[TowerTalk] measuring old coax, return loss ?

[David Hachadorian]

I use an SWR meter or antenna analyzer connected to the unterminated 
coax.  Tune the analyzer to the upper end of its frequency range, e.g. 
30 or 50 MHz.

Loss = 10 Log ((SWR+1)/(SWR-1))

After determining the loss in the OLD cable, you can look up the loss in 
the equivalent length of NEW cable, and decide whether you can live with 
the difference.

This method can even be used with an antenna connected at the far end.  
Just tune the analyzer for maximum SWR in the 20-50 MHz frequency range 
and do the calculation at that frequency.  By doing the measurement at 
the frequency of max SWR, the antenna is essentially disconnected.  By 
using the analyzer at the upper end of its frequency range, inaccuracy 
in the measurement of high values of SWR are minimized.

Dave Hachadorian, K6LL
Yuma, AZ



On 5/8/2024 9:42 AM, Jamie WW3S 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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