DISCONTINUED Delta Electronics ASM-1 Modulation Monitor

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Delta ASM-1


ASM-1 Modulation Monitor

The ASM-1 Modulation Monitor helps maintain and ensure AM broadcast system performance. The Monitor incorporates a high performance C-QUAM decoder to demodulate the RF sample. The Monitor provides all the demodulated signals necessary for annual proof of performance when used with standard AM proof equipment.


The signals available on the rear panel of the Monitor include L+R, L-R, Envelope Detector Output, and Left and Right audio (both balanced and unbalanced). The 25 Hz pilot tone is also available.

Available through front panel meters are: positive and negative L+R, L-R, L and R modulation levels. Peak flashers indicate -100%, +125%, L-R Limit, and negative limit modulation conditions.

Two thumbwheel controlled peak flashers can be set to flash at any level of modulation. The modulation meters and the thumbwheel controlled peak flashers are accessible through rear panel connectors for remote indication.

Technical Specification

Technical Specification

RF Input:

Frequency crystal controlled

Input level
1 volt to 10 volts RMS

50 ohms

Modulation Meters:

Meter range:
0 to 140%, -20 dB to +2 dB

Attenuator range:
0 to -50 dB in -10 dB steps
Accuracy at 100% modulation 400 Hz: ±2%
Meters switchable to + or – L, R, (L + R), (L – R)

Peak Modulation Indicators:

(L + R) Group:

-100% indicator internally set to flash when modulation exceeds -99%
+125% indicator internally set to flash when modulation exceeds +124%
Peak indicator adjustable via thumbwheel switches from 30% to 150%
Modulation indicators selectable via pushbutton switches + or –

(L – R) Group:
Negative limit set internally to flash at 1.46 radians or 83.67º
(L – R) limit set internally to flash when phase modulation exceeds 99%
Peak flasher adjustable via thumbwheel switches for 30% to 125%

Output BNC Connectors on Rear:
Remote Flashers (L + R), (L – R)
Remote Meters (L + R), (L – R)
Left Audio 600 Ohms balanced and unbalanced
Right Audio 600 Ohms balanced and unbalanced
(L + R), (L – R), and 25 Hz Pilot Tone

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