This is my implementation of the N5ESE Ballpoint RF Probe. It was very easy to build, although I made a number of design changes due to the parts that I had available or was able to obtain. If I recall correctly, I used a 1N260 rather than a 1N34A. I did not create a small circuit board. Instead, I free-formed the circuit and electrically isolated the components using heat shrink tubing. I also used 1/8-inch K&S copper tubing instead of the copper tape in N5ESE's design. The pen barrel that I had just happened to accept the copper tubing perfectly. The probe tip is made from a brass screw that was in the junk box. It was sharpened to a point with a file. I don't know if it makes that much of a difference for measurements, but I used 75-ohm coax to connect the probe to the banana plugs. I guess it really hasn't mattered because I have yet to use this RF probe after building it.