MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
5
Note: To obtain greatest accuracy, use the minimum possible length of leads and the fewest possible
connectors or adapters. Rather than present readings outside the reliable range as exact
numbers, the MFJ-269 gives a display warning. If (Z>1500) appears on the display, the
impedance is greater than 1500 ohms and outside the reliable instrument range.
2.0 POWER SOURCES
This section describes power supply and battery selection.
+
READ THIS SECTION BEFORE CONNECTING THIS DEVICE TO ANY POWER
SOURCE. IMPROPER CONNECTIONS OR INCORRECT VOLTAGES MAY
CAUSE DAMAGE TO THIS PRODUCT!
2.1 External Power Supply
MFJ has an optional power supply, the MFJ-1315, that satisfies all external supply requirements. We
highly recommend using this supply.
Voltage must be more than 11 volts, and preferably less than 16 volts, when the unit is on and operating.
Maximum “sleep mode” and “OFF” voltage (when the power supply is lightly loaded by this unit) is 18 volts.
The supply must be reasonably well filtered, the case of the MFJ-269 is connected directly to the negative
terminal. The supply must
not
have a grounded positive lead.
The MFJ-269 can be used with external low voltage dc supplies (MFJ-1315 AC adapter recommended).
The
ideal supply voltage is 14.5 volts dc, but the unit will function with voltages between 11 and 18 volts. The
current demand is 150 mA maximum on HF and VHF, and 250 mA maximum on UHF).
WARNING: READ SECTION 2.2 THROUGH 2.4 (BATTERY INSTALLATION
INSTRUCTIONS) BEFORE INSTALLING BATTERIES.
The MFJ-269 has a recessed 2.1 mm power-type receptacle near the RF connectors. This receptacle is labeled
“POWER 12VDC”
.
The outside conductor of the
POWER
receptacle is negative, the center conductor positive.
Inserting a power plug in the “
POWER 12VDC”
receptacle disables internal batteries as a power source.
Internal batteries, although disabled for operating power by inserting a power supply plug, can still be trickle
charged.
WARNING: REVERSE POLARITY OR EXCESSIVE VOLTAGE CAN DAMAGE OR DESTROY
THE MFJ-269. NEVER APPLY MORE THAN 18 VOLTS, NEVER USE AC OR
POSITIVE GROUND SUPPLIES! NEVER ADD OR REMOVE BATTERIES WITH
AN EXTERNAL POWER SUPPLY CONNECTED TO THIS UNIT, OR WITH
THE POWER SWITCH ON.
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