The MFJ-974B is a fully balanced true balanced line antenna tuner. It gives you superb current balance throughout its very wide matching and frequency range. The MFJ-974B is a fully balanced wide range T-Network using four gear driven 1000-Volt air variable capacitors and high-Q air wound tapped inductor for 80-10 Metres and separate inductor for 6 Metres.
The tuning components are mounted symmetrically to insure electrical balance.

A 1:1 current balun is placed on the low impedance 50 input side to convert the balanced T-Network to unbalanced operation.
The balun is made of 50 ferrite beads on RG-303 Teflon? coax to give exceptional and efficient isolation.
It stays cool even at maximum power.