There is one big advantage of the return loss test, besides measuring double
the loss (down and back) which gives a more sensitive test... and that is
you don't have to go to the far end of the cable. I can test most of my
main cables here from the shack by just opening the remote switch and
putting a bit of power down the line... makes for a quick and easy test with
built in instrumentation, just flip a switch and its basically done.
David Robbins K1TTT
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: firstname.lastname@example.org [mailto:email@example.com]
> Sent: Thursday, December 10, 2009 21:03
> To: firstname.lastname@example.org
> Subject: Re: [TowerTalk] Resistance of RG-8 cable?
> K1TTT wrote...
> > I think a better test is a return loss test at 10m, leave the
> > far end either open or shorted and measure the reflected power or swr,
> > higher it is the better the cable.
> Or, put a good dummy load at the far end, and measure the RF power out of
> exciter into the cable. Now, without changing RF level, move the power
> meter down
> to the dummy load end and measure the power being delivered to the dummy
> Now you've measured the actual loss in the cable. Compare it with the
> manufacturer's specified value, and you know if it has degraded. If the
> resulting loss
> is something you want to live with, keep using the cable!
> Remember, the loss of brand-new, high-quality cable IS NOT zero!
> George T Daughters, K6GT
> CU in the California QSO Party (CQP)
> October 2-3, 2010
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