RF Choke with Bifilar Windings – Done!

Here is an RF Choke built using 11 bifilar turns of #14 house wire on a Fair-rite FT240-31 toroid. The choke is mounted in a 3D printed case I pulled off of Thingiverse. K9YC does not recommend mounting an RF choke in an enclosure due to thermal effects but I’ll be running at a max of 100W so I am not expecting this problem.

Here are the measurements made with the miniVNA Pro as described previously. First the choking resistance:

Resistance is greater than Reactance on 80m thru 12m with a choking resistance above 3k Ohms. Here is the Transmission loss which is very close to K9YC’s measurements of similar chokes:

Finally here are the reflection measurements with a 50 Ohm load:

SWR rises to close to 2.5:1 by the time the frequency reaches 30Mhz. This is the only measurment I am a bit concerned with as I want a choke I can place at the rig input. I’ll use two series chokes in this location using 50 Ohm RG400 for the windings. I can use this choke at antenna feedpoints for portable use and any mismatch can be dealt with by the antenna tuner. Cable arrives tomorrow so I should have some comparison data soon.