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AMM-HF1 Amplitude Modulation Monitor
Highly accurate, professional quality precision instrument for all types of AM transmitters and Broadcast Stations.Peak reading, the AMM-HF1 shows your actual modulation percentage at all times. AM is an absolute value, peak based modulation system, and the AMM-HF1 shows you the real peaks. The monitor features separate high resolution (100 LEDs total) positive and negative bar-graph meters, including peak-hold. The peak-hold shows you the most recent, high positive and negative peak level.
Because the LED display of the AMM-HF1 responds instantly to your transmitter's true peak modulation, this modulation monitor is the perfect instrument for measuring and monitoring the modulation of complex, varying audio signals such as voice or music.
This unique positive-over-negative LED display lets you immediately and instantly determine the Asymmetry (positive peaks as compared to negative peaks) of the modulated signal, in real time.
An adjustable negative peak flasher warns you when the negative modulation is getting too high.
Unlike most other commercial modulation monitors, the AMM-HF1 will accurately display positive peaks up to 150%, typical for many good-quality transmitters.
The AMM-HF1 has key features absent from other modulation monitors costing many times more making the AMM-HF1 the highest value, lowest cost, peak reading monitor available!
If you use or operate any equipment using Amplitude Modulation (AM), it is generally necessary (and in many cases, legally required) to monitor your transmitted signal continuously while you are on the air. Constant modulation monitoring will let you know the transmitter is working correctly, and that you are providing sufficient audio to the carrier without overmodulating. Furthermore, you will know immediately that your audio is in the correct phase with respect to your voice, microphone, processing and transmitting equipment. This is vitally important if you want to have a loud, well modulated, distortion-free signal.
Proper monitoring and control of the modulation of your signal:
- Lets you know exactly what kind of signal you're putting out, and that everything is working properly.
- Ensures you will not transmit a distorted signal due to overmodulation ... and ...
- Helps prevent FCC trouble since overmodulation causes spurious emissions and is also a violation of FCC rules in most cases. Knowing when you are overmodulating and making corrective adjustments will keep you legal.
- Allows you to adjust your equipment to put more modulation in the positive (upward) direction, making the signal louder while avoiding distortion.
- Gives you a full-fidelity, off-air audio monitor. You will know what you sound like and how adjustments change the sound.
- Shows carrier shift and other abnormalities that may indicate a problem with the transmitter or adjustment.
- Lets you hear how you actually sound - on the air.
Simple to Install and Connect to a Wide Variety of Equipment
Connecting the AMM-HF1 to your transmitter is simple. The monitor includes one RF pickup unit (up to 5 may be connected). The Pickup Unit is a high impedance device, and consumes very little power (milliwatts in most cases).Note: A standard RF pickup is included with the Modulation Monitor.
- Connecting to a Broadcast Transmitter Most AM Broadcast Transmitters include an RF output for connection to a modulation monitor. Simply connect the RF pickup unit to this output.
- Connecting directly, in line, with the transmitter output This type of connection is typical for non-broadcast equipment such as short wave, amateur, and other similar equipment. The RF pickup unit is connected directly to the transmission line with a T connector. (See picture). Various power level RF pickup units are available.
- Off-Air pickup - no direct connection to the transmitter This is done when a connection to the transmitter is impossible or impractical, such as with Part 15 equipment, or where there is a great distance between the transmitter and the monitor. Use the Optional Radio Engineering Associates broadband, Off-Air RF pickup unit (NOTE: Currently available as a KIT OF PARTS (with board) ONLY!! Assembled units will not be available unitl 15-May-2007.
- Connecting to a local AM receiver This type of connection is very useful when there are many miles between the modulation monitor and the transmitter. A Radio Engineering Associates optional Off-Air RF pickup unit is connected to the IF (Intermediate Frequency) of a local receiver. The receiver acts as a front-end to the RF pickup unit, which then feeds the modulation monitor.
- Other connection methods Contact us ! We can advise you of the best connection for your purpose.
Shown to the left is an rf pickup unit connected to the antenna feedline using a T connector.
You may also build your own RF pickup unit (plans and specifications are included) allowing the AMM-HF1 to be used in a wide variety of environments, and with virtually any AM transmitter of any power level. Radio Engineering Associates will also build custom RF pickup units for you. Contact us with your requirements.
For Off-Air Monitoring, the AMM-HF1 features 2 audio outputs, one on
the back of the unit (1/8 inch standard mini phone jack) and one on the front,
a 1/4 inch standard headphone jack.