Why wooden box is improper for LRL

[WM6]

Dowsers have a lot of trouble using LRL devices built in wooden boxes. Why?

Seems no one is, meet of those different difficulties, thinking of wooden boxes as possible sources of those problems.

Wooden boxes are great material for electronic boxes (like radios etc.) used inside in houses in relatively stable climate conditions.

But if you use high sensitive electronic incorporated in wooden boxes outside in very different climate conditions (temperature, relative humidity, mechanical stress, signal damping etc.) it is about quite another matter. Even more, those LRL electronic circuits not are only incorporated in electronic boxes, but are with very sensitive parts of circuits, as antennas, tank circuits etc., not so seldom in direct galvanic touch with wooden boxes. Yes, in direct galvanic touch with wood.

Considering only the hygroscopic properties of wood, which, taking it into changing climatic conditions, changing its conductivity, then we should not be surprised by the great whim in the operation of these creations.

I do not claim that those LRL results, using other materials, were much better than the current, which are null and void. But certainly these devices in a housing made ​​of other materials, would act more stable and would not be so strange subject of sensitivity to different climatic conditions, such as in present wooden boxes.

Using wooden boxes for such outside devices are from electronic point of view in most cases a big mistake in design.

If you wish your LRL to work stable, one important thing is to avoid wooden design especially if your sensitive circuit is coming in direct galvanic touch with LRL housing or its wooden parts.


PS: I am easily go fatigued with English, so I hope that our excellent and very discernibile science-interpreter J_P will add some more in this matter.

[Geo]

Hi WM6.
Wooden boxes are better because are not sensitive to static.
But as you wrote are sensitive to moisture.
An Investment with varnish is a good solution.

[WM6]

Originally Posted by Geo

Hi WM6.
Wooden boxes are better because are not sensitive to static.
But as you wrote are sensitive to moisture.
An Investment with varnish is a good solution.

Geo, good varnish is not wooden, varnish is synthetic substance, so if you paint your wooden box with varnish, it is no more wooden box regarding static electricity, but synthetic box, cause of its synthetic surface. It has static properties of varnish no of wood.

Another problem is that there is no varnish that can protect wooden box 100% from atmospheric impacts and relative humidity in air outside, so your synthetic painted wooden box is even worst than if you use pure antistatic-synthetic made box.

[Geo]

Originally Posted by WM6

Geo, good varnish is not wooden, varnish is synthetic substance, so if you paint your wooden box with varnish, it is no more wooden box regarding static electricity, but synthetic box, cause of its synthetic surface.

Another problem is that there is no varnish that can protect wooden box 100% from atmospheric impacts and relative humidity in air, so your synthetic painted wooden box is even worst than if you use pure synthetic wooden box.

I have tried it with good results, especially at coil housings. I have not eratic signals..

[WM6]

Originally Posted by Geo

I have tried it with good results, especially at coil housings. I have not eratic signals..

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?

[J_Player]

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?

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