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post #1 of 8 Old 04-19-2013, 11:47 PM - Thread Starter
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I have a 30ft coaxial cable. Shielding and main conductor are isolated from each other at both ends. Cable is not connected to anything at either of the ends. One of the ends is on the roof and the other is in my room. The reason for being disconnected at both ends is preventive against lightning strike. It has happened three times, as far as I can remember, that when I touched the cable in the morning I got a slight shock like the one you get in winters by touching metallic items. Moreover, when the conductor of this cable is brought in contact with something metallic item, a visible discharge is clearly seen. The end on the roof, though not connected to anything, has the man conductor peeled off for about 27 cm and serves as an antenna for a radio receiver. I have a few questions:

1. Why is it happening?
2. Are the two conductors and the insulation between them are acting as a capacitor and storing electrical charge from atmosphere?
3. What can be done to prevent it as I need the peeled off end to serve as antenna, which otherwise is doing well as an antenna?

I will be grateful for all the help I could get. Thanks.
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post #2 of 8 Old 04-20-2013, 05:58 AM
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Install a grounding block
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post #3 of 8 Old 04-20-2013, 07:24 AM
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Buildup of static electricity. As Ratman wrote, "Install a grounding block."

CIAO!

Ed N.
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post #4 of 8 Old 04-20-2013, 08:25 AM
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Or wear rubber gloves.
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post #5 of 8 Old 04-20-2013, 11:58 AM
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Just as shuffling your feet across carpet, static electricity is built up as wind passes over not only the short length of exposed wire, but ALSO the much longer length of coax. A Ground Block is a NEC Code Requirement, the lack of which your insurance company could make a case for non-coverage....so JUST DO IT....for safe of sanity, safety and will also drain off the static electricity being built up on the outside of the coax, protecting your equipment from everyday damage.

BTW: Disconnecting the coax did NOTHING to protect you against direct Lightning strikes....A Grounding Block provides a path of least resistance to ground...outdoors...where it hopefully causes the least damage...
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post #6 of 8 Old 04-20-2013, 01:01 PM
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Quote:
... A Ground Block is a NEC Code Requirement, the lack of which your insurance company could make a case for non-coverage......

I have participated in hundreds of grounding threads over the years but not only have I never read of a single substantiated case of an insurance company using failure to ground as a basis or pretense for not paying a damage claim. I have also never read of any substantiated case of an insurance company even threatening to do so. I've also been hired to make a couple of damage estimates for insurance companies and in neither case did the insurance company ask me if the system was grounded. One did ask me if I had performed a "litmus paper test", and I thought, "Yeah, I did one of those in high school chemistry class but I don't remember what I was testing for", but even though I readily acknowledged that I had not, they paid the generously estimated damage claim... including three weeks of receiver rental paid to me while the customer unit was out for repair.
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post #7 of 8 Old 04-20-2013, 01:51 PM
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But........ back to the opening post.
1) a "makeshift" antenna
2) not properly grounded
3) supposedly three lightning strikes over time

In order to resolve:
1) install a real antenna
2) properly ground the antenna, mast and coax

Most notable:
No matter how well you install and ground your antenna, no matter how hard you pray, even a nearby lightning stike can cause an issue. But, static buildup is the likely cause of your issue.
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post #8 of 8 Old 04-21-2013, 10:08 AM
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For the OP:

Click here for a thread on grounding. Several links and graphics in that thread.
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