On 5/2/2020 3:43 PM, VE6WZ_Steve wrote:
I made a number of measurements of my Beverages last summer including using TDR
to estimate physical length. This depends on knowing the VF of the wire.
However, If you know the physical length length, the using the TDR function you
should be able to derive the VF of the BOG.
Yes, BUT -- you probably know that VF, Zo, and attenuation all vary with
frequency. Most analyzers measure VF at VHF/UHF, which is where Zo and
VF converge. On 160, VF is typically ~3% slower and Zo is typically ~3%
higher. These characteristics can be obtained by sweeping a known length
with the far end open and shorted, exporting the data to AC6LA's ZPlots
Excel spreadsheet, which will compute and plot the data. Very good
calibration of the analyzer is needed for accurate results.
73, Jim K9YC
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|