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oscilloscope probe cable?

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freda:
would i be right to assume oscilloscope probe cable is made of RG174 ?
table https://web.archive.org/web/20120511024343/http://belden.com/resourcecenter/tools/cablefinder/upload/06-3_15.pdf
RG174 jacket OD 0.11inch
i actually measure closer to 0.12in
so seems about right.... ?

alm:
No, passive high-impedance scope probes use resistive coax with generally some sort of Nichrome center conductor, which I don't think is generally available from the cable manufacturers. See page 15 of Tektronix Oscilloscope Probe Circuits, a publication that while old is probably the most thorough technical description of oscilloscope probes. If you read the pages leading up to it, it explains why ordinary coax wouldn't perform well at all, because the oscilloscope input is far from 50 Ohm. Or see this video.

If you were building a probe designed to work into a 50 Ohm input, like what is generally called a resistive divider probe, or an active probe driving 50 Ohms, then you would use regular 50 Ohm coax like RG-174 or even thinner.

bdunham7:
If it is a probe designed to be used with a 50R input, then perhaps.  If it is a 10X or 100X probe for a 1M input, then it should be a specialty resistive cable designed for low group delay dispersion rather than low amplitude loss.  If it is a 1X only probe, then I don't know and it likely doesn't matter very much.

freda:
thanks for the reading material. looks good.

yeah i was thinking about making my own higher voltage probe, so what cable to use came to mind.
might be good to just get a cheap probe off aliexpres or something and cut that.

alm:
What kind of bandwidth are you aiming for? You will likely need to modify the compensation box on the scope side. Finding an older, bigger probe with a larger compensation box might be easier to modify.

Nichrome wire does not solder well at all. It's normally crimped instead of soldered.

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