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The TDR is a project by Stan W0SJ that was published in QST in 2021. This is a very useful tool for testing coax cable, so I made a PCB. Since there are only a few components, the boards were assembled in China. They are provided fully assembled.

You can install SMA connectors directly to the PCB or use the 2 holes to mount a short coax cable. The coax cable capacitance will influence the pulse duration as the 74HC inputs are very high impedance. J1 is meant to be mounted directly to the front of the scope to minimize this effect.

J1 – Scope input TRIGGER
J2 – Scope input Amplitude
J3 – coax cable being tested.

Apply >+7VDC for the internal 3 terminal regulator to be happy.

The PCB is made to fit a small metal enclosure like the Bid CU-3000 available from Digikey or other distributors.