Iron Powder Toroid - weatherproof?
 

Ok, dumb question. Can a Iron Powder Toroid be used outside without
being weatherproofed? Can it be painted with enamel and the used that
way? -Scott, WU2X

Iron Powder Toroid - weatherproof?
 

Iron Powder Toroid - weatherproof?
 

Iron Powder Toroid - weatherproof?
 

Roy Lewallen wrote:


You often use powdered iron when you need high Q in an inductor. Water
between turns can seriously degrade the Q. Painting with enamel might
lower the Q somewhat, but nowhere near as much as water. To maintain the
best Q, you need to keep water well away (say, a couple of times the
turn spacing) from the wires. No physical harm will come to the core
from being outside in the weather.


Here's a link to an old Boonton paper
that describes measurement of inductor Q
at 400 MHz (see page 3) when the
inductor is immersed in tap water. In
Boonton's experiment, no appreciable
effect on Q was noted, except when NaCl
was added to the water. ;-)

Is the greater effect of water on a
powdered iron inductor caused by the
much higher permeability of the iron
than of the air-wound coil Boonton used?

Anyway, it's an interesting paper.


http://www.hparchive.com/Boonton/BRC...otebook-28.pdf
BRC-The-Notebook-28.pdf (application/pdf
Object)

73,

Chuck

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Iron Powder Toroid - weatherproof?
 

Iron Powder Toroid - weatherproof?
 

news.albasani.net wrote:
wrote:
Ok, dumb question. Can a Iron Powder Toroid be used outside without
being weatherproofed? Can it be painted with enamel and the used that
way? -Scott, WU2X


Hmmm, from the others answers, I suspect they all have only dealt with
cores which have come coated with some protective coating (paint,
enamel, etc.)

I took it for granted you were speaking of the ones which can be cheaply
obtained, at times, which have not passed specs but are completely
usable; however, the manufacturer neglected to coat them ... without
coating the core shows oxidation damage with time.

Regards,
JS

Out of curiosity, I immersed a 37 uH
inductor wound on an FT37-43 core in tap
water. Using a (1 kHz) inductance meter,
I saw no change in inductance.
Unfortunately my bench has been co-opted
by other projects and a measurement of Q
at RF is in its own queue.

Also, from the Micrometals website:

"Micrometals recommends that all
uncoated cores should be sheltered from
high humidity or rain since they will
eventually form surface rust."

73,

Chuck

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Iron Powder Toroid - weatherproof?
 

Chuck wrote:

...
Out of curiosity, I immersed a 37 uH inductor wound on an FT37-43 core
in tap water. Using a (1 kHz) inductance meter, I saw no change in
inductance. Unfortunately my bench has been co-opted by other projects
and a measurement of Q at RF is in its own queue.

Also, from the Micrometals website:

"Micrometals recommends that all uncoated cores should be sheltered from
high humidity or rain since they will eventually form surface rust."
...
Chuck
...

Chuck:

Yes, that is what mainly worries me, oxidizing of the iron core (or,
rust.) I am not even sure how the rust would degrade the cores
performance; since, the sheer mental picture of the physical look of a
corroded balun is enough to make me attempt to escape this condition. I
have "revived" old oxidized cores with tripoli and a buffing wheel, then
a protective coating.

I always attempt to waterproof any balun I make. Sometimes this takes
form as an old plastic container with holes in the bottom for any water
which leaks in to escape, but keeps the rain off ...

Regards,
JS

Iron Powder Toroid - weatherproof?
 

Iron Powder Toroid - weatherproof?