On 2/22/23 9:32 AM, David Needham wrote:
Anyone's guess on the transmission line impedance as described? I've found
calculators for 2 conductors in free space, but I'm scratching my head on
what the Romex covering will do for the dielectric constant. So far my 120
ohms seems like a decent guess, but I wouldn't mind having something better
than my guess.
I'd try an epsilon of 2. Most plastics are around 3 (depending on water
content), but there's some air space too.
Twisted pair with PVC or PTFE insulation has a Z0 of about 100-120 ohms -
You could measure it if you were ambitious. It's a short piece, isn't
it? Way less than a wavelength? it might not make much difference.
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