[TowerTalk] measuring old coax, return loss ?

[Ken WA8JXM]

IDK, is "return loss" measurement necessary?

I checked some old coax a few years ago, connected a dummy load to the far
end and used the power meter on my Palstasr tuner to measure the input
power, then moved it to the far end for a measurement. Very little
difference in readings so I assume it was still good.  Am I missing
something?

Ken WA8JXM

On Wed, May 8, 2024 at 2:14 PM Wes Stewart via TowerTalk <
towertalk at contesting.com> wrote:

>  The "best" way depends on what equipment you have to make the
> measurements.  In my best case, I have a DG8SAQ Vector Network Analyzer
> (VNWA) that, with proper calibration will measure the through loss directly.
> My second best is, besides using the VNWA in the reflection mode, is to
> use a DG5MK FA-VA5 one-port Vector Antenna Analyzer.  Take two sets of
> data, one with the far end shorted and one with the far end open.  The use
> AC6LA's ZPlots program to extract the lost and velocity factor, if you care.
> The least accurate, but probably good enough in many cases is to use
> whatever device you have to measure return loss, but the line must be
> terminated in a very highly reflective load, i.e. short or open.  The coax
> loss is them 1/2 of the return loss in dB.  When measuring with a dummy
> load, you don't know what you're measuring, the load, the coax or the
> combination.  A short or open removes one variable.
> In all cases remember that loss and velocity factor (Vp) vary with
> frequency.
> Wes  N7WS
>
>     On Wednesday, May 8, 2024 at 09:43:14 AM MST, Jamie WW3S <
> ww3s at zoominternet.net> wrote:
>
>  What is a good way to test older coax? return loss? I am seeing 12,
> almost 13 db return loss into a dummy load, with about 55 ft of coax,
> good, acceptable or ?!?!?!?!
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