BELAR AMM-4 AUTOMATIC AM FREQUENCY MONITOR
The Belar AMM-4 is a digital AM frequency monitor designed especially for automatic broadcast transmitter monitoring. The counter will accurately monitor any frequency from 10 kHz to 50 MHz. A large 3½ digit LED display provides a range of ±1999 Hz deviation from the assigned channel. A front panel LED indicator warns of low RF level or loss of carrier; an optional relay contact can be provided. The monitor also provides two off-frequency alarms which are inhibited so that three successive errors are required to signal an alarm. This prevents false off-frequency conditions. For example, of the carrier frequency exceeds ±10 Hz, a front panel LED indicator is immediately actibated into a flashing state. This warns of an impending off-frequency condition. After three successive counts in this condition, the monitor will actibate an optional relay contact for remote alarms. It also changes the front panel indicator to a continuous ON state. If the frequency exceeds ±20 Hz for three sucessive counts, then the second front panel indicator is activated as well as an optional relay contact.
Another feature of the AMM-4 is the invalid count alarm. If this condition arises due to low RF level or a malfunction in the counter, the frequenct alarms are held in their OFF condition; however, a front panel LED indicator and optional relay contact are provided to warn of an invalid count.
If the counter is driven by a modulated source, a count inhibit input is provided. This input is controlled by the 100% negative output of a modulation monitor; thus if the modulation level exceeds 99% negative, then the display and alarms would be held at the state they were in prior to the overmodulation fault.
Relay contact outputs (described above) are available as options. A switchable 1 MHz input/output connector is provided for frequency comparison.
Frequency Range 10 kHz to 50 MHz Display Large 3½ digit LED Display Range ±1999 Hz Sensitivity 100 mV, Unmodulated 2 Vrms, 99% modulation Gate Time 2 seconds Resolution 0.5 Hz Time Base (internal) 6 MHz Stability ±1 x 10^-6 per year Time Base (External) 1 MHz TTL compatible level 10 Hz alarm Front panel LED, inhibited for three successive errors 20 Hz alarm Front panel LED, inhibited for three successive errors RF alarm Front panel LED, warns of low RF level or carrier fail condition Invalid Count Alarm prevents false counts due to low RF level or problem in counter Count Inhibit Input External contact required capable of sinking 2mA Level Alarms 3 LED Indicators Dimensions 1.75"H x 10.5"D x 19"W (EIA Rack Mount) Power Requirements 115/230 VAC, 50/60 Hz© Copyright 2000 Belar Electronics Laboratory, Inc. All rights reserved. Specifications subject to change without prior notice.
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