[TowerTalk] FA-VA5 question

[Lux, Jim]

On 11/5/21 9:35 AM, Dave Sublette wrote:
> I have one of these which I use to check SWR and measure component values.
> I love it.  I know it is capable of doing more.  I just haven't had a need
> to use it any other way.  What I am wondering is, will the thing act as a
> TDR?

Short answer - The device can measure Z vs frequency, and has a USB 
interface, so "maybe"


https://www.box73.de/file_dl/bausaetze/BX-240_FA-VA4_Manual_revised_2017-08.pdf

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.

That is, say you've got a short somewhere.  You look for the frequencies 
where the impedance is close to a short - those are frequencies where 
the cable is a multiple of a half wavelength. Likewise you can look for 
an open, and it's odd multiples of a 1/4 wavelength.


OR, spend $50-70 and get a NanoVNA, which has the TDR function built in.


>
> I have a 200 foot run of half inch Superflex cable buried in a PVC pipe.
> Thanks to a recent lightning strike, It measures shorted at one end of the
> run and open at the other.  If I could get some Idea where the problem is,
> perhaps I could dig it up and repair it without trying to pull and replace
> it.  A fault like this implies to me that there is a clean break somewhere
> and a short somewhere else. With a TDR, I could find the break and repair
> it, then find the short.
>
> Any other thoughts?  Sure would be nice if I could get this repaired before
> winter sets in.
>
> Thanks & 73,
>
> Dave, K4TO
>
> ps -- I know there is a manual for this.  Please don't suggest that I read
> it.  I have nine pieces of equipment to repair and I am up to my ears in
> alligators!
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