Summary
The Belar AMM-3A AM Modulation Monitor is an all-solid-state precision AM demodulator which exceeds the US Federal Communications Commission standards for measuring the total modulation characteristics of medium-frequency AM broadcast transmitters.
Features
The detector circuitry of the AMM-3A is non-frequency discriminating, so the unit is suitable for use with shortwave transmitters as well. The AMM-3A employs a unique analog divider circuit which maintains the accuracy of all indications despite changes in carrier level. Simultaneous indications of negative and positive modulation appear on two semi-peak reading meters. Negative and positive modulation peaks are simultaneously indicated on two thumbwheel-programmable peak indicators, as well as individual fixed negative 100% and positive 125% modulation peak indicators. Front-panel pushbuttons select meter indications of relative carrier level and AM noise. The AMM-3A incorporates a carrier-level alarm which indicates when the carrier level falls outside the range required for accurate indications. Also included are an adjustable modulation-level alarm, and a calibration reference to check the accuracy of the readings at any time. An internal jumper can be set to apply the USA NRSC de-emphasis characteristic to the audio outputs.
- Two modulation meters for simultaneous measurement of positive and negative modulation
- Two adjustable peak modulation indicators, thumbwheel programmable from 1-99% negative and 1-199% positive modulation.
- Separate, dedicated 100% negative and 125% positive peak indicators
- All modulation indications independent of carrier level
- Semi-peak reading modulation meters respond accurately to short duration program peaks
- Built-in Carrier Level Limit (Loss) and Modulation Level Alarms with dry relay contact outputs
- Built-in modulation calibration check
- Linear-phase detector filter provides accurate modulation indications without overshoot.
- Switchable NRSC de-emphasis
In addition to the AMM-3A, Belar has a number of analog remote meter panels for use with Belar AM monitors. The MP-7A meter panel is designed for use with the AMM-3A or AMM-3 AM Modulation Monitor. It features the same large backlit meters and all the LED’s as the AMM-3A or AMM-3 for easy remote monitoring.
Technical Specification
Technical Specification
RF Frequency Range:
260 kHz to 50 MHz
RF Sensitivity:
5 Vrms to 10 Vrms
RF Input Impedance:
1000 ohm standard, 50 ohm optional
RF Input:
Rear-panel BNC connector
Positive Modulation Meter Range:
0% to 133%
Negative Modulation Meter Range:
0% to 100%
Accuracy:
±2%
Peak Modulation Indicators:
Negative peak range 1% to 99% in 1% increments
Positive peak range 1% to 199% in 1% increments
Fixed Indicators:
-100%, +125%
Frequency Response:
+0.0 dB, -0.5 dB, 20 Hz to 15 kHz
Envelope Pulse Response:
Overshoot <1%
Modulation Level Alarm:
Adjustable threshold, fixed timeout (-15 seconds)
Carrier Level Meter Range:
0% to 133%
Carrier Limit (Loss) Alarm:
50% & 133% relative level
Audio Monitoring Output:
+20 dBu (4.9 Vrms), 600 ohm active-balanced
Audio Test Output (proof of performance):
2.5 Vrms, rear-panel BNC connector
Auxiliary Detector Output:
5 Vrms
Audio Response:
+0.0 dB, =0.5 dB, 20 Hz to 15 kHz
(detector response -3 dB at 50 kHz)
Distortion:
0.25% maximum at 99% modulation
Signal-to-Noise Ratio:
>_80 dB (de-emphasis out)
AM Noise Level Metering Range:
-40 dB to -70 dB
Remote Outputs:
Adjustable negative and positive peak indicators, -100% and +125% peak modulation indicators; positive and negative remote modulation meters, carrier level reference, modulation level alarm, carrier limit (loss) alarm
Operating Temperature:
0°C to +50°C
Power Consumption:
8 watts, 100-240 V, 50-60 Hz
Dimensions:
5¼”H ´ 19″W ´ 8½” D (EIA rack mount)
Shipping Weight:
11 lbs. (5 kg)
© Copyright 2000 Belar Electronics Laboratory, Inc. All rights reserved.
New in 2015 – 3 Year Factory Warrant to all Belar Products
