MFJ MFJ-856 User Manual
MFJ-856 Instruction Manual Directional AC Line Noise Meter
INTRODUCTION
Congratulations on purchasing the MFJ-856 AC Line Noise Meter. Like
professional RFI trackers used by utility companies, your MFJ-856 leads you to
trouble spots fast. Here are some important features:
VHF Design: The MFJ-856 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: The 3 element beam is decoupled from case electronics
and head phone 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 MFJ856 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-856, 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
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MFJ-856 Instruction Manual Directional AC Line Noise Meter
friends or fellow club members who are having problems of their own. When
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: 3 element beam
BATTERY INSTALLATION
To install a 9-volt battery, you must first remove the four small Philips head
screws located in the outer corners. Once you have removed the four screws,
you may need to apply a small amount of force to remove the faceplate. After
installing the battery, reposition the faceplate and replace the screws.
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MFJ-856 Instruction Manual Directional AC Line Noise Meter
CONTROLS AND LOCATIONS
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MFJ-852
AC Power-Line
Monitor
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Power
3
MFJ-852
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1. Beam Antenna: 3 elements for maximum sensitivity and best directivity.
Best pick-up sensitivity is obtained when beam is pointed toward the source.
A pronounced null is obtained when beam is 90-degrees to the source.
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.
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