That works, but if the problem is approximately short or an open, there
is an easier way to achieve a kind of manual TDR:
1. Take readings with the FA-VA5 at three different frequencies chosen
to represent something between a quarter wavelength and half wavelength
compared with the length of the transmission line.
2. Load those readings and other relevant info (frequency, type of
feedline) into TLW, the free application that comes with the ARRL
Antenna Book.
3. Tell TLW that your transmission line is a bit longer than it
actually is, and then use TLW to plot the resistance and reactance along
the line.
4. Look for the spot on the three curves that has the same values at
the same distance on the line.
It works. I've done it to find a connector that had arc'd and the
resolution was amazing ... less than a foot. The concept is actually
viable for problems other than a short or an open ... it's just more
difficult to spot on the plots
73,
Dave AB7E
On 11/5/2021 11:17 AM, Jim Brown wrote:
On 11/5/2021 9:51 AM, Lux, Jim wrote:
Manual doesn't describe a TDR function, nor the USB interface, BUT,
it does offer that by looking for resonant frequencies, you can
measure the length of a cable.
TDR can be accomplished by using DG8SAQ's VNWA software on the
exported file. Perform the widest possible sweep, save the file per
the manual, and import in that software.
73, Jim K9YC
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