Effect of Common Mode Chokes

22 Feb 2022

No Common-mode Choke

KiwiSDR waterfall with no common-mode choke

Common-mode Choke

KiwiSDR waterfall with common-mode choke

Common wisdom is that common-mode chokes on antenna coax cables are an effective way to prevent common-mode noise from inside the shack from propagating on the coax shield and coupling to the active element(s) of the antenna the coax cable is connected to.

In the KiwiSDR waterfall views above, it should be possible to view this effect. In particular, the 2-4 MHz area is much worse without the common-mode choke.