AT&T 518-600-016 manual Solutions to Radio- Frequency Interference Problems

Solutions to Radio- Frequency Interference Problems

placed in areas where a high electromagnetic field strength exists. Leading causes of interference include AM and FM radio station transmitters, television station transmitters, induction heaters, and motors (with commutators) of 0.25 horsepower (200 watts) or greater. Small tools with universal motors are generally not a

problem when they operate on separate power lines. Motors without commutators generally do not cause interference.

Field strengths below 2 volts per meter are unlikely to cause interference. Field strength can be measured by a tunable meter such as the Model R-70 meter manufactured by Electro-Metrics Division, or broadband meters such as the HOLADAY™ HI-3001 meter or Model EFS-1 meter manufactured by Instruments for Industry, Inc.

You can estimate the field strength produced by radio transmitters by dividing the square root of the emitted power in kilowatts by the distance from the atenna in kilometers. The result yields the approximate field strength in volts per meter and is relatively accurate for distances greater than about half a wavelength (150 meters for a frequency of 1000 KHz).

To reduce or eliminate radio-frequency interference problems from nearby induction heaters or 0.25 horsepower motors, either move the equipment causing the problem or move the MERLIN II system control unit to a different location.

To reduce or eliminate radio-frequency interference problems from nearby radio station antennas, choose from among the following solutions:

●Do not run MERLIN II system station wire in the same conduit as ac cable, or next to ac circuits if the station wire is exposed. If possible, do not cross station wire

2-10 System Grounding Requirements