I have question about R L Mathematics

[amdx]

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.

 

[amdx]

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 <nojunk@knology.net> 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

 

[John S]

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

 

[George Herold]

On Tuesday, January 28, 2014 2:03:35 PM UTC-5, 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

Hi Mike, I'm confused (which is normal). Both the shield and center conductor are going through the same bead? In theory with 'perfect' coax this should do nothing (All the E/M fields are contained within the coax.) But maybe you have a different setup. And of course coax is not perfect.
To measure L, I'd pick a know capacitance and then find where it resonates. (I guess a bit harder with coax with already some C in there... but maybe pick a C much bigger than the capacitance of the coax.)

George H.

* 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.

 

[amdx]

On 1/28/2014 10:29 PM, Jeff Liebermann wrote:

On Tue, 28 Jan 2014 21:05:07 -0600, amdx <nojunk@knology.net> wrote:

Nope, almost zero ohms, shorting one end and measuring center to shield
on the other end at 3.58MHz.
To reiterate, measuring this 12ft of RG58/u with 42 half cores of 3B7
(material) (size 3019) slide over the coax, shows an impedance of about
3,350 ohms with an inductive phase angle of 22.5*.

You previously said "I have measured the R at 3.85MHz, It is 3,350
ohms." Now, you change it to impedance. Please make up your mind.

I did say that, I wrongly thought it was 3,350 ohms with 22.58 phase
shift, implying some as yet unknown amount of inductance. If you follow
the thread, I immediately followed my own thread with,
"The Total impedance is 3,350 ohms, this includes R and L."
I apologize for my screwups making it difficult for anyone reading to
follow along.
However, if I new what I was doing, I wouldn't be posting a question.

However, I screwed up in my previous message. I forgot that you're
working with coax cable, where the center wire is shielded from the
effects of the inductors by the outside shield. So, you'll see the
equivalent of what you would get with a single wire going through all
the cores.

Yes, a loss resistance and inductance of one turn.

> Got an Al value for a single core?

I believe it is 9660 +/- 25%. This is for two core sandwiched. However,
does that have any use for calculations? I'm using the core in a manner
that is not normal. I don't remember how I placed the core halves, face
to face, back to back, mixed?

I can't find a data sheet on the
new

Ya, I found an exchange where I was asking for
that info back in back in 2007.
I got it privately from a friend with an old catalog.

>and useless Ferroxcube web pile.

I thought the pile was ok, it just didn't have the 3B7,
must be old and obsolete.

Here's roughly how I would do it
if I had the Al of your cores.

L(mH) = Al * N^2 * n / 10^6

N = number of turns, which in this case is 1.
n = number of cores, which in this case is 42.

Xl = 2 * Pi * f * L
Xl = 6.28 * 3.85*10^6 * L(mH)/10^3


The DC resistance is so small that it can be neglected.


You obtained a 22.5 degree phase angle which might be the capacitance
of the coax cable.

The phase is inductive, E leads I.

I don't really know where it came from. That
angle would normally come from a resistance in the loop, but the coax
is nearly zero ohms. If there were any resistance, the phase angle
would be:
phase-angle = arctan(Xl/R)
If it is the cazapitance:

For RG-59/u 16.2 pf per foot for 12 ft would be 203 pf.
Xc = 1 / (2 * Pi * f * C)
Xc = 1 / (6.28 * 3.85*10^6 * 200*10-12)
Xc = 207 ohms

The vector sum of the reactances should give you the impedance.

Now, all you have to do is either supply a measured inductance or find
the Al of your cores.

I thought I had, but apparently it was in my secret code.
John S calculated "Therefore, R = 3072 ohms and X = 1336 ohms
As a sanity check, Z = sqrt(R^2 + X^2) = 3,350"

So if X = 1336 ohms at 3.85 MHz inductance is 55uH.

I'm a little surprised, I would have thought the reactance would have
been higher than the resistance.

Are you sure it's 3.85MHz and not the more common 3.58MHz? I smell a
transposition of numbers here.

I picked 3.85MHz to be in the 80 meter ham band.

The whole system is touchy, putting your hand on the coax changes the
current shown on the scope, also reorienting the coax will change the
current.

That's mostly because of the broken cores causing Al to change as they
move. More duct tape.

Yes and more, just putting your hand by the coax causes the current
to change.

What are your thoughts, Jeff specifically and anyone else.

My thoughts are that I'm going to throw up. However, it's not your
questions or academic exercises. It's the junk food I excavated from
the back of the office fridge. Time to recycle everything.

I had to stop eating cashews last night, I was moving in that green
feeling direction. Time to get ready for work.

Thanks, Mikek

 

[Jeff Liebermann]

On Wed, 29 Jan 2014 07:08:25 -0600, amdx <nojunk@knology.net> wrote:

> However, if I new what I was doing, I wouldn't be posting a question.

If I knew what you were trying to do, I wouldn't be asking you
questions.

Got an Al value for a single core?

I believe it is 9660 +/- 25%. This is for two core sandwiched. However,
does that have any use for calculations? I'm using the core in a manner
that is not normal. I don't remember how I placed the core halves, face
to face, back to back, mixed?

Argh. It's a pot core that's designed to have all its turns inside
the two halves of the pot core on a bobbin. What you've apparently
done is used it in a non-standard and unpredictable manner by shoving
a wired through the hole normally reserved for either a ferrite
adjustment slug, or a nylon mounting screw. The spec sheet Al value
is worthless.

However, all is not lost. You can take 1/2 of a core, shove a wire
through the hole, and measure the inductance. That's inductance as in
uH not the calculated reactance or guessed impedance. I presume that
there are 42 half-cores so just multiplying the measured value by 42
will give a tolerable approximation of the total inductance. You
could also measure the total inductance of all 42 cores to see if that
really works.

Note that I'm suggesting that you measure the inductance with a single
wire going through the cores, and not with a loop produced by shorting
one end of the coax cable. That takes some of the mystery out of the
measurements. You can see what shorting one end does later.

Ya, I found an exchange where I was asking for
that info back in back in 2007.
I got it privately from a friend with an old catalog.

I have several old Ferroxcube catalogs from the 1970's and 1980's.
You can't have them.

The vector sum of the reactances should give you the impedance.

Now, all you have to do is either supply a measured inductance or find
the Al of your cores.

I thought I had, but apparently it was in my secret code.
John S calculated "Therefore, R = 3072 ohms and X = 1336 ohms
As a sanity check, Z = sqrt(R^2 + X^2) = 3,350"

So if X = 1336 ohms at 3.85 MHz inductance is 55uH.

I'm a little surprised, I would have thought the reactance would have
been higher than the resistance.

The only thing I can be sure of here is that the resistive component
is *NOT* 3000 ohms because it can be directly measured with an
ohms-guesser. The number is (obviously) wrong because nowhere in your
circuit is anything resembling a resistor of that high a value. If
you work backwards and assume a DC resistance of zero, then Z = Xl.
I'm still not sure what's causing the 22 degree phase angle. My best
guess(tm) is that it's the capacitance of the coax cable, but that
should have disappeared when you shorted one end of the coax. Dunno.

Yes and more, just putting your hand by the coax causes the current
to change.

My hand is firmly attached to my arm and is nowhere near your setup.
Perhaps you meant your hand?

I had to stop eating cashews last night, I was moving in that green
feeling direction. Time to get ready for work.

I compounded my culinary error by eating about 1/3 a salted dark
chocolate bar before going to bed. It's now 7AM and I've had about 3
hours of erratic sleep due to the caffeine overdose. I've done this
before and should have known better, but it was sooooooo good. At
least I'm now caught up on paying my bills and reading various
reports. My next challenge will be to see if I can drive to the
office without falling asleep.

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

 

[amdx]

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

On Wed, 29 Jan 2014 07:08:25 -0600, amdx <nojunk@knology.net> wrote:

However, if I new what I was doing, I wouldn't be posting a question.

If I knew what you were trying to do, I wouldn't be asking you
questions.

Got an Al value for a single core?

I believe it is 9660 +/- 25%. This is for two core sandwiched. However,
does that have any use for calculations? I'm using the core in a manner
that is not normal. I don't remember how I placed the core halves, face
to face, back to back, mixed?

Argh. It's a pot core that's designed to have all its turns inside
the two halves of the pot core on a bobbin. What you've apparently
done is used it in a non-standard and unpredictable manner by shoving
a wired through the hole normally reserved for either a ferrite
adjustment slug, or a nylon mounting screw. The spec sheet Al value
is worthless.

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.

However, all is not lost. You can take 1/2 of a core, shove a wire
through the hole, and measure the inductance. That's inductance as in
uH not the calculated reactance or guessed impedance. I presume that
there are 42 half-cores so just multiplying the measured value by 42
will give a tolerable approximation of the total inductance. You
could also measure the total inductance of all 42 cores to see if that
really works.

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.

>You can see what shorting one end does later.

I already did that, zero inductance or resistance.

Ya, I found an exchange where I was asking for
that info back in back in 2007.
I got it privately from a friend with an old catalog.

I have several old Ferroxcube catalogs from the 1970's and 1980's.
You can't have them.

Do you need any potcores?

The vector sum of the reactances should give you the impedance.

Now, all you have to do is either supply a measured inductance or find
the Al of your cores.

I thought I had, but apparently it was in my secret code.
John S calculated "Therefore, R = 3072 ohms and X = 1336 ohms
As a sanity check, Z = sqrt(R^2 + X^2) = 3,350"

So if X = 1336 ohms at 3.85 MHz inductance is 55uH.

I'm a little surprised, I would have thought the reactance would have
been higher than the resistance.

The only thing I can be sure of here is that the resistive component
is *NOT* 3000 ohms because it can be directly measured with an
ohms-guesser.

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?

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

If you work backwards and assume a DC resistance of zero, then Z = Xl.
I'm still not sure what's causing the 22 degree phase angle. My best
guess(tm) is that it's the capacitance of the coax cable, but that
should have disappeared when you shorted one end of the coax. Dunno.

It's inductive.

Yes and more, just putting your hand by the coax causes the current
to change.

My hand is firmly attached to my arm and is nowhere near your setup.
Perhaps you meant your hand?

LOL, you're right, it was my hand.

I had to stop eating cashews last night, I was moving in that green
feeling direction. Time to get ready for work.

I compounded my culinary error by eating about 1/3 a salted dark
chocolate bar before going to bed. It's now 7AM and I've had about 3
hours of erratic sleep due to the caffeine overdose. I've done this
before and should have known better, but it was sooooooo good. At
least I'm now caught up on paying my bills and reading various
reports. My next challenge will be to see if I can drive to the
office without falling asleep.

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

 

[amdx]

On 1/29/2014 9:09 AM, George Herold wrote:

On Tuesday, January 28, 2014 2:03:35 PM UTC-5, 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

Hi Mike, I'm confused (which is normal). Both the shield and center conductor are going through the same bead?
In theory with 'perfect' coax this should do nothing (All the E/M fields are contained within the coax.)

Most of my info was measuring the impedance of the shield through the
ferrite, no other connections. It was R=3k XL=1.2k approx.
I did do a test with one end shorted, looking into the other end,
and you are correct, it measured zero inductance and zero ohms.

>But maybe you have a different setup.
Yea, my "setup" is different.
I describe it with pictures after Wimpie ask. Time was 3:17 on the 28th.

And of course coax is not perfect.

To measure L, I'd pick a know capacitance and then find where it resonates.
(I guess a bit harder with coax with already some C in there... but maybe pick a C much bigger than the capacitance of the coax.)

I can revisit. I did bring it near 0* phase with 3700pf, but it was
not sharp and I should have added more capacitance to pass through
resonance for a better understanding.
"Not sharp" probably because of the 3k Resistance.

George H.



* 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.

 

[Fred Abse]

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

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

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

I want to calculate the impedance of the reactance.

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

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.

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

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.


--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[amdx]

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/Qmavam/media/FerriteBeads_zpsa2340099.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

 

[Jeff Liebermann]

On Wed, 29 Jan 2014 09:45:51 -0600, amdx <nojunk@knology.net> 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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[amdx]

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.

 

[amdx]

On 1/29/2014 10:26 PM, Jeff Liebermann wrote:

On Wed, 29 Jan 2014 09:45:51 -0600, amdx <nojunk@knology.net> 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 jeffl@cruzio.com 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

 

[Baron]

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.

 

[John S]

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

 

[Fred Abse]

On Wed, 29 Jan 2014 18:20:16 -0600, amdx wrote:

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

Don't use those things, they're horrible. Designed around 1939, should
have disappeared in 1940, attributed to a guy called Quackenbush. I think
he was actually Groucho Marx ;-)

Soldering direct would be better, in this case.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[Fred Abse]

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.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[John S]

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?

 

[amdx]

On 1/30/2014 1:14 PM, John S wrote:

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

Hi John,
My address is good.
These are 2" ceramics, 1/16", they resonate around 1.2MHz as I recall.
We bonded them to 1/16" aluminum for approximately a 660kHz transducer.
We drove them at antiresonance, where they measured around 20 ohms.
We drove them continuous at 250 watts in an ice bath and 1000 watt pulsed.
Send me an email.
Mikek