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Table of Contents

1. Ground Loops ..... What are they?
2. What causes Ground Loops?
3. What are some common effects of Ground Loops?
4. What relief is there for Ground Loop problems?
5. Hum Bars - What Causes Them in Video Systems?

Ground Loops .... What are they?

Ground Loops are conditions set up by 2 or more ground paths over which AC power and/or signals are passed. 

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What causes Ground Loops?

1. Occasionally, the AC power develops voltage over a ground path shared with an audio, video or other signal.  This voltage combines with the signal, creating a ground loop condition.

2. Cable Modems, Cable TV and FM and apartment TV/FM distribution systems often have ground loop problems because the signal source (cable company) ground and  your modem or TV/FM receiver ground are at different voltages.  Current flows between these grounds over the cable shield.

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What are some common effects of Ground Loops?

Audio systems may develop serious hum.

In video or television, this hum may show up as bars across the screen. These bars my be stationary, or may move up or down.

Other equipment may perform erratically

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What relief is there for Ground Loop problems?

1. Many times cleaning up equipment grounding will eliminate a Ground Loop problem.

All audio, video or other signal grounds should be tied to the same grounding terminal.   When there are multiple pieces of equipment, all equipment grounds should connect to the same ground terminal.

When this is impractical - connect as many equipments as possible to 1 ground terminal.  
Check out equipment performance. 
With luck, you will have isolated the interference causing ground.

2. Often AC power ground loops can be solved with installation of an AC power
Isolation Transformer to provide electricity for affected equipment.  This is particularly effective for Industrial instrumentation, process control or point of sale (POS) stations.

If AC power is suspect and somewhat erratic, a Voltage Regulator can be extremely effective.
Our Kleen*Line Regulators not only isolate ground loops, but also clean up AC power and hold supplied operating voltage to a constant voltage level.

3. Cable Modem, Cable TV/FM and community TV system ground loops can be eliminated by installation of a Cable Isolator. In addition to solving the ground loop problem, Electronic Specialists Cable Isolator provides a 2,500 volt surge suppressor protective shield for your equipment.

Usually a single Cable Isolator at the point of cable entry from the street will cure the problem. If this is ineffective - experiment;  Install the Cable Isolator directly at equipments connected to this cable.  More than likely, a single unit will eliminate the ground loop, curing the problem.

On rare occasions, a second or third Cable Isolator is required.  Again, experiment to locate the most efficacious installation points for solution of your ground loop interference problem.

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Hum Bars - What Causes Them in Video Systems?

Video Hum Bars are usually caused by inductive pick up in transmission cables between camera and monitor or selector panel.

Technically this is not a ground loop problem, but it behaves the same, and is usually called a ground loop problem by both technicians and equipment users.

These transmission cables are most often co-axial cables, with the shield  introducing the inductive hum pick-up.

Our Hum Buckers have been very effective at solving this problem.

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