Another idea for LRL experimenters to think of is the variations that wood can make for some electrical circuits. When we are working with electrostatics, and with small electromagnetic signals, the conductivity of a wood box can work to cause anomalies in the air, or to block certain electrostatic fields. The same conductivity that we find with wood during high humidity can cause electromagnetic waves to become polarized because the electric component of a wave is shorted in the plane of the wood surface.
This can happen any time the wood has become conductive because of absorbing moisture, or for other reasons such as conductive paint. (Metal flake paint can have some degree of conductivity, and black paint with carbon pigment can be partially conductive).
If an electromagnetic wave becomes polarized, then the reception of this wave will be altered so it is not received in the same way as when the conductive wood is not present.
Of course, a metal box will have the same effect, and maybe stronger. Metal boxes are capable of completely blocking some kinds of signals.
But here is where we can find a problem:
If we have a wood box that can absorb moisture to become more wet or dry depending on the humidity and the temperature, then the conductivity of the wood can change to cause
changes in the circuit performance which vary with the weather. This means the
wood box can be the cause of a circuit to perform well in some weather conditions, then perform bad in other weather conditions.
If the conductivity of the wood is causing variations in the circuit performance, this could deceive the LRL user to believe that the weather is acting on the soil, or on the atmospheric electric charges, when the poor performance is really caused by the wood box. One way to test to see if the wood box is a problem is to change from wood to plastic during weather when the performance is bad. Then see if there is any improvement in performance. If we see bad performance in wood, then improvement in plastic, we know the box is part of the problem. Then when the weather is very warm and dry, we can change back to wood to see if the performance changes. If the performance does not change when you are using wood in warm, dry weather, then it will confirm the wood was causing a problem only when the weather was damp. In warm dry weather, the wood should work similar to plastic, But wood should perform more like a metal box when the humidity is high. For electrostatic circuits, a wood box may be a good thing because it will not easily collect a static charge. But be careful to keep the antenna circuits separated so they do not touch the wood.
We should remember that any RF that is broadcast from the box will be following near-field broadcast dynamics which are noticeably different than RF which has traveled many Km distance from a transmitter. You can expect a 90 degree phase angle in the RF that you send out, and if the supports for the broadcasting coil or the box behind it is partially conductive, then you can expect some of the wave to become polarized. We also expect the wave to become polarized vertically in the region where the wave penetrates the ground, if the ground is conductive.
Take a close look at some of the commercial LRLs. The materials near the broadcasting and receiving coils are intentionally made to be iron or hard-pressed wood fiber or circuit board materials. This was done for a reason.
When we see many different construction methods for experimental LRLs, I am not surprised to see people reporting different performance from the same circuit designs. The circuit design is only one part of the locator. The Tx and Rx antennas are another part which will perform much differently if they are not built and arranged the same.
Best wishes,
J_P