[Amps] Russian power L-coupler

[Tom W8JI]

> Has anyone tried to use these couplers in a tank circuit? 
> Both coils
> could be tuned by variable capacitors and the coupling 
> between the two
> coils would then be optimized for maximum power output.

They are sometimes called variometers.

They have terrible Q at minimum inductance, especially at 
higher frequencies. Of all the common methods, this is the 
least efficient way to vary inductance over a wide range.

I'd stay away from them unless there is no other option, or 
unless the desired inductance adjustment range is very 
small!

73 Tom