The "Sharpie" Probe


I wanted to attempt development of a test procedure for alignment of a Bitx20 ssb transceiver using the most basic tools. I already had video's Videos of the process using an oscilloscope, signal generator and a spectrum analyzer. What was needed was a procedure using a RF Probe. I didn't have one so after a search of the internet, I found N5ESE's RF Probe His site has a very good explanation of how a RF probe works. This looked like just what I needed. After a search for a easily obtainable probe housing, I selected this.

The lowly "Sharpie" It can be found almost anywhere and many of us have old, dried up ones laying around. The first step was to remove the felt tip. This is easily done using a pair of needlenose pliers and giving it a pull. Then using an exacto knife, cut off the other end and remove the taperaed part.

Using the needle nose pliers remove the ink reservoir.

You now have a "custom" probe housing.

Next search through the junk box for all of the parts. I used a .02ufd cap because it was the perfect physical size, a 4.7 meg resistor, and a 1N34A diode. I had a nice, flexible, piece of test equipment wire for the ground. I found a copper nail that would be easy to solder to for a tip.

I soldered it all together as per the schematic being careful that nothing could short together when pushed into the probe housing. Using a little shrink tubing can help insure that it will work when assembled.

Next, carefully insert the soldered circuit into the housing, use a little hot melt glue to make the tip rigid and also in the back to strain releif the cables, add a alligator clip for the ground and banana jacks for the meter connection, test, and use.

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