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Good luck with the waveguide! Have you done anything that high-speed with OSH Park before? I'm waiting on a PCIe board from them that I hope will do Gen3 speeds (8GHz) over 2.5-inch traces, but the lack of impedance control has me nervous.

I suppose the waveguide looks pretty short (under an inch?) so it might not matter much?

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Haven't done anything high speed, but I'm not too worried since it's short. It might not be perfect on the first run, but hopefully it'll work.

8 GHz and multiple traces would be a bit more concerning without impedance control. Hope it works out.

To be clear, my differential pairs are impedance controlled in the sense that their trace/space yield the correct single-ended and differential impedance values at the nominal dielectric permittivity and thickness, but OSH Park doesn't additionally guarantee permittivity and thickness tolerances to guarantee that my nominally-50-ohm traces will be actually-50-ohm traces +/- 10%. That said, I've run the numbers (using the excellent and free Saturn tools [1]) for the stated Er range of 4.2 +/- 0.3, and a little variation in the nominal 7.8 mil thickness, and things still looked OK.

Fingers crossed!

[1] http://www.saturnpcb.com/pcb_toolkit.htm

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