[Antennas] Johnson Tuners

Mon, 9 Jun 2003 15:28:46 -0700 (PDT)

   One variation in the tuner design is to use the balun on the input to the tuner, and then use a conventional unbalanced tuner modified to have floating inputs, and outputs. The balun sees no reactance when the tuner is matching the load, and this works well 160 -80 - 40 meters. Above that the circuit is not well balanced. I have used this arrangement for a long time with excellent results.

Jim Candela
WD5JKO

Brian Carling <[email protected]> wrote:On 9 Jun 2003 at 0:25, Les Severson wrote:

> With all the renewed interest in balanced fed all band dipoles I am
> wondering why some manufacturer hasn't resurrected the link coupled,
> Johnson design for a tuner. It sure beats cranking a rotary inductor
> and a 4:1 balun for feeding a balanced line. Just look at what Johnson
> tuners are going for on Ebay.. hi
>
> 73 to all, Les, W�OJH

Probably because they are sometimes not as efficient. Link coupling in final
amplifiers can tend to be inefficient unless you get all the values right on each
band. I had an Eldico transmitter with an 807 final and link-coupled out put. I never
could get more than a few watts out of it. I changed the tank to a pi network, and
immediately the output soared to over 30 watts.

I can't say what those 4:1 baluns will do to the efficiency, but as you say, they
have to be a weak link in the chain for a matching network too.

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