On 1/12/2020 3:55 PM, Michael Tope wrote:
FWIW, the lowest frequency I used was about 2 MHz. The 140 KHz was the
frequency difference (not the absolute frequency) between adjacent
points where the impedance came back around to the same zero reactance
crossing point on the Smith chart. According to the graph in your
paper, the difference between the Vf at 2 MHz and the asymptote would
be about 2%. That was plenty close for my purposes (I just wanted to
make sure the length of the subject reel was close to what was advertised).
Yes. The data in the tutorial is from the Teflon version of Commscope
3227, which has a #10 solid copper center, a robust tinned copper braid,
and a robust Al foil between the braid and the dielectric. Because it's
Teflon (to meet indoor UL flame spread ratings) the o.d. of shield is a
bit less than 3227 (RG8/213 size), making it slightly lossier than 3227.
The Teflon cable carries a different part number, something in a
5200-series. Both cables are probably obsolete -- a colleague bought a
bunch of both cables from a bankruptcy during the dot com bust in the
early 2000s.
73, Jim K9YC
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