[Antennas] Johnson Tuners

Mon, 9 Jun 2003 08:34:04 -0400

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=D8OJH

Probably because they are sometimes not as efficient. Link coupling in fin=
al 
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 p=
ut. I never 
could get more than a few watts out of it. I changed the tank to a pi netw=
ork, 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 sa=
y, they 
have to be a weak link in the chain for a matching network too.