On 10/21/2021 1:52 PM, KD7JYK DM09 wrote:
When we had standards, it was 52. Once standard became "nominal", it
was rounded down in print to cover sloppiness/ease in manufacturing.
More likely because Zo and VF of ALL transmission lines vary with
frequency. It's predicted by the wave equations. Several years ago, I
measured Zo, VF, and Attenuation vs frequency for all of the
transmission line types used in the HF transmitting chokes in my
Cookbook. Harbour Industries MIL-spec RG400, for example, is 52 ohms
around 1.2 MHz, with VF just below 0.69; at 50 MHz, it's 50 ohms and 0.722.
Here's a tutorial I wrote for guys working in pro audio who thought
(mistakenly) that long audio cables in performance venues ought to be
viewed as transmission lines.
http://k9yc.com/TransLines-LowFreq.pdf
73, Jim K9YC
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