RDL ACM-3 – FM Transmitter Amplitude Component Monitor
RDL ACM-3 – FM Transmitter Amplitude Component Monitor is backordered and will ship as soon as it is back in stock.
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RDL ACM-3 – FM Transmitter Amplitude Component Monitor
What is the RDL ACM-3?
The RDL ACM-3 is an amplitude component monitor for FM broadcast transmitters that measures synchronous AM noise, the bandwidth variations that aggravate multipath artifacts in listeners' receivers. RDL describes its ACM technology as the time-proven, industry-accepted method of controlling synchronous AM noise, used by FM stations in every major U.S. market. It gives engineers the accurate AM measurement and continuous monitoring needed to tune any transmitter, new or old, for optimum bandwidth performance.
How does it work?
The ACM-3 takes the filtered transmitter carrier on a BNC input, accepting up to 30 V combined filtered carrier plus AM. Its front-panel display measures synchronous AM from -20 dB to -69 dB, and a BNC oscilloscope jack extends the range from -10 dB to -90 dB at 5 V p-p full scale. Residual noise is more than 95 dB below 100% amplitude modulation, and THD of the recovered AM is below 0.03%. A +4 dBu audio output at 100 Ω source impedance carries the recovered AM, and a DC output provides a level representing significant synchronous AM. With continuous monitoring, stations can maintain clarity, maximize loudness and stereo separation, reduce subcarrier crosstalk and keep signal coverage consistent. The ACM-3 runs from an 18 Vac external supply included for North America and measures 1.7 x 5.8 x 4.1 in. RDL lists Rack-Up mounting options, including the RDL RU-BR1 bracket, RU-SMA1 mounting plate, HR-RU1 adapter kit, MB-1 mounting kit and DRA-35R DIN rail adapter.
What are the key features?
- Synchronous AM measurement — Measures the FM bandwidth variations that cause multipath artifacts.
- Wide measurement range — -20 dB to -69 dB on the front panel and -10 dB to -90 dB on the scope jack.
- Oscilloscope output — BNC scope jack at 5 V p-p for full-scale display.
- Audio and DC outputs — A +4 dBu audio output and a DC level output representing significant synchronous AM.
- Very low residual noise — Better than 95 dB below 100% amplitude modulation.
- Transmitter tuning aid — Supports tuning for loudness, stereo separation and consistent coverage.
- Power supply included — Ships with an 18 Vac external supply for North America.
- Rack-Up mounting — Mounts with RDL Rack-Up series accessories.
Where is it typically used?
- Broadcast studio
Technical Specifications
| Model | ACM-3 |
| Input/Output Connector | BNC |
| Maximum Input Signal | 30 V (combined filtered carrier + AM) |
| Measurement Range | -20 dB to -69 dB (front-panel display), -10 dB to -90 dB (front-panel scope jack) |
| Residual Noise | < 95 dB below 100% amplitude modulation |
| Oscilloscope Jack | BNC 5 V p-p for full-scale display |
| Audio Output | +4 dBu, 100 Ω source impedance |
| THD of recovered AM | < 0.03% |
| DC Output | DC level representing significant synchronous AM |
| Ambient Operating Environment | 32° F to 122° F (0° C to 50° C) |
| Power Requirement | 18 Vac, external supply included (North America) |
| Dimensions | 1.7 in. x 5.8 in. x 4.1 in., (4.1 cm x 15.0 cm x 10.4 cm) |
Frequently Asked Questions
What does the ACM-3 measure?
Synchronous AM noise on an FM transmitter, the bandwidth variations that aggravate multipath artifacts in receivers.
What is its measurement range?
-20 dB to -69 dB on the front-panel display and -10 dB to -90 dB through the oscilloscope jack.
How does it connect to the transmitter?
Through a BNC input accepting up to 30 V combined filtered carrier plus AM.
Is a power supply included?
Yes. An 18 Vac external supply is included for North America.
How is it mounted?
RDL recommends its Rack-Up series mounting options, such as the RU-BR1, RU-SMA1 and HR-RU1.
What warranty does it carry?
This product is covered by a 7-year RDL warranty. For warranty claims, RMAs or support, contact Creation Networks at (888) 230-3661 or sales@creationnetworks.net.
Can Creation Networks help design the system?
Yes. Our team specifies, programs and installs broadcast monitoring systems for commercial projects nationwide. Call (888) 230-3661 for a quote or design review.
At Creation Networks, we do everything we can to create an excellent customer experience. This includes fast shipping and easy returns.
- Most in-stock orders placed Monday-Friday ship within 24-48 hours. General restrictions apply; please see our full shipping policy here.
- We offer a 30-day return policy from the delivery date on many products. Product restrictions apply. Restocking fees for the return of open-box items. Please see our full return policy here for more information.
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