[RFI] Several USB cables - single toroid

[Jim Brown]

On 2/21/2024 8:54 PM, K9MA wrote:
> Polarity is just a simple case of 180 degrees out of phase.

Only at a single frequency.

But Phase has meaning only at a single frequency. A network will have a 
different phase shift for every frequency.

A length of transmission line will be 180 degrees at only one frequency.

If I want to drive two antennas 180 degrees out of phase for their 
entire bandwidth, the only way to do that is to reverse the polarity of 
one of them. If I add a half-wavelength to one at the center of their 
operating range, they will be 180 degrees out of phase at that 
frequency, but +/- some number of degrees as I move away from that 
frequency. If they are relatively broadband antennas, that can change 
their pattern enough to matter!

73, Jim K9YC