My antenna is at 10 m and extends 32 m in length. This is rather small for MF however I don’t have more space available.
Nevertheless I was able to build quite a striking antenna system.
To achieve a reasonable RF grounding the backyard area is covered with lots of stainless steel wire. Much of it was put under pavement and is invisible year-round. When the backyard is not used during winter time, more wire and wire mesh is added to further improve grounding.
The tuning variometer provides compensation for the reactive part of the antenna load impedance. Its inner coil may rotate continuously and does not require any limit switch or sliding contacts.
When operating the LF band another coil must be connected in series...
The transformer converts the transmitter output impedance (50 Ω) to the resistive part of the antenna impedance whose reactive part becomes compensated by the variometer. As an alternative not involving a transformer, matching can also be achieved by tapping the grounded coil. However the correct tap usually is not found on a full turn which makes it difficult to localize the correct position and reduces matching accuracy. Moreover it’s a difficult task establishing a tap when hf litz wire is used for the coil.