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Characterizing my first attempt at copper-only passives

Last year, I kind of got a bee in my bonnet about trying to see if I could accurately (?) make small RF passives out of copper, rather than buying 2pF NP0 capacitors or something, as part of a long-on-the-horizon project to make extremely inexpensive GHz-class oscilloscope probes. I figured that the right place to start was to fab out a board on JLCPCB's JLC04161H-3313 stackup with a handful of calibration standards, and some of the passives that I wanted to measure.

My understanding is that it's good for when you're lazy and want to deembed a known length of ideal transmission line that you have attached to the end of your already-calibrated S11 measurement setup. Previously, we tried using the open / short / load standards on the board to deembed the connector launch and transmission line, but those gave very bizarre results. Interestingly, the dip effect of the extension is even greater in this test, while the rise from the calibrated-to-board-standards version is about constant in terms of total capacitance.

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