[Antennas] re: antenna tuners

Wed Nov 30 23:07:04 EST 2005

> One less degree of freedom, meaning that the tuning range is less for the
> two knob differential cap design vs. the three knob separate cap design. 
> Of
> course this depends on component values and circuit topology.

I'm sorry - no offense, but I cannot agree with that for two reasons.
1) I have several tuners of both types and have never had any more or less 
difficulty tuning a given antenna with one type over the other type.
2) In EVERY instance of finding the proper tuning point on a C-L-C tuner, I 
have found that one of the two capacitors is at full mesh.
That means it could have been replaced by a fixed capacitor - so long as 
there was also a way to switch the configuration around, depending on the 
load.
So, in spite of the fact that I cannot PROVE it, I believe that the design 
with only one capacitor is as capable as the other.
And, I think my observation of the behavior of the C-L-C tuners is 
sufficient to establish that there was an un-needed extra degree of freedom 
in the design. In other words, the someone got clever with the simpler (?) 
design.
>> What is the difference between a regular antenna tuner
>> that has two capacitor tuning knobs and a roller
>> inductor, and one that has a differential capacitor
>> tuning knob and roller inductor?
>> I know the antenna tuner with the two capacitor tuning
>> knobs can tune just about any antenna or wire. But
>> I'm not sure about the differential capacitor antenna
>> tuners. Can it tune anything as well?

73 de W9DMK - Bob Lay, Dahlgren, VA
http://www.qsl.net/w9dmk
w9dmk at crosslink.net