I haven't got an antenna analyser to do the above checks. The toroids
came in a box of stuff from a hamfest. They are in a packet which has
the brand name "Duratech" printed on it.

wrote:
I haven't got an antenna analyser to do the above checks. The toroids
came in a box of stuff from a hamfest. They are in a packet which has
the brand name "Duratech" printed on it.


If you have any means at all of mesuring
inductance, you can go he

http://en.wikipedia.org/wiki/Inductor
Inductor - Wikipedia, the free encyclopedia

Find the formula (#6) for the inductance
of a toroidal ring. Enter the
appropriate values and solve for u
(permeability of the core). Then look at
ferrites and iron power core properties
with the calculated permeability at the
test frequency. You'll probably find
several core materials that fit.

I think that's about all that can be done.

Chuck

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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

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

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

1) Is your junk drawer supply good?

2) Got a freq counter?

If you answered yes to the above, build a simple 1 transistor
oscillator. Wrap a few turns on the toroid, and shunt it with a know
capacitance. Read the freq of the oscillator, using a chart available
on the web, note the capacitive reactance of the cap value in ohms.

Since capacitive reactance = inductive reactance in ohms at resonance,
it is now a simple matter to translate in the inductive reactance of the
torrid coil into uh/mh--using the osc freq and a chart from the web ...

Warmest regards,
JS


Since

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

On Sun, 03 Jun 2007 12:13:50 -0700, wrote:

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?

Hi Herbert,

Pass a wrap of wire around the material if it is a bar, or through it
if it is a toroid. Connect this to the output of the SWR meter. Hit
it with a short blip of power and note the SWR. You have the
multiple/divisor of 50 Ohms. Give it two wraps, or two passes and
repeat for more clues. Repeat at the frequencies of interest. Make a
chart.

Try to keep the power low and application short so you don't burn your
fingers.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

Hi Herbert,

Pass a wrap of wire around the material if it is a bar, or through it
if it is a toroid. Connect this to the output of the SWR meter. Hit
it with a short blip of power and note the SWR. You have the
multiple/divisor of 50 Ohms. . .

Sorry, that's simply not true. You're almost certain to have reactance
-- possibly, a lot of it -- in which case the SWR can be vastly
different than the impedance divided by 50 ohms or its inverse.

Roy Lewallen, W7EL

On Sun, 03 Jun 2007 18:48:00 -0700, Roy Lewallen
wrote:

Richard Clark wrote:

Hi Herbert,

Pass a wrap of wire around the material if it is a bar, or through it
if it is a toroid. Connect this to the output of the SWR meter. Hit
it with a short blip of power and note the SWR. You have the
multiple/divisor of 50 Ohms. . .

Sorry, that's simply not true. You're almost certain to have reactance
-- possibly, a lot of it -- in which case the SWR can be vastly
different than the impedance divided by 50 ohms or its inverse.

Simplicity is not to be dismissed that easily (no one needs to spend
$500 to figure out ferrite). A moment's worth of very little power
will suitably allow for heat to discriminate reactance from
resistance.

73's
Richard Clark, KB7QHC