[Lowfer] receive antenna transmission line maintenance

[Douglas D. Williams]

Good point, Todd.

I am currently using LMR-240 DB (direct bury) for my outdoor run.

I really like LMR-195 for indoor patch cables.

73, Doug KB4OER



On Sat, Jan 26, 2013 at 3:41 PM,  <ToddRoberts2001 at aol.com> wrote:
> Thanks for the report on the corrosion problem with aluminum coax  shield
> made worse when a DC bias is applied like when powering an active whip
> outdoors through the downlead.
>
> It makes me think it would be best to avoid using any coax with  aluminum
> shield if you expect to use it for powering a remote active whip  outdoors.
>
> I always recommend using a full-size RG213 coax with a remote active  whip.
> Much better copper braid shielding compared to consumer-grade RG58 and
> should be no
> corrosion problems like can happen with aluminum shielded coax.
>
> 73 - Todd WD4NGG
>
> In a message dated 1/26/2013 10:03:19 A.M. Eastern Standard Time,
> pbunn at matrixei.com writes:
>
> It makes corrosion worse. About a month ago I came in and found the power
> supply led off on my DC coupler. I figured the power supply had died but
> when I  unplugged the coax it was OK, so then I knew I was looking at a short
> at the  probe or in the coax. Looking at the way the probe circuit works, I
> didn't see a  way a failed transistor could result in a short  that low in
> resistance.
>
> I emailed Jack Smith and asked hid opinion and he said 90 %  likely that I
> had  a coax problem and the DC bias would corrode a breach in  the shield.
> After a couple hours with the multimeter, I found a pinhole in a  buried
> section of the Belden quad shield. Just as Jack had indicated, the DC  current
> had caused the aluminum shield to turn to powder for s couple of feet. I
> ended up replacing the entire 300 foot run with new  cable.
>
> Pat
> N4LTA
>
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