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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