MFJ MFJ-224 Instruction Manual

2-Meter FM Analyzer 1 Introduction Congratulations on purchasing the MFJ-224 2-Meter FM Analyzer. With this versatile handheld instrument, you can tune in any signal between 143.5 and 148.5 MHz to monitor field strength in dBm and FM-deviation in kHz. Accurate tuning is made simple, thanks to the built-in discriminator-meter function. Battery status is also displayed. In addition to metered functions, the MFJ-224 lets you vis ...

2-Meter FM Analyzer 2 What Your Meter Can Do The MFJ-224 performs countless jobs around the shop or radio shack. Here are some uses we think you'll appreciate: •••• Evaluate Antenna Performance: Measure key yagi specifications such as gain over a dipole (dBd), beamwidth (-3dB points), front-to-back ratio, and sidelobe suppression. You can compare antennas to see which works best, and check the real-world performance of ...

2-Meter FM Analyzer 3 How Your Meter Works A Motorola FM-receiver IC with logarithmic RSSI metering circuitry measures signal strength over a 60-dB dynamic range. This allows input levels from -100 dBm to -40 dBm to be displayed on a linear meter scale with 1-dB resolution. In addition to providing accurate RSSI, the IC features a built-in tunable oscillator--plus outputs to drive the FM-deviation detector, headphone monitor ci ...

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 cir ...

2-Meter FM Analyzer 5 Orientation--Learning To Use Your Meter 1. Power On: To power-up your unit, depress the power switch. The green pilot LED should illuminate. 2. Battery Status: To check battery condition, turn the meter selector switch to battery and note the indication. The meter should swing into the good zone of the scale. 3. Headphone Monitor Switch: To monitor signals, plug in headphones and depress the monitor ...

2-Meter FM Analyzer 6 for the meter to read below -100 dBm with no signal present. Check the repeater signals in your area and note the level differences between them in dB! ...

2-Meter FM Analyzer 7 7. Deviation Function: Use the deviation function to check transmitter modulation. The 0-7 kHz scale on the meter is accurate only when a continuous audio or packet calibration tone is applied to the transmitter under test. However, you can get a pretty good idea who's over-deviating and who's not by watching meter movement on normal speech. For a better look at deviation, turn on your oscilloscope. Thi ...

2-Meter FM Analyzer 8 3. Comparing Antenna Performance: The Signal display is useful for comparing two or more antennas for best performance. In most cases, a local repeater may be used as a signal source. These results can be extremely accurate, but only if steps are taken to prevent error. Here is a list of tips for getting good results: [ ] Position each antenna at the same exact location and height (one at a time). [ ...

2-Meter FM Analyzer 9 Sidelobe Suppression: Sidelobes are "peaks" in antenna response that occur off the side of a directional antenna. A well-designed yagi will have a clean well-defined pattern with only a few weak sidelobes. However, a poorly-designed yagi may have several strong peaks off to the side. If your yagi has a sidelobe problem, you can spot it easily on the RSSI display as you rotate the antenna. However--bewar ...

2-Meter FM Analyzer 10 Measuring Deviation Deviation is the amount of carrier-shift used by FM transmitters to convey speech or data. For more information about how frequency modulation works, consult a current edition of The ARRL Handbook for Radio Amateurs. The FM reference will provide a useful theoretical background for this popular mode. Controlling deviation is important. Too much of it will cause interference on adjacent ...

2-Meter FM Analyzer 11 3. Deviation Readout with an Oscilloscope: Checking deviation with a scope provides an instantaneous peak display of modulation level. This means you can look at speech waveforms and estimate deviation with reasonable accuracy--something not possible using the meter scale. Also, low-level signals such a PL-tones (CTCSS) are set easily using the scope display. Finally, audio problems such as overload di ...

2-Meter FM Analyzer 12 Limitations The MFJ-224 is a highly-affordable handheld tester that will help you perform many functions that would otherwise require a sophisticated FM service monitor. However, please keep in mind that it is not a direct replacement for a $5000 commercial instrument! Here are some of the unit's natural limitations--and some useful tips to help you work around them: 1. The VFO is LC-tuned (not synthesized ...

2-Meter FM Analyzer 13 Field Service Guide The MFJ-224 has several serviceable calibration adjustments. If you lack the necessary equipment or expertise to service sensitive VHF communications equipment, please do not attempt these adjustments! Instead, contact a qualified 2-way service technician in your area for assistance or return your unit to the factory for service. To service the unit, remove the screws from the side of ...