Plate capacitor.

I've recently taken up a renewed effort to understand the role of ground in antenna systems, thanks in part to having more time during the lockdown, and also the remarkable results from the coast.

I built a plate capacitor for measuring different soils a couple of years ago, but I never quite finished it.  It was based on the simple design published in the ARRL Antenna Handbook.

So, I fixed the aluminium plates to the frame properly this morning, and provided proper connection points for the capacitance and shunt resistance measurements.

The box has a sliding trap door, which allows the soil to be easily jettisoned once the measurements are complete.  It's important to varnish the inside of the box if you make it out of wood, to minimise moisture getting into the wood and forming a bridge between the plates.  Plastic is probably a better choice if you have any.

Anyhow, here's what I came up with: