MFJ MFJ-249 - Battery Installation

MEFJ-249 SWR Analyzer Instruction Manual
POWERING THE MFJ-249
The MFJ-249 requires between 8 and 18 volts for proper operation. Any power supply used
with the MFJ-249 must be capable of supplying 200mA of current. An optional power supply,
the MFJ-1312B, is available from MFJ for $12.95.
The MFJ-249 has a standard 2.1 mm female receptacle on the top right edge of the case. This
jack is labeled "12VDC" and has the word "POWER" near it. A pictorial polarity marking
appears on the case near the power jack. The outside conductor of the plug must connect to
the negative supply voltage and the center conductor of the plug : :ust connect to the positive
voltage. The internal battery pack is automatically disconnected when an external power plug
is inserted in this jack. :
SWR measurement will be inaccurate when the supply voltage faiis below 7 volts. To avoid
false readings this unit has a low battery warning indication that will appear on the counter
display if the supply voltage drops below acceptable levels.
Warning: Never apply AC, unfiltered or incorrectly polarized DC to this jack. Peak voltage
must never exceed 18 volts.
BATTERY INSTALLATION
If batteries are used, they must be installed by removing the 8 phillips head screws on each side
of the case. The eight batteries fit in two separate battery holders with the positive terminal of
the batteries positioned toward the round fixed connection, and the negative terminals toward
the springs of the battery holder.
The battery case has two external terminals that connect to a "pivtail" that has two terminals
on it. This connector looks like the type used for 9 volt transistor radio batteries and connects
in the same way. Do not attempt to use 9 volt batteries with this unit. After the batteries are
installed in the plastic holders and the connections are made to tne battery packs, the battery
holders can be slid directly into the chrome retaining clips on the cover.
MFJ recommends the use of ALKALINE AA (or rechargeable nicad) cells to reduce the risk
of equipment damage from battery leakage. Avoid leaving any batteries in this unit during
periods of extended storage. Remove weak batteries immediately’
Carefully check the following:
* The battery packs are positioned so that they do not interfere with any internal parts of the
MFJ-249. .
* The leads are positioned to reach with the cover in the original position.
*
The wires are not pinched between the cover and the chassis