MFJ-224 Instruction Manual
2-Meter FM Analyzer
4
Orientation--Hooking Up Your Meter
To become familiar with the various features and functions of your MFJ-224, connect it
up as shown below (if you lack an oscilloscope, omit that portion of the orientation).
1. Headphones:
You'll need a pair of low-impedance headphones outfitted with a 3.5
mm (1/8") plug. Without phones, you will be unable to identify signals and tune them in
properly. The headphone circuit is configured to work with either stereo or monaural
plugs and wiring, but a pair of good-quality stereo phones work best. Headphone audio
level is pre-set to a low-but-comfortable listening level.
2. Antenna:
The MFJ-224 accepts any 50
Ω
source outfitted with a UHF connector.
Avoid directly-connecting RF levels exceeding -20 dBm (.03 volts) to the meter. To
sample stronger sources, use a pick-up probe or resistive attenuator. For the purpose of
this orientation, connect a 2-Meter station antenna to monitor off-air signals.
IMPORTANT NOTE: Your MFJ-224 is a sensitive instrument. To avoid damage,
never connect a transmitter or powerful RF oscillator directly to the antenna jack.
3. Oscilloscope:
Connecting a scope to the MFJ-224 enhances its value as a deviation
meter and audio analyzer. Since only audio frequencies are monitored, any general-
purpose scope will have sufficient frequency response. However, a well-calibrated unit
will yield more accurate deviation readings. Connect your meter to the scope's vertical-
amplifier input using shielded cable. To begin, set the sweep for .5 mS and vertical gain
for 0.2 volts per division. A 1-kHz test-tone modulating a FM transmitter to 5-kHz of
deviation normally produces a sine-wave output of about 1.0 volts p-p.
0.2V
Vert
Scope Phones
Antenna
2-Meter Antenna
Oscilloscope
Headphones
MFJ-224
You are now ready to explore the basic features and functions of the MFJ-224.