Both of these designs are of the Balanced L or Double L variety. Both
require a balun at the input to convert the 50 ohm unbalanced output
of the transmitter to the balanced tuner & feedline. You still haven't
gotten away from the main cause of inefficiency & power loss which is
the balun. [see http://www.somis.org/bbat.f1.jpg]

These double L tuners can be a PITA to build & use also. You need two
identical inductances at all times in the circuit. This requires
either some mechanical means of driving two identical roller inductors
simultaneously (so that the inductance in each leg always matches) or
two identical switched inductors with exactly the same tap points.

The link coupled design of the Matchbox takes the balun (and it's
potential for power loss) out of the circuit. They are also much
simpler designs, easier to homebrew & tune.

Terry
W8EJO





On Aug 1, 12:19 am, Alan WA4SCA wrote:
If it hasn't been mentioned, the SAMS may probably be the ultimate
unit: http://www.eham.net/reviews/detail/6677 However, its cost is
probably equal to what many have invested in their entire shack. Still
not cheap, but more reasonable, is the AT-515:http://www.hamware.de/hardware/tuner515/at515-e.htm Both were
represented at Dayton this year, and are clearly not Might Fine Junk.

--
Alan
WA4SCA