[TowerTalk] FA-VA5 question

[David Gilbert]

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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