Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

Albert Otten

On Mon, Apr 29, 2019 at 10:50 AM, Richard Knoppow wrote:

Where does it show the speed of light in a vacuum? The TDR
should be calibrated to the speed of light (electricity) in the
cable. For 50 Ohm cable its about 66% of c. Varies with the
impedance of the cable. If you know the physical length of the
cable you can determine both its impedance and the velocity from it.

On 4/29/2019 1:26 AM, Albert Otten wrote:
Interesting stuff Dennis! I have to look at it in more detail. I consider
repeating these tests since I have both Tek cables, though I don't have
quality SMA-BNC adapters.
Most remarkable is the slow speed of light in vacuum in the USA ;-)
Richard Knoppow
The document says: "The speed of light in a vacuum is 224844343.5 m/Sec= 0.2248m/nSec. "
I guess Dennis already used some kind of velocity factor here. But this makes his following derivation invalid:
"The Velocity Factor (the speed the signal travels in the dielectric of this cable) is VF = 2* 36.0in * 0.0254m/in * 4.4475nSec/m/9.0nSec ~ 0.90. "


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