I am building replica's of the 70's era C.B. type "snoop loops" which are also known as DF or RF directional finders.... Problem: I cannot locate the "vintage" or so they are called today, electrical components... They are: "Impedance Matching Capacitors", or also known as:"Tuning capacitors" They "were" generally speaking, a small flat square or rectangular block, made of white ceramic material, that had a flat head screw, on top for adjustment. They were about 1 inch or a bit smaller in size. Some also called these tunable resistors, but I cannot find any reference to that name today! The only requirement is that they be of 50 ohm (resistance?) That's where I get lost! The rest was easy, after numerous hours of research and reading articles on google. Here's the basics, IF anyone should want to try to build any of these: A DF loop is a fairly simple and basic device. A piece of 3/8" aluminum/copper tubing, bent into an approximately 10-12" loop, with an impedance matching capacitor mounted at the top, and a shunt fed coax connection near the bottom of the loop. This assembly is then connected to a mast which can be rotated 360 degrees. (12-16" x 3/4" wooden dowel handle) Determining direction was accomplished by turning the loop until the lowest signal (called a null) is obtained, which occurs when the loop is broadside to the direction of the signal. Using an aluminum fish net: about 10-12 inches in outside diameter.... cut a section out of the "top" of the loop to mount the tuning capacitor. attach the coaxial shunt feed, using a hose clamp for the center contact of the coax cable, to one of the side rails. Using a low power walkie-talkie, tune the feed point and tuning capacitor for best VSWR. I don't know if these can still be made, but there is a lot of info on the types for VHF, and 2 meter "Fox and Hound" games.....Even a diagram for building one into an aircraft!