Hi David,
I know a little about this.
The T-match provided manufactures with a way to get more impedance
matching range out of fewer components in the box. Its basically a
step-up/step-down matching network. Its marketing value is added
versatility....hence the "versa"-tuner became quite popular.
Most auto-tuners are L-networks.
The MJF-balanced tuner actualy puts the caps in series, so its kind of a
double T-network, and very effective for wide-range tuning needs, from
what I hear.
It uses a 15" long coax lenght with beads as a choke to minimize RF from
the coax shield.
The L-network and T-network are both unbalanced configurations.
The Johnson box was a balanced configuration, and was superseded, for
the most part when baluns started to be put into unbalanced tuners to
convert the unbalanced to balanced condition. The J-box was an awesome
balanced tuner, but with a limited matching range. Many hams in the
days of the J-box operated only on one or two bands, which the J-box
easily facilitated.
Duane
N1BBR
Can anyone point to why the single coil Z match wasn't commercialized
rather than the T match? (Perhaps it's a historical thing and
manufacturers just copy each other, notwithstanding the Johnson Matchbox
of course, which is no longer produced.)
David
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