John Smith I wrote:

...

I should have mentioned, in case it escaped your attention, a SW
receiver will serve as freq counter (watch out for harmonics), if you
have patience to hunt the signal ... you can "rough guess" the freq by
the expectations of the expected inductance (type 43, 61, etc. and no.
of turns) and the capacitance used.

JS

Larry Benko wrote:

That is what I thought also Roy but the little L/C meter seems to work
pretty well with low Q inductors. It is not measuring impedance but
measuring a frequency of an inductor and known capacitor in an
oscillator. The Q does change the oscillating frequency but not that
much. As I said before it is super easy to tell the difference between
77/31/43/61 type ferrites. Of course the permeability difference
between those types is a factor of 2 or more so ultra accuracy is not
important. The original question was how to determine what type an
unknown core was and not what impedance it represented at a certain
frequency.

I just grabbed 3 FairRite 59XX003801 torroids (2.4" OD x 1.4" ID x .5")
in 3 materials and measured a single turn with the L/C meter.

Material 61 (u=125) calc. inductance = .173uH, measured = .177uH
Material 43 (u=800) calc. inductance = 1.07uH, measured = .930uH
Material 75 (u=5000) calc. inductance = 6.85uH, measured = 7.39uH

The calculated inductances came from the FairRite catalog. I would say
the "low Q" inductors measured pretty well and the materilas were very
easy to distinguish.

Yep, that's perfectly adequate to distinguish the types. You must have
made the measurements at a pretty low frequency. Type 75 has a Q of 1 at
about a MHz, and 43 at a few MHz, and they drop at higher frequencies.
Will the circuit oscillate with Q that low?

Roy Lewallen, W7EL

Roy Lewallen wrote:


Yep, that's perfectly adequate to distinguish the types. You must have
made the measurements at a pretty low frequency. Type 75 has a Q of 1 at
about a MHz, and 43 at a few MHz, and they drop at higher frequencies.
Will the circuit oscillate with Q that low?

Roy Lewallen, W7EL

Referring to http://www.aade.com/lcm2binst/HP.html the measurement freq.
was about 750KHz for the type 61 and 43 materials and about 70KHz for
the 75 material based on the inductances that were displayed.

73, Larry W0QE

Larry Benko wrote:
Roy Lewallen wrote:


Yep, that's perfectly adequate to distinguish the types. You must have
made the measurements at a pretty low frequency. Type 75 has a Q of 1
at about a MHz, and 43 at a few MHz, and they drop at higher
frequencies. Will the circuit oscillate with Q that low?

Roy Lewallen, W7EL


Referring to http://www.aade.com/lcm2binst/HP.html the measurement freq.
was about 750KHz for the type 61 and 43 materials and about 70KHz for
the 75 material based on the inductances that were displayed.

73, Larry W0QE

Darn typo. That should be 750KHz for the type 61 and 43 and 700KHz for
the type 75. Sorry.

73,Larry W0QE

Roy Lewallen wrote:

The 259B is, I maintain, a very good instrument for identifying core
materials and for use in the design of inductors, transformers, and
other magnetic components. I've used mine many times for the purpose
and gotten the results I expected. That was, I thought, the subject of
this thread, but it appears to have drifted elsewhere.


It has certainly drifted away from Australia, and towards the USA.

In the USA, it's a good bet that an unknown ferrite core will be made by
Fair-Rite, and probably one of the more common materials; or else it's
probably a dust-iron core from Micrometals. With help from the catalogs,
and a few known cores for reference, even quite limited test equipment
will have a good chance of identifying the specific product.

But that may not be true in the rest of the world. You may have a core
that is marketed in your home country but imported from another, but
having been manufactured in a third country using a process licensed
from... well, who knows any more? There are no world-standard sizes, and
no direct equivalents between magnetic materials from different
manufacturers. The best you can hope for is to identify the material as
being "somewhat like" a known Fair-Rite mix.

With such uncertainties about the material itself, you can afford far
fewer uncertainties about the measurement. If you don't have advanced
test equipment (or an advanced understanding of the limitations of
simpler equipment) then it may be better to forget about characterizing
the magnetic material. If you want to know if it will work in an HF
balun, it may be much easier to *make* a balun.

On the other hand, if you really want to chase down the problem of
identifying and characterizing unknown cores from anywhere around the
world, the following links may help.

http://users.catchnet.com.au/~rjandusimports/
No coincidence that this site is .au - they know about this problem in
Australia.

There are very useful international cross-reference pages at:
http://users.catchnet.com.au/~rjandu.../xref_mat.html
http://users.catchnet.com.au/~rjandu...ze_toroid.html
Do remember that these are not exact equivalents, only the closest
available. Also note the huge gaps in the tables, where nothing even
comes close.

Another very useful resource is DL5SWB's Mini Ring Core Calculator:
http://www.dl5swb.de/html/mini_ring_core_calculator.htm
This software contains extensive libraries of cores from international
manufacturers, including dimensions and paint colours as well as
magnetic properties. If you know the identity of the core, it will
calculate the inductance from the number of turns. If you have an
unknown core, and can make some meaningful measurements, there are
separate functions to help identify it.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Jun 3, 2:13 pm, "Tom Donaly" wrote:
Whaddaya mean, "believe in"? If I pray to the waves, will they
bring good luck?

Many of the posters here believe that reflected EM waves don't
actually exist
in reality. Their belief systems are interferring with their
understanding of physics.
And yes, it might as well be a religion to which one prays. I know a
number of posters
who pray that reflected waves don't exist because their entire house-
of-cards will
come tumblinging down if reflected EM waves actually exist in reality
- while obeying
all the boundary conditions that Mother Nature dictates for EM waves.
Hopefully,
you are not one of those individuals.
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
On Jun 3, 2:13 pm, "Tom Donaly" wrote:
Whaddaya mean, "believe in"? If I pray to the waves, will they
bring good luck?

Many of the posters here believe that reflected EM waves don't
actually exist
in reality. Their belief systems are interferring with their
understanding of physics.
And yes, it might as well be a religion to which one prays. I know a
number of posters
who pray that reflected waves don't exist because their entire house-
of-cards will
come tumblinging down if reflected EM waves actually exist in reality
- while obeying
all the boundary conditions that Mother Nature dictates for EM waves.
Hopefully,
you are not one of those individuals.
--
73, Cecil, w5dxp.com


Maybe you'll tell me who you think thinks waves of any sort can't
be reflected. I haven't run into anyone who thinks EM waves can't be
reflected, refracted, etc. Maybe there's a misunderstanding somewhere.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:

...
Maybe you'll tell me who you think thinks waves of any sort can't
be reflected. I haven't run into anyone who thinks EM waves can't be
reflected, refracted, etc. Maybe there's a misunderstanding somewhere.
73,
Tom Donaly, KA6RUH

Very good, and oh so relevant!

Krist, even the force on a tennis ball is "reflected" back off a wall!

Better question would be, "What can't be reflected?" (well, ok, high
radiation is NOT easy to reflect!)

JS

On Jun 4, 5:39 pm, "Tom Donaly" wrote:
Maybe you'll tell me who you think thinks waves of any sort can't
be reflected. I haven't run into anyone who thinks EM waves can't be
reflected, refracted, etc. Maybe there's a misunderstanding somewhere.

I don't want to get personal but if you have followed the reflected
wave arguments, you know who they are. Some simple true/false
questions will highlight the argument.

1. Do reflected EM waves actually exist in reality?
2. Is the reflected EM wave a traveling wave?
3. Does a reflected EM wave obey the rules for traveling waves?
4. Do reflected EM waves contain ExB joules/second?
5. Do reflected EM waves have any effect on forward waves in a
constant Z0 environment?
6. Do standing EM waves superceed and obsolete the component traveling
waves?
7. Does reflected EM energy violate the laws of physics by standing
still within the standing wave?
8. Does reflected EM energy violate the laws of physics by just
"sloshing" around?
9. Does reflected EM energy travel in the reverse direction at VF(c)
until it encounters an impedance discontinuity?
10. Is it valid to consider the forward EM traveling wave and the
reflected EM traveling wave separately and then superpose the
resulting fields (voltages, currents)?
11. Are the decades-old EM wave intensity equations from the field of
optics valid for an RF EM wave analysis?
12. Can standing wave current be used to determine the delay through a
75m mobile loading coil?
13. Is the current "drop" through that loading coil just an illusion
caused by superposition of forward and reflected currents?
14. Would the delay be different if only a forward traveling wave was
used for measurement purposes?
--
73, Cecil, w5dxp.com

Cecil Moore wrote:

On Jun 4, 5:39 pm, "Tom Donaly" wrote:

Maybe you'll tell me who you think thinks waves of any sort can't
be reflected. I haven't run into anyone who thinks EM waves can't be
reflected, refracted, etc. Maybe there's a misunderstanding somewhere.


I don't want to get personal but if you have followed the reflected
wave arguments, you know who they are. Some simple true/false
questions will highlight the argument.

1. Do reflected EM waves actually exist in reality?
2. Is the reflected EM wave a traveling wave?
3. Does a reflected EM wave obey the rules for traveling waves?
4. Do reflected EM waves contain ExB joules/second?
5. Do reflected EM waves have any effect on forward waves in a
constant Z0 environment?
6. Do standing EM waves superceed and obsolete the component traveling
waves?
7. Does reflected EM energy violate the laws of physics by standing
still within the standing wave?
8. Does reflected EM energy violate the laws of physics by just
"sloshing" around?
9. Does reflected EM energy travel in the reverse direction at VF(c)
until it encounters an impedance discontinuity?
10. Is it valid to consider the forward EM traveling wave and the
reflected EM traveling wave separately and then superpose the
resulting fields (voltages, currents)?
11. Are the decades-old EM wave intensity equations from the field of
optics valid for an RF EM wave analysis?
12. Can standing wave current be used to determine the delay through a
75m mobile loading coil?
13. Is the current "drop" through that loading coil just an illusion
caused by superposition of forward and reflected currents?
14. Would the delay be different if only a forward traveling wave was
used for measurement purposes?

It's ridiculous to assert that someone "thinks EM waves can't be
reflected" based on the fact that they might happen to take issue with
one or more of your speculations on the laundry list shown above.

ac6xg