[TowerTalk] Most reliable way to test coax?

[Brian Alsop]

Here's my take on this.

Unfortunately coax has to really bad to tell that it is with the usual 
instruments available to most of us.

One is generally trying to measure losses in the <1 to maybe 1.5 db 
range.  The uncertainties overwhelm the 0.5 db difference that 
constitutes lossy vs nominal loss.

I once tried using a 50 ohm signal generator and dummy load at the far 
end.  It turns out if one "sweeps" frequency there are cyclic increases 
and decreases in loss due to the usually available voltage sampling 
devices impact and the residual dummy load mismatches/complex impedance 
components. No matter what I tried, I could not get rid of what I think 
were standing waves. Experiment a failure.

So if you suspect coax is old and possibly lossy, stick it on 160 or 80M 
and buy new stuff.

73 de Brian/K3KO








On 9/14/2012 18:01, Wilson Lamb wrote:
>
>
> After all the recent talk about losses and switchboxes, you know how to test by simply leaving the far end open and measuring SWR.
>
> Use your xcvr as a source and test at your operating freq.
>
> The dummy load is a fine power test, but not a good loss test, unless you carefully measure power at both ends
>
> Wilson
>
> W4BOH
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2221 / Virus Database: 2437/5268 - Release Date: 09/14/12
>
>



-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2221 / Virus Database: 2437/5268 - Release Date: 09/14/12