MFJ MFJ-852 User Manual

MFJ-852 Instruction Manual

AC Line Noise Meter

INTRODUCTION

Congratulations on purchasing the MFJ-852 AC Line Noise Meter. Like professional RFI trackers used by utility companies, your MFJ-852 leads you to trouble spots fast. Here are some important features:

VHF Design: The MFJ-852 operates at 135 MHz where antenna length is short, on-air interference is minimal, and RFI is localized easily for accurate tracking.

Wideband IF: 100 kHz IF bandwidth provides optimized noise sampling.

1 uV Sensitivity: Picks up all noise signatures, weak or strong.

Semi-Log Metering: Semi-log metering system covers a wide signal range without the need for add-on step attenuators.

Balanced Antenna: Built-in collapsible dipole is decoupled from case electronics and headphone leads to deliver a clearly-defined null. Locates RFI sources easily.

Audio Jack: Plug in stereo or mono type headphones for audible monitoring, or connect a portable cassette recorder to make sound recordings for later analysis. Many powerline faults have identifiable noise signatures that experienced powerline technicians can identify easily--even over the phone!

Battery Indicator: LED power indicator also monitors battery status--let's you know when it's time to replace the battery before the meter stops working properly.

Tracks Many Types of RFI: In addition to transmission line noises, the MFJ852 also ferrets out residential and industrial noise sources such as electric fence arcs, sparking power equipment, poorly suppressed specialty lighting, and much more. Give your claims added credibility by showing the owners of defective equipment where the problem is being generated--and letting them hear what it actually sounds like!

Fully Portable: Compact hand-held size and built-in battery power let you to explore freely in search of trouble spots.

Always Available: Many power-related noise problems are intermittent and rarely occur when power company engineers are in the neighborhood with the RFI truck. With the MFJ-852, you can capture the data you need instantly-- when its happening!

Be a detective and put the fun back into Ham Radio! In addition to solving problems in your own neighborhood, this is a great way to lend assistance to friends or fellow club members who are having problems of their own. When

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MFJ-852 Instruction Manual

AC Line Noise Meter

power companies get a concise description of the noise and a specific pole number, you get much faster service!

SPECIFICATIONS

Operating Frequency:	135 MHz (internally tunable)
Receiver Sensitivity:	.3 uV for audible detection
Meter Sensitivity:	<2 uV for usable deflection
Meter Range:	50 dB, semi-log response
Receiver IF Bandpass:	100 kHz
Audio Output:	Fixed, headphone level (line level for record)
Power Source:	Self-contained, 9 volt flatpack battery
Current Drain:	30 mA
Antenna:	Choke-balun-decoupled collapsible dipole

CONTROLS AND LOCATIONS

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MFJ-852 4

AC Power-Line

Monitor

2 Power

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1.Collapsible Antenna: Extend full length for maximum sensitivity and best directivity. Best pick-up sensitivity is obtained when dipole is broadside to the source. A pronounced null is obtained when dipole is 90-degrees to the

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MFJ-852 Instruction Manual

AC Line Noise Meter

source. Length may be shortened to reduce sensitivity for extremely strong RFI sources.

2.Headphone Jack: Connect standard stereo or monaural type headphones using a 3.5 mm plug. Also, the headphone jack may be used to feed a portable cassette recorder (line-level input)--or even a portable oscilloscope for complex waveform analysis.

3.Power Switch: Press in to apply power to unit.

4.Power/Battery LED: Illuminates when power is applied, extinguishes when battery voltage drops to a marginal level.

5.Meter: Semi-log metering system displays wide signal range with more resolution at the low end of the scale.

HUNTING DOWN NOISE ON THE POWER LINES

Most utility-line noises comes from arcing or corona. Arcing (or sparking) happens when 60 Hz AC swings to its extreme plus or minus value. This can induce voltage in associated wiring and hardware that arcs across an imperfect insulating medium. The resulting RFI often appears as a 120 Hz AM modulated buzz or hum. Corona happens when a discharge occurs in ionized air rather than through a discharge path to ground. Corona may produce a more constant noise, frying, or even a high-pitched whine.

+Arc +
60-Hz	Off-Air RFI
Energy on	120 Hz Buzz
AC line	-
-Arc

The distance powerline RFI propagates usually drops rapidly as monitoring frequency increases. A noise that's received for a mile or more in the AM broadcast band may only be detectable for a hundred feet or so at 130 MHz. That's why utility companies use handheld VHF-AM receivers instead of HF radios to zero in on line noise problems.

RFI
Strength	10 MHz	1 MHz
130 MHz
	Distance from Fault

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