Hi Roger,
Attached is a photo of my tweezers and calibration reference box which is similar to a photo within the article.
Yes I have found the tweezers to be surprisingly precise if used in conjunction with a reference PCB which is simply a board that provides good SMD calibration references. After proving the concept I designed a PCB for a calibration reference box. It has a PCB populated with a range of close tolerance L/C/R components physically isolated from the ground plane to minimize effects from stray capacitance. It also provides 0805 SMD Open/Short/Load calibration references. The 0805 SMD cal references provide consistent tweezer tip spacing during calibration. The multi decade value range reference components provide a confidence building tutor platform and are nice to have available for a quick check just to make certain the calibration is good.
The bare tweezers are only a few dollars via AliExpress. The tip contacts, cable and miscellaneous parts add to the cost but I think a pair of tweezers can be built for about $20. Because of procurement efficiencies a second set of tweezers only cost only a few dollars more for the parts. The addition of a proper calibration PCB mounted within a Hammond diecast enclosure more than doubles the total cost. But for those that wish to minimize the cost and just wish to make HF measurements a simple calibration PCB can be made using some prototype board stock (which is what I started with).
The QEX article provides detailed information on how to build and use the the tweezers. There was much trial and error involved initially. Closeup photos and ordering links are provided there. I think anyone interested in building a set of these tweezers should review the article first as I think it would save most builders much trial and error effort. One source for the article is the "ARRL Periodicals DVD 2021" DVD that can be purchased and downloaded from the ARRL site:
As the author of the published article I cannot repeat the details here but I would be happy to try and answer any questions about the information presented there.
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Best Regards,
Tom, VA7TA
