Ground loop!

Ok, here's the scene : you get your satellite modem linked successfully, but the PVC on your frame relay network REFUSES to come up. All settings on both sides are correct, so what's the problem?

After extensive troubleshooting, it was discovered that the satellite dish was installed on top of a shipping container. That container was attached to 26 more. It just so happens that the electrician onsite started a grounding project where he was strapping the containers together with copper to put them all at the same potential.

However, this was not the same potential that the trailer housing the satellite equipment was in. This slight difference in potential was enough to corrupt all data on the satellite cables, preventing any communications.

Moving the dish onto physical ground fixed the problem. Now I'm facing a similar problem, troubleshooting continues tomorrow.

Anyone else have a weird ground fault story?

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Comments

tiersten

You might be surprised at the voltage difference if you actually go and check it. Its normally not that slight...

Satellite installations usually have certain issues with different ground potentials because the dish is earth nearby and your receiver gear is at the end of a looooooong piece of coax which is also earthed.

Its no less annoying to diagnose the actual cause in audio equipment although you can usually tell its a ground loop problem because of the charactistic 50/60Hz hum. You end up with really suspicious tricks from an electrical point of view like isolators and disconnecting the shields etc...

dtlokee

Yeah issues with grounding between buildings is very common, this is one of the reason Fiber is a good choice. Is it possible for the electrician to install a bond between the shipping containers and the building's electrical service?

learningtofly22

tiersten wrote:

You might be surprised at the voltage difference if you actually go and check it. Its normally not that slight...

Actually, it was very slight in this case, about 500 mV. Doesn't take much to disrupt a signal once it's L band.

dtlokee wrote:

Yeah issues with grounding between buildings is very common, this is one of the reason Fiber is a good choice. Is it possible for the electrician to install a bond between the shipping containers and the building's electrical service?

Fiber is an option, but pricey. Best case is to just get the dish's skid placed on solid ground so it's never at the mercy of metal/ground problems in the future.