I am testing a long cable run (about 90m). This cable has been used outside and inside, for temporary setups.
I've set up my VNA with the correct values (velocity factor,...) and the distance to fault is correct when I just connect one side to the RF out connector (S11). I don't see any obvious impedance bumps when looking at the DTF measurement. DC resistance of the center conductor and shield is according to the manufacturer specifications for that length. There is no (measurable) DC loss between shield and center. Capacitance is defined at 56pF/m, I measured 5.82nF which seems to correct. So all seems allright.
However, the datasheet specifies 25.8dB loss per 100m at 1Ghz, but I am measuring 43dB loss (S21).
I am wondering if this could be caused by:
- possible moisture in the foam PE dielectric
- other reasons?
Anything I might be missing? Any other tests I could perform?