Last summer I built a variometer so I could adjust the match on my top loaded vertical to compensate for changes in operating frequency, ground moisture and etc. I followed the instructions at https://wg2xka.wordpress.com/the-variometer I tried to keep the Q high by leaving a little space between windings. I had to decrease the inner (rotatable) inductor size to keep from having the tuning be too critical. The Q was well over 200

I shortly afterwords added remote tuning capability. I use a small, waterproof servo motor driven by a Raspberry Pi. Abbreviated instructions for installing the code is at https://github.com/kb8u/web-servo

I had been using a 40m dipole with the coax conductors shorted together at the bottom. Since the picture was taken, I replaced the vertical radiating element (coax) with wire to lighten the antenna since it had fallen down in a big wind storm. Also, the wires to the servo proved irresistible to a rabbit (which chewed through them) so I repaired it and covered the wires with a plastic cover.

Initially it worked flawlessly, but now sometimes the servo doesn’t turn at first until I run the control back and forth. I have not yet diagnosed what’s wrong. It is exposed to the weather so covering it would probably help. For now the problem is just an annoyance.