a pdf with a graph page 4 right side showing R, X, and Z.
Hand picked to show what I want it to! Although I should have secretly
altered the frequency range.
http://www.vishay.com/docs/ilb_ilbb_enote.pdf

ARGH! I goofed. I forgot how ferrite really work and was assuming
that it represented a pure inductance. Please ignore everything I
wrote about the resistive component. I tried to find a reactance vs
frequency graph for the 3B7 material and failed. Maybe later tonite.
I'm buried in broken machines and an office in desperate need of
untrashing. Thanks (grumble).


Incidentally, consider yourself off the hook for the MFJ-1800 yagi
fiasco if you promise not to tell anyone how badly I messed up here.


My deed here has been accomplished, I now officially close this thread.
yippee, yahoo, hallelujah, praise be to any omnipotent powers.


I'm in Fl. where people are acting like the end is near.

Huh? Are they expecting Florida to sink into the ocean under the
added weight of the snow?

We are slightly below freezing and businesses are closing, schools out.
The weather men are have fits of frenzy. If I was back in Michigan, we
would be happy it got warmer, because we were getting tired of
starting the car at 7* in 8 inches of snow.
Mikek

In the People's Republic of Santa Cruz, it has been mostly 60-70F
highs and 35-45F lows for most of the alleged winter. Quite pleasant
and comfortable. The problem is that we've had less than an inch of
rain this season, where normal would be about 15-20 inches by this
date. The forest looks awful with dead trees and shrubbery
everywhere. Looks like we're going to have a severe drought here.
Even worse is the lack of snow for skiing. Right now, I could use
some snow or rain.

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


I have found through some tests and exchanges here that the mechanics of
my "setup" work fine below 1MHz or a little higher. But I think, strays
are causing some problems when I go higher in frequency.
I should get my new probes today and I'll be working at tightening
up the circuit and maybe adding shielding.
I built this "setup" as as duplicate of the one I used, I tried to use
it at higher frequency and I should not have.

When I was working with ultrasonics, our standard frequency was around
660 kHz. We used this daily to characterize piezo transducers to
calculate matching to an amplifier.
I sure wish the company made some money, I really enjoyed that job.

btw, Need any 2" disc piezo ceramic discs 1/16" thick PZT-8 material?
I have a few other sizes also.
Do you know any fun things I could do with them, besides give people
shocks.

Thanks, Mikek

I have question about R L Mathematics
 

Jeff Liebermann scribbled thus:

In the People's Republic of Santa Cruz, it has been mostly 60-70F
highs and 35-45F lows for most of the alleged winter. Quite pleasant
and comfortable. The problem is that we've had less than an inch of
rain this season, where normal would be about 15-20 inches by this
date. The forest looks awful with dead trees and shrubbery
everywhere. Looks like we're going to have a severe drought here.
Even worse is the lack of snow for skiing. Right now, I could use
some snow or rain.


All that rain is over here... Snow threatened :-(

--
Best Regards:
Baron.

I have question about R L Mathematics
 

On 1/30/2014 9:37 AM, Baron wrote:
Jeff Liebermann scribbled thus:

In the People's Republic of Santa Cruz, it has been mostly 60-70F
highs and 35-45F lows for most of the alleged winter. Quite pleasant
and comfortable. The problem is that we've had less than an inch of
rain this season, where normal would be about 15-20 inches by this
date. The forest looks awful with dead trees and shrubbery
everywhere. Looks like we're going to have a severe drought here.
Even worse is the lack of snow for skiing. Right now, I could use
some snow or rain.


All that rain is over here... Snow threatened :-(


We're up to 34*, the icicles are dripping.
Supposed to be 61* tomorrow.
Glad January is about over, maybe February will
be better. The global warming has been brutally
cold this year.
Mikek

I have question about R L Mathematics
 

On 1/30/2014 9:33 AM, amdx wrote:
(snip)

btw, Need any 2" disc piezo ceramic discs 1/16" thick PZT-8 material?
I have a few other sizes also.
Do you know any fun things I could do with them, besides give people
shocks.

Thanks, Mikek

Hi, Mike -

I would like to buy a couple to experiment with and, possibly, learn
something.

How many $ do you want and how do we connect?

Thanks,
John S

I have question about R L Mathematics
 

On 1/30/2014 1:17 PM, Fred Abse wrote:
On Wed, 29 Jan 2014 20:26:16 -0800, Jeff Liebermann wrote:

You really want a vector impedance meter:

He's actually doing what a vector impedance meter does - the hard way.

A vector voltmeter might be of more use in Mike's case. More versatile.


Where is one available and what would it cost?