Topband: Mother of all ferrite common-mode coaxial chokes

[Paul Christensen]

> It seems Frank, Jim, myself, and many others are in exact agreement. This 
> is
> because underlying science is universally logical and valid, and proven 
> both
> by measurements and by time in thousands of commercial systems.

What I think is missing from the discussion is that any benefit from using a 
CM choke between shack hardware can be undermined by necessary parallel 
paths.  Consider a CM choke placed on the RF cable between a transmitter and 
amplifier.  Not only is the shield of the coaxial cable connected between 
the equipment, but so is the AC ground conductor, and shielding of the PTT 
key line and ALC line (if used).

But, the CM choke may still offer some benefit.  I use a choke between my 
USB keyer and PC.  The USB line sprays RFI/EMI without the choke.  Yes, I 
could open up the equipment and look for Pin 1 problems.  But I don't want 
to.  If it's inside the PC, I want to leave it alone.  Same for the keyer. 
It's probably the lazy way out, but with some equipment, I just don't want 
to make internal modifications.  In those instances, I'm not opposed to 
trying a CM choke between shack hardware.  If it works, great.  If not, then 
I have the choice of living with the problem, making invasive modifications, 
or investigate some alternate cabling method.

Paul, W9AC