Palstar MW550P is a very good medium wave antenna tuner (500 KHz to 2800 KHz), especially for long lengths of wire, and a preamplifier as well, which covers the range from 150 Khz to 30 Mhz. Using this device you can avoid side band interference in MW, as the variable capacitor tunes the desired signal sharply. The main tuning knob has got a slow motion mechanism, so that accuracy is ensured. The tuning process gives a particularly good feeling to the operator.
Some photos of the interior. One can see a well constructed unit.
The variable capacitor.
The balun (9:1 ?).
It can be used as short wave preamplifier with any length of wire, even a short one. To tune this kind of antenna another passive tuner, such as Mizuho AT-2000 may needed.