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Old 01-17-2009, 11:39 PM   #1
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Phanton Voltage from Satalite


I spent hours chasing down the reason for reading about 9v to ground from conductors in the attic that should have been dead. (they run fairly close to the satellite cable) I finally decided that it is the satellite system cable that is causing phantom voltage on the line. The satellite system puts out about 50v at the satellite unit.

The satellite dish was "professionally" installed by direct the direct tv people. So I am not sure it is properly grounded (can find no evidence of a ground connection running down from the dish). The dish is currently inaccessable safely. It is 25 feet up on top of a icey room.

I am wondering if this is normal for a statile connection to be leaking voltage like this or if this is a problem due to an improper ground / bond connection.

On some circuits that are not as close to the satellite cable, but are completely disconnected, I still read about 4 or 5 volts on them. This is with my Idea RMS meter. I brought my meter home tongiht and tested some outlets I have wired up, but are disconnected at the panel (not connected at all, no ground connected). And I read around .2 to .4 volts in my house. Nothing close even to the lower 4 volt reading I got at my parrents house.

Any ideas what I would see this much voltage all over the place on dead cirucits in there house? Could it have anything to do with all the knob and tube in the house?

Thanks very much,

Jamie

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Old 01-17-2009, 11:50 PM   #2
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Phanton Voltage from Satalite


I would try to find out if the dish is grounded, just for safety's sake. But, induced voltages can be several volts especially on long runs. In your romex, the two wires are very close together, and so the induced voltage is nearly equal, so you won't read a large voltage between them. In K & T, the wires are separated by several inches, so the potential difference can be greater. Also, in dry air charges can build up like a capacitor and appear as a voltage on a cable. Usually, these phantom voltages cannot drive enough current be dangerous or even noticeable to touch.

But, it is worth investigating just in case.

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Old 01-18-2009, 12:01 AM   #3
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Phanton Voltage from Satalite


check the coax termination, the shield in the cable is usualy the ground for cable systems if its loose it might need to be remade. The shield should cancel out any induced voltage from other power sources. In any case when you are unsure about voltage the best thing to do is test with an analog meter like a wiggy because digital meters can give you a false positive from time to time. I have seen it happen on machinery where the fluke meter says voltage is there but a wiggy says nope, you cant fool it.
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Old 01-18-2009, 12:06 AM   #4
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Phanton Voltage from Satalite


Quote:
Originally Posted by InPhase277 View Post
I would try to find out if the dish is grounded, just for safety's sake. But, induced voltages can be several volts especially on long runs. In your romex, the two wires are very close together, and so the induced voltage is nearly equal, so you won't read a large voltage between them. In K & T, the wires are separated by several inches, so the potential difference can be greater. Also, in dry air charges can build up like a capacitor and appear as a voltage on a cable. Usually, these phantom voltages cannot drive enough current be dangerous or even noticeable to touch.

But, it is worth investigating just in case.
Is it possible to ground the satellite via the coax cable or does the ground have to be connected directly to the satellite dish frame?

Is there any type of meter that would help me in the future to be able to more easily tell if I am seeing phantom voltage or if I am seeing line voltage, at a lower voltage, due to say a loose neutral that was attached onto the circuit fed by a live circuit. (I am being really careful, but there are tons of buried wire nuts in the walls with no boxes). Even worse are the connections made inside the walls with only some electrical tape holding the connections together.

Thanks
Jamie
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Old 01-18-2009, 12:14 AM   #5
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Phanton Voltage from Satalite


Quote:
Originally Posted by jamiedolan View Post
Is it possible to ground the satellite via the coax cable or does the ground have to be connected directly to the satellite dish frame?

Quote:
Originally Posted by ctsmiths View Post
check the coax termination, the shield in the cable is usualy the ground for cable systems if its loose it might need to be remade. The shield should cancel out any induced voltage from other power sources. In any case when you are unsure about voltage the best thing to do is test with an analog meter like a wiggy because digital meters can give you a false positive from time to time. I have seen it happen on machinery where the fluke meter says voltage is there but a wiggy says nope, you cant fool it.
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Old 01-18-2009, 12:15 AM   #6
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Phanton Voltage from Satalite


you forgot 6
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Old 01-18-2009, 12:42 AM   #7
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Phanton Voltage from Satalite


Quote:
Originally Posted by jamiedolan View Post
Is it possible to ground the satellite via the coax cable or does the ground have to be connected directly to the satellite dish frame?

Is there any type of meter that would help me in the future to be able to more easily tell if I am seeing phantom voltage or if I am seeing line voltage, at a lower voltage, due to say a loose neutral that was attached onto the circuit fed by a live circuit. (I am being really careful, but there are tons of buried wire nuts in the walls with no boxes). Even worse are the connections made inside the walls with only some electrical tape holding the connections together.

Thanks
Jamie
Your supposed to ground the coax and the frame.
I'd run it to the system ground with wire depending on the length. Normal is 14-10 awg.
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Old 01-18-2009, 12:54 AM   #8
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Phanton Voltage from Satalite


Often the coax that is used for satellite has a ground wire embedded in the jacket. But, I would not use a wire smaller than #10 copper. Run it to the dish and connect it. Then connect it at the coax terminal block (if used) and on to a good electrical ground. This can be at the panel, or meter socket, or GEC.
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Old 01-18-2009, 12:58 AM   #9
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Quote:
Originally Posted by rgsgww View Post
Your supposed to ground the coax and the frame.
I'd run it to the system ground with wire depending on the length. Normal is 14-10 awg.
So the outside (silver metal mesh) part is suppose to be grounded?

Once stuff thaws no problem bonding directly to the dish. If it is that important to get done now, I think we would need to setup scaffold or get a bucket truck out.

Thanks
Jamie
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Old 01-18-2009, 01:02 AM   #10
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Phanton Voltage from Satalite


Quote:
Originally Posted by InPhase277 View Post
Often the coax that is used for satellite has a ground wire embedded in the jacket. But, I would not use a wire smaller than #10 copper. Run it to the dish and connect it. Then connect it at the coax terminal block (if used) and on to a good electrical ground. This can be at the panel, or meter socket, or GEC.
Thanks, I will look at the cables and see if they have that extra cable in them. Then get on the roof as soon as possible to get the dish grounded . bonded.

Do you think this is urgent enough to getting the satellite grounded correctly that I should try and find someone that will give out with a bucket lift and add the clamp and the wire? later in the spring once stuff is melted and dry it's not a problem to go up there. It is a death trap with the icy roof.

Jamie
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Old 01-18-2009, 01:05 AM   #11
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Phanton Voltage from Satalite


Quote:
Originally Posted by jamiedolan View Post
So the outside (silver metal mesh) part is suppose to be grounded?

Once stuff thaws no problem bonding directly to the dish. If it is that important to get done now, I think we would need to setup scaffold or get a bucket truck out.

Thanks
Jamie

Some ask for it...some don't. It probably doesn't.

It wouldn't hurt to check in spring.

Use at least 10.
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Old 01-18-2009, 01:06 AM   #12
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Phanton Voltage from Satalite


I doubt that it will be a problem but that is your call. I would wait myself.
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Old 01-18-2009, 01:06 AM   #13
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Do you think this is urgent enough to getting the satellite grounded...

Jamie
Depends. Probably not that urgent. Are you reading a significant voltage from the coax sheath to ground? It should be nearly zero if the coax is grounded properly.
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Old 01-18-2009, 01:12 AM   #14
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Phanton Voltage from Satalite


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Depends. Probably not that urgent. Are you reading a significant voltage from the coax sheath to ground? It should be nearly zero if the coax is grounded properly.

Yes, around 50volts. Which is the same reading I get off of the back of the satellite unit without the cable connected. It appears all the voltage on the line is being generated by the satellite box and then Phantomed out elsewhere, including my 9 volts on the knob and tube :-). But yet that is about 50v. Enough to physically light up one of those little bulb testers.

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Old 01-18-2009, 01:17 AM   #15
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Phanton Voltage from Satalite


you're getting a voltage reading on you water fixtures?

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