[TowerTalk] Need help estimating cable length of DXE 400 MAX

[Jim Brown]

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