MFJ-249C Instruction Manual
HF/VHF SWR Analyzer
2
1.2 Typical
Uses
The MFJ-249C may be used to adjust, test, or measure the following:
Antennas:
........................................SWR, impedance, resistance, resonant frequency, and bandwidth
Antenna tuners:
.............................SWR, bandwidth, frequency
Amplifiers:
.......................................Input and output matching networks
Coaxial transmission lines:
........SWR, velocity factor, loss, resonant frequency
Matching or tuning stubs:
...........SWR, resonant frequency, bandwidth
Traps:
................................................Resonant frequency and approximate Q
Tuned Circuits:
...............................Resonant frequency
Small capacitors:
...........................Value
RF chokes and inductors:
...........Self resonant frequency, series resonance, and value
Transmitters and oscillators:
.....Frequency
The MFJ-249C as a non-precision signal source:
VFO output is leveled at approximately 3-Vpp, or around 20 milliwatts into a 50-ohm load. This signal is relatively
pure with harmonics better than -25 dBc (dB below the fundamental-frequency carrier). The internal source
impedance (Zo) is 50 ohms.
A more complete description of the MFJ-249C's features along with proper measurement methods can be found by
reading sections covering the particular measurement you wish to make. Consult the table of contents for various
applications.
1.3 Frequency
Range
The MFJ-249C covers 0.53* to 230 MHz without frequency gaps using a precision reduction-drive VFO tuning
capacitor and two band switches. Bands of coverage are:
Main Switch:
155-230 MHz
113-155 MHz
67-113 MHz
28-67 MHz
11-28 MHz
Lower Range
Lower Range Switch:
4.7-11 MHz
2.1-4.7 MHz 1.0-2.1
MHz
0.53-1.0 MHz*
*Note that
LF coverage may be shifted from 0.53-1.0 MHz down to 0.47 - 0.94 MHz
for 600-Meter and
maritime frequency coverage. To retune, remove the cabinet and use a small hex wand (2-mm) to adjust
inductor L12 while watching the LCD frequency display.
2.0 POWER
SOURCES
Please read this entire section before connecting your analyzer to any power source. Improper
connections or incorrect voltages may cause permanent damage to your analyzer!
2.1
External Power Supply
MFJ offers an optional power supply, the MFJ-1312D, that satisfies all external supply requirements. We
strongly recommend using this supply.
If you use a different power source, note that the voltage output must be
greater than 11 volts and less than 16 volts
when the analyzer is powered on and running (loaded power source).
The
maximum voltage
in
Sleep Mode
(unloaded power source) should
never exceed 18 volts
.
AC adapters must be
well filtered and the plug must have a grounded sleeve and positive center lead. The ideal voltage-source
specification is 13.8 VDC at 150 mA.
Confirm your supply can deliver this output level safely without overheating
or introducing excessive AC ripple.
