Don't think it is really necessary to use (ferrite) toroids for a
compact 100W capable HF antenna matching unit.
Depending on type of antenna a simple variable capacitor(s) /variable
roller inductor unit will highly likely do the trick, even if remotely
operated.
If the unit needs to have a balun ,you obviously want to use a balanced
feeder, but it is doubtful that an exposed balanced feeder in a 'salt
spraying environment' will be effective.

Frank GM0CSZ / KN6WH

================
Sorry, I should have been more precise. What I wrote referred to
an antenna tuner that covers the various ham/marine bands in the
1.5 MHz to 50 MHz range, i.e inductors and capacitors that are
suitable for use in this 'broad' frequency range. Also, the antenna
tuner probably will have a balun in it, which would not be tuned
and hence would be broadband.

I am trying to set up a rig on a boat, and one of the options is to
make a remote controlled antenna tuner for RX, and up to ~100W TX,
instead of using one of the rather expensive commercial units. The
antenna/tuner will be used to receive marine weather transmissions,
and for CW QSOs on the ham bands.

Thanks,

John, HA5PG/MM