A 1:1 Choke/Line Isolator for use across HF frequencies and handles up to 1kW RF power (assuming 1:1 SWR). Internally, it's the same as our 1:1 Balun but with SO239 connectors at each end. Wound using RG142 coax on an FT240-31 core, this Choke offers resistive performance 3.5MHz up to 30MHz - Much better than an "ugly-balun" made from 20ft of RG58 around a bottle/pipe!
Picture 3 shows the inside of a similar model, the Doublet/G5RV Choke which has the same core/coax, but screw terminals rather than an SO239 connector.
We also have a 100w version in a smaller box, too!
Made (and used) by us - Be weary of any supplier who can't (or won't) tell you what's inside the box you buy!