AMM-SD1 Series - Amplitude Modulation Monitors

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Accurate, professional quality precision instruments for all types of AM transmitters and Broadcast Stations.

Radio Engineering Associates is pleased to offer our AMM-SD1 (Software Display) series of AM Modulation Monitors. These devices represent a breakthrough in accurate, easy to use and highly cost effective instrumentation for measuring and monitoring Amplitude Modulation transmitters and signals.

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How it works The AMM-SD1 Modulation Monitor uses with a USB connected, microprocessor based hardware interface and RF demodulator. The RF demodulator is generally connected to the transmitter (or transmission line). The microprocessor interface connects to the display computer using a USB cable.

The Modulation Monitor Software is installed and run on the display computer, and this software displays the percentage of modulation and modulation envelope in a series of user-selectable windows. A screen shot of the Modulation Monitor software is shown above.

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A few Highlights of the AMM-SD1 Modulation Monitor

  • Peak reading
    The AMM-SD1 shows your actual, peak modulation percentage at all times.

    The monitor features a number of user-selectable, high resolution displays including positive and negative Analog meters, positive and negative bar-graph meters, and an oscilloscope-type display. The analog and bar-graph displays feature peak-hold. The peak-hold shows you the most recent, high positive and negative peak level.

  • Instant Response
    There is no latency. The high performance software display of the AMM-SD1 responds instantly.

  • Meter Displays (All displays are user selectable)
    The Analog meter display emulates a classic, direct illumination, large modulation meter system which was popular starting in the 1940s, and continuing through the 1960s.

    The Bar-Graph meter features the unique R.E.A. positive-peaks-over-negative-peaks display which, in addition to showing the modulation percentage, gives a clear visual representation of the modulation Asymmetry (positive peaks as compared to negative peaks) of the modulated signal, in real time.

  • Peak Flashers Adjustable negative and positive peak flashers warn you when the modulation is getting too high.

  • Extended Measurement Range
    Unlike most other commercial modulation monitors, the AMM-SD1 will accurately display positive peaks up to 160%, typical for many good-quality transmitters.

  • *** Remote Access ***
    The AMM-SD1 allows the station engineer to view the modulation (and optionally listen to the audio) using the Internet or a LAN from a remote location. The Modulation Monitor software running on the local (connected to the transmitter) computer allows other computers running the Modulation Monitor software to connect, and view (and optionally hear) the modulation in real time.

    Using the Modulation Monitor, it is possible for a station engineer to remotely monitor several remote sites and/or transmitters at the same time, all from a single computer.

The AMM-SD1 is used in many applications including:

  • Standard AM Broadcast Stations
  • Short-Wave Broadcast Facilities (particularly multi-transmitter facilities)
  • Amateur Radio Stations using AM (not usable with SSB)
  • Citizen's Band Radio (CB)
  • Carrier-Current (campus) Broadcasting
  • Informational (travel information, traffic reporting, etc.) stations
  • Radio Repair Shops and Facilities
  • Educational Institutions


  • Accurate, peak reading measurements of modulation.
  • Separate positive and negative peak meters (100% Negative, 160% Positive) with peak-hold
  • Instant display of modulation asymmetry.
  • Adjustable threshold negative and positive peak flashers
  • High fidelity audio output, suitable for driving external audio equipment.
  • Remotely located RF pickup/detector units keep the RF at the transmitter or antenna feedline, where it belongs!
  • Need to build your own RF pickup/detector unit? RF pickup/detector units are very easy to construct, allowing pickup units to be built into transmitters, if required
  • 2.5% accuracy!
  • Covers the entire MW and HF range from 500kHz to 30mHz
  • Coverage can be extended to virtually any frequency or power level by using a custom detector. You may build your own detector, or we can supply a custom unit. Contact us with your needs.
  • High Impedance RF input - uses a negligible amount of RF power, allowing the monitor to be used with low power transmitters without signal loss
  • Built in the United States of America!
The AMM-SD1 is an exceptional value and has key features absent from other modulation monitors costing many times more making the AMM-SD1 the highest value, lowest cost, accurate peak reading monitor available!

Simple to Install and Connect to a Wide Variety of Equipment

Connecting the AMM-SD1 to your transmitter is simple. The monitor includes one standard RF pickup unit. 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.

  • Other connection methods Contact us ! We can advise you of the best connection for your purpose.

Shown to the left is a typical in-line connection. In this example, the rf pickup unit is 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-SD1 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-SD1 features a wide range, high impedance audio output. This output is suitable for driving an audio monitoring amplifier, headphone amplifier or other similar audio system. Note: This output is not designed to drive headphones directly.

Computer Hardware and Software Requirements

The Software download page is here

Software Requirements:

  • Microsoft Windows XP (SP3 or better), Windows 7 (SP1 or better), Windows 8, Windows 10, Windows 11 (should work with all versions of Windows - NT and later)
  • High speed Internet connection only used for downloading the installation software (not required after the software has been downloaded, except for updates). Note: A network connection of at least 768kbps is required for remote operation.
Computer Hardware Requirements:
  • Intel Pentium 4, 1.2gHz or better
  • 500mb or more RAM recommended
  • Good quality VGA or better video adapter
  • 1 free USB "A" socket

Pricing and Availability: IN STOCK !

Price: $234.95 (US Dollars)

Price Includes:

  • Model AMM-SD1 Monitor with a USB interface, and the Modulation Monitor Software License (software download from our software distribution server. CD Media is also available). The Software can be installed on multiple computers for remote operation.
  • 1 RF pickup unit with SO-239 connector. Note: Specify desired power level for the RF Pickup Unit when ordering. The following standard power level RF pickup units are available. Contact us if you need another power level:
    • Direct Connect to a standard AM Broadcast Transmitter modulation monitor RF output (12V Max.).
    • 200 - 1000 Watts (carrier)
    • 50 - 500 Watts (carrier)
    • 30 - 300 Watts (carrier)
    • 10 - 100 Watts (carrier)
    • 3 - 30 Watts (carrier)
    • 1 - 10 Watts (carrier)
    • Other (contact us!)
  • Interconnecting cable to connect RF pickup unit to monitor (1/8 inch shielded dual cable).
  • User Manual

Options and Add-Ons

  • Additional standard RF Pickup Units - $50.00
  • Tee Adapters and Male-to-Male Adapters for connecting RF Pickups in-line
  • Physical media containing the software. Note: Normally the software is downloaded from the R.E.A. software download page. This ensures you have the latest version of the software.

Purchasing the AMM-SD1

How to Order:

Satisfaction Guarantee!!

If you are not completely satisfied with your purchase, you may return it within 15 days of receipt (in new condition in original packing) for a full refund. Shipping costs are not refundable.

Contact Us:

Radio Engineering Associates Inc.
75 Mirror Lake Dr
Mirror Lake, NH 03853
Phone: 978-597-0010