[Lowfer] receive antenna transmission line maintenance

[Dexter McIntyre W4DEX]

That was electrolysis corrosion Pat.  Very much different than sealing 
current.

Dex

pbunn wrote:
> 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
>
> "Douglas D. Williams" <kb4oer at gmail.com> wrote:
>
>
> Interesting thread. I didn't know any of this.
>
> I wonder if the DC current present on outdoor active antennas helps or
> hinders corrosion?
>
>
> While were on the subject of antenna maintenance, how do you guys
> weatherproof outdoor BNC connections? I've been using this black silly
> putty like substance called "coax seal". It comes in small rolls.
> Works well for weatherproofing, but is difficult and messy to remove
> later on.
>
> 73, Doug KB4OER
>
>
>
> On Fri, Jan 25, 2013 at 10:27 PM, Michael Sapp <wa3tts at verizon.net> wrote:
>   
>> Stan, W1LE wrote:
>>     
>>> Do you think a light coating of silicone dielectric grease would more
>>> permanently solve that corrosion problem ?
>>>       
>>> Two dissimilar metals, plus the electrolyte acid rain = galvanic corrosion.
>>> The grease would keep out the acid rain/moisture.
>>>       
>>> I would even consider the grease treatment and a waterproof taping
>>> on all coaxial joints exposed to the elements.
>>>       
>>> Stan, W1LE    Stan, I suppose it can't hurt. Rad Shack & others sell the male cable F connectorspre-silicone-gelled. IMHO it seems in part to stem from the low signal level nature ofa feedline for a passive rx antenna---not enough uVs and pico-amps to overcome the residual resistanceat the F center pin interface that eventually builds up.  Sometimes it seems thermal expansion/contractioninduced with weather temp changes cause the RG6 center conductor to move slightly and change resistanceat the physical connector interface.    I know if I give the rx antenna transmission lines a mild jolt once a week that it solves the problem. If I ran my AL-82 amp on HF more often, the induced milliwatts into the rx antenna would likely be enough power to prevent the issue. John, XIQ, mentioned to me in an e-mail a few minutes ago he turns his rx antenna towards his tx antenna during  tuneup to clean the relay contacts on his rx system as a similar preventative measure....    Likely a goo
>>>       
>  d
>   
>>   reason for me to put some relays in the receive antenna transformer boxes for directional switching---the regularDC power cycling of the relays with a DC up the coax arrangement would be an automatic maintenance solution....Perhaps others on the list will share their experiences on the subject.....73  Mike wa3tts
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