[TowerTalk] TowerTalk Digest, Vol 160, Issue 33

[Jim Brown]

On Tue,4/12/2016 12:17 PM, David Aslin G3WGN wrote:
> I do have a short length (maybe 60ft or so) of properly stored near-new LDF4-50 so I can use that as the baseline.
> Anyone actually attempted impedance or another measurement to check for performance change?

Hi Dave,

The best way I know of to measure coax parameters is to do an open and 
short Z measurement with a vector analyzer and import both into ZPlots, 
which is an Excel spreadsheet. You also need to enter the length if you 
want Vf and attenuation/ft (or /m). ZPlots will yield a graph of Zo, Vf, 
and attenuation vs. frequency.

My weapon of choice for measurement is DG8SAQ-designed VNWA, built and 
sold in the UK by SDR Kits. About $700 shipped to the US with 
calibration kit. It also does excellent TDR by sweeping over whatever 
frequency range you choose and taking the inverse FFT. For best detail 
(and to see "little" issues, I usually sweep 100-500 MHz. For even 
better detail, sweep 600-1,300 MHz.

73, Jim K9YC

73, Jim K9YC