Quote:
Originally Posted by WM6
Sure if you paint with varnish, there is no more wood in contact with circuit.
Which devices are you speaking about? Static LRL or geomagnetic LRL sensor?
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The varnish and other paints that I see coated on wood LRL boxes is sometimes several coatings.
And many wood LRL boxes also have paint or varnish on the inside. But it is true, water vapor is a gas which can penetrate through small pores in the paint to enter the wood fibers and increase the humidity.
The increase in humidity will cause most wood fibers to expand a small amount to make small changes in the box dimensions, and can even cause the box to warp to slightly non-rectangular.
This happens when one side of the box is warm from the sun to drive away the humidity, and the other side is cooler to conserve the humidity in the fibers.
I would expect the only serious problem is when high impedance parts of a circuit are in contact with the wood or other partially conductive parts of the box.
Maybe this is part of the reason why we see several people who build the same project find different performance.
For the parts of a circuit which are lower impedance, I do not think there will be so much problem with circuit malfunctions due to leakage paths.
But there are definitely consequences for absorbing electromagnetic waves that could be significant at some frequencies and power levels.
It seems that it would depend on what kind of energy the transmitter is expected to pass through the box, and what kind of energy a receiver is expected to receive through the walls of the box.
I would think that it is important to consider what kind of signals you are sending and receiving in order to choose a good box material.
In some applications, maybe a metal box is best, but others may be better with plastic or wood fiber based enclosures.
A varnished cardboard box could even work if the material is strong enough.
Maybe a teflon box will have some use for special applications because it has good insulating properties, and does not pass moisture.
Best wishes,
J_P