On Sat, 02 Jun 2007 09:46:31 -0500, Cecil Moore
wrote:

wrote:
All I
want to know is if the toroids would be any good for HF 1:1 baluns.

An antenna analyzer, like the MFJ-259B, is a very
useful piece of test equipment for all types of
measurements of this kind. Using the MFJ-259B, I
discovered that the Amidon brochure, "showing typical
'Z' in ohms for one turn at 25 MHz", is misleading.
Their "one turn" goes through the core twice which
I consider as being two turns. That's bad news for
w2du baluns.

If you could gain access to an MFJ-259B, you could
run the same kind of measurement on your toroids.
Heck, if you send one to me, I will run the experiment
and send it back to you.

Hi Cecil,

You need to move up a notch. Check out http://w5big.com/

I've had one for several months now and won't want to be without it.

Danny, K6MHE

Danny Richardson wrote:
You need to move up a notch. Check out http://w5big.com/
I've had one for several months now and won't want to be without it.

Thanks for the URL, Danny - didn't know about it.
--
73, Cecil http://www.w5dxp.com

wrote in news:1180792808.218763.251660
@n15g2000prd.googlegroups.com:

Hello Owen,
I have tracked the product down to Jaycar but they don't know anything
about the material. The person I contacted was very vague and couldn't
steer me towards anybody that would know what material it was. All I
want to know is if the toroids would be any good for HF 1:1 baluns. I

You didn't ask that question initially.

As I said, I think that the material is low loss below about 1MHz. I am
away from home at the moment and don't have access to my records of
testing the things.

I doubt that the material is suitable for a HF voltage balun. Lossy
ferrite is still usefull for suppression purposes, and you could probably
use the cores for a 1:1 choke style balun at HF. One of the issues with
lossy choke baluns is efficiency of the solution, and more importantly
power rating.

Jaycar also sell powdered iron cores in similar sizes (LO1246, HY-2
material, ui 75, Al 165nH). They have much lower ui (need more turns for
a given inductance), lower loss, and are more expensive.

have just made a balun using a FT-140-61 which is very close to the
same dimensions as the 2 toroids in the Duratech packet. If they can
be used they are a fair bit cheaper than sourcing FT-140-61 toroids.

For some reason, US magnetics are overpriced in Oz. It seems everyone
charges FedEx rates to post a couple of dollars worth of cores that
should fit in a padded bag for $5. There is a market there for someone in
the US to sell reasonably priced Fair-rite or similar cores on Ebay with
low postage.

The other option is to try Neosid in Sydney, have a look at their web
site. I know they do a range of ferrites and powdered iron cores of
various shapes and sizes.

In reply to Richard Clark, yes I do have a SWR meter.

If a given balun causes a poor SWR reading on a known dummy load, then
the balun is inadequate, but the converse does not necessarily apply. The
test is an important one, but not comrehensive.

Owen

Cecil Moore wrote in news:9pf8i.10153$4Y.6557
@newssvr19.news.prodigy.net:

wrote:
All I
want to know is if the toroids would be any good for HF 1:1 baluns.

An antenna analyzer, like the MFJ-259B, is a very
useful piece of test equipment for all types of
measurements of this kind. Using the MFJ-259B, I
....

The '259B is no doubt a handy device, but very limited for measuring
components. Have you tried to measure at an inductance that has more than
250 ohms of reactance at some frequency of interest? Have you tried to
explore self resonance of a coil..., invariably it runs into the same
problem of inductive reactance going off scale way below the point at
which self resonance bites in.

When talking about ferrite or powdered iron cored inductors of reactance
over 200 ohms, where mu is frequency dependent and flux dependent, I find
the '259B nearly useless.

Owen

Owen Duffy wrote:

The '259B is no doubt a handy device, but very limited for measuring
components. Have you tried to measure at an inductance that has more than
250 ohms of reactance at some frequency of interest? Have you tried to
explore self resonance of a coil..., invariably it runs into the same
problem of inductive reactance going off scale way below the point at
which self resonance bites in.

When talking about ferrite or powdered iron cored inductors of reactance
over 200 ohms, where mu is frequency dependent and flux dependent, I find
the '259B nearly useless.


I've had just the opposite experience. I find the 259B to be extremely
useful in determining ferrite types and the impedances of inductors.
Generally a single "turn" (pass through the hole) is adequate for
measurement. For most toroidal inductors the impedance is closely
proportional to the square of the number of turns, so the value of
multi-turn inductors can be extrapolated with reasonable accuracy. Of
course, two or three turns can be used for measurement if the unit can't
resolve the impedance of a single turn.

The frequency dependence of the mu and loss is just why the 259B is so
useful -- I can find the impedance at the frequency or range of
frequencies it'll be used at.

I very seldom design magnetic components for applications where flux
density noticeably alters the impedance. If the signal is so large as to
permit this to happen, you'll be generating serious harmonics and, if
multiple signals are present, intermod. If the saturation is being
caused by DC, it's often possible to bias the core with the same current
while making measurements. And I've never hit a powdered iron core with
enough signal or DC to get anywhere near saturation. They tolerate much
higher flux density than ferrites.

I'd really feel handicapped in designing baluns and wideband
transformers, in particular, without my 259B or something similar.

Roy Lewallen, W7EL

On Jun 2, 5:28 pm, Owen Duffy wrote:
The '259B is no doubt a handy device, but very limited for measuring
components. Have you tried to measure at an inductance that has more than
250 ohms of reactance at some frequency of interest? Have you tried to
explore self resonance of a coil..., invariably it runs into the same
problem of inductive reactance going off scale way below the point at
which self resonance bites in.

Like anything else, there is a limit to the usefulness of an MFJ-259B
but
it is far from useless. Toroids can be characterized by using one or
two
windings to keep the impedance within the 259's range. And self-
resonance
in a coil is super easy. Set the coil up as a base loaded mobile
antenna
without a stinger. Find the first lowest impedance. That's self-
resonance
when the coil is 90 degrees long and the reflected wave is
interferring
with the forward wave at the test point.

Some of the things that limits the usefullness of the MFJ-259B are the
concepts
of the user. If one doesn't believe in (or ignores) the separate
existence of the
forward and reflected waves, then the 259 becomes a lot less useful.
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
On Jun 2, 5:28 pm, Owen Duffy wrote:
The '259B is no doubt a handy device, but very limited for measuring
components. Have you tried to measure at an inductance that has more than
250 ohms of reactance at some frequency of interest? Have you tried to
explore self resonance of a coil..., invariably it runs into the same
problem of inductive reactance going off scale way below the point at
which self resonance bites in.

Like anything else, there is a limit to the usefulness of an MFJ-259B
but
it is far from useless. Toroids can be characterized by using one or
two
windings to keep the impedance within the 259's range. And self-
resonance
in a coil is super easy. Set the coil up as a base loaded mobile
antenna
without a stinger. Find the first lowest impedance. That's self-
resonance
when the coil is 90 degrees long and the reflected wave is
interferring
with the forward wave at the test point.

Some of the things that limits the usefullness of the MFJ-259B are the
concepts
of the user. If one doesn't believe in (or ignores) the separate
existence of the
forward and reflected waves, then the 259 becomes a lot less useful.
--
73, Cecil, w5dxp.com


Whaddaya mean, "believe in"? If I pray to the waves, will they
bring good luck?
73,
Tom Donaly, KA6RUH

i do would that help me with my mess of ferrites?

On Jun 1, 1:08 pm, Richard Clark wrote:
On Fri, 01 Jun 2007 11:03:30 -0700, wrote:
I haven't got an antenna analyser to do the above checks.

Do you have a SWR meter?

73's
Richard Clark, KB7QHC

Tom Donaly wrote:

...
Whaddaya mean, "believe in"? If I pray to the waves, will they
bring good luck?
73,
Tom Donaly, KA6RUH

Who knows? Maybe?

At the present time, it is unknown if RF energy is photons, waves or a
combination of the two. It is known that rf exhibits qualities ...

So yes, a belief akin to what one must hold for his creator is in order
here!

But then, you already knew that ...

JS

Roy Lewallen wrote in
:

Owen Duffy wrote:

The '259B is no doubt a handy device, but very limited for measuring
components. Have you tried to measure at an inductance that has more
than 250 ohms of reactance at some frequency of interest? Have you
tried to explore self resonance of a coil..., invariably it runs into
the same problem of inductive reactance going off scale way below the
point at which self resonance bites in.

When talking about ferrite or powdered iron cored inductors of
reactance over 200 ohms, where mu is frequency dependent and flux
dependent, I find the '259B nearly useless.


I've had just the opposite experience. I find the 259B to be extremely
useful in determining ferrite types and the impedances of inductors.
Generally a single "turn" (pass through the hole) is adequate for
measurement. For most toroidal inductors the impedance is closely
proportional to the square of the number of turns, so the value of
multi-turn inductors can be extrapolated with reasonable accuracy. Of
course, two or three turns can be used for measurement if the unit
can't resolve the impedance of a single turn.

The frequency dependence of the mu and loss is just why the 259B is so
useful -- I can find the impedance at the frequency or range of
frequencies it'll be used at.

Roy, with respect, you are describing work-arounds for the inability of
the '259B to make useful measurements on inductors over about 200 ohms
reactance.

Sure, the instrument can be used to characterise a core, and that
information extrapolated to design an inductor with higher reactance, but
you cannot measure the larger inductance directly, or discover reliably,
the properties of the larger inductor like self resonance effects, or
loss.

I won't address defensive posts by others who seem to have chosen to
ignore my qualification "When talking about ferrite or powdered iron
cored inductors of reactance over 200 ohms".

An example of the traps: a chap recently confirmed to me that indeed mu
is frequency sensitive as demonstrated by the '259B measurement of the
inductance of an inductor over HF which showed inductance was highly
frequency dependent. The problem was that the inductive reactance was
over 250 ohms at most frequencies of measurement, and the '259B
calculates inductance without warning that the value is unreliable
because of the magnitude of reactance on which the inductance is
calculated. Try measuring a 30uH coil's inductance over 2-30MHz using a
'259B and you will see what I mean.

Owen