Patent US 2883619A

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Patent number US 2883619A
Title Electrical probe
Inventors John Kobbe, Bill Polits
Company Tektronix Inc
Filing date 1956-02-29
Grant date 1959-04-21

The 10th Tektronix patent, this is the famous invention of using lossy coax cable (a resistive center conductor) in a passive probe to dampen reflections and ringing.

John Kobbe said:

Another anticipated problem with passive probe, we knew a signal bounced back and forth so we could not use the standard probe.

While thinking about things to do like some damping resistors. Why not us a fine resistance wire as the center conductor.

This time we really lucked out, it worked better than anticipated. It was even patent-able as was unblanking and [the] sweep circuit.

Until the early 1970s, Tektronix manufactured lossy coax cable in-house using repurposed shoelace weaving machines:

See also