[Elecraft] Balanced tuners

[David Honey]

Strictly speaking, the term "balanced tuner" should not be used for ATUs 
that have the balun on their output. They are inherently unbalanced. With 
highly reactive or mismatched loads, the balun could give rise to 
significant losses.

A true balanced tuner has the balun at the input where, once the ATU is 
propery adjusted, will always be at 1:1 and hence no reactive elements. 
Everything else after the balun is floating wrt RF earth. I think a recent 
survey showed that these tuners typically had losses of 1% or less, and 
rarely more than 3% on topband.

I have the Palstar BT1500A and have been very pleased with it. It's rated 
at 3kw, so with 400W UK legal limit, it's never stressed. Not a cheap ATU. 
Inside, good engineering with very heavy duty relays, silver plated twin 
roller coaster inductors. I have no regrets about trading in my AT1500CV 
(unbalanced) one for the BT1500A. I use it with a 140ft doublet at 50ft, 
and a vertical dipole fed with open wire feeder. One project I was thinking 
of was to make a switching box for several balanced antennas for it that 
also allowed the doublet feeds to be strapped together to make a top-loaded 
vertical being driven against my ground radial system for topband.

It's a pity that no one that I know of does an auto balanced ATU, even for 
100W. Now, if Elecraft did a kit for a 1kw balanced auto ATU, I'd be 
seriously interested. :-) Especially if it had switching for several antennas.

David, M0DHO