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AMT3000 and AMT5000 AM Radio Broadcast Transmitter Kits

Setting the Quality Standard for High Quality, Low Power, FCC Part 15 Transmitters



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Why Choose the AMT5000?

If your application falls in one of the following categories, the AMT5000 is your best choice:

  • low-power broadcasting
  • information station for your retail business
  • "parking lot" information
  • real estate advertising near a property for sale
  • full coverage over a large personal property


FCC rules limit the power input to the final RF stage to 100 mW. High efficiency enables more of that precious power to be transferred to your antenna. The AMT5000 combines super-high efficiency class E mode RF generation with an efficiency-optimized toroid loading coil for nearly the best efficiency possible. The toroid loading coil is designed for best efficiency in the frequency range of 1350 kHz to 1710 kHz. At the top end of the AM broadcast band, this coincides with best 3 meter vertical antenna efficiency.

Read "About Transmitting Range and Antennas" on this page for details about range for indoor and outdoor installations.

Built-In Audio Processing

Uses the same, proven compression and limiting circuit as the AMT3000, ensuring a constant high modulation level independent of the variations in audio source level.

Consumer and Pro Audio Inputs

You can choose either the Consumer Audio RCA jacks or the Pro Audio screw-terminal inputs depending on your needs. If your transmitter will be located outdoors, and possibly a long distance from the audio source, you should consider using the Pro Audio input. This input allows long distance audio feeds via balanced twisted-pair wires, which reject noise and hum. The Pro Audio input has protection against static electricity buildup and static surges on the audio wires.

130% Positive Peak Modulation Range

This capability simply refers to the available modulation "headroom". Normally, distortion will rise rapidly as you transition above 100% modulation. However, some commercial audio processing devices, such as the Inovonics 222, have asymmetrical peak limiting controls allowing you to set positive and negative peak limiting levels separately. You can connect asymmetrical processors and gain their full advantage.

For educational purposes, you can use the AMT5000 as a teaching aid or classroom demonstrator for instruction related to Class E mode RF principles.


  • Designed to equal or exceed the range and audio quality of all other FCC Part 15 AM transmitters currently being sold at any price.
  • Fully compliant with all applicable FCC part 15 rules for operation in the AM broadcast band without licensing.
  • The RF output stage uses a low-on-resistance power MOSFET transistor operating in the Class E switching mode at 98% drain efficiency when tuned per instructions. Only 2% of the available 100mW input power is dissipated in the transistor. Power input to the final RF stage is adjustable to comply with the 100mW limit mandated by the FCC for license-free Part 15 AM transmitters. You can reduce the input power below 100mW to prevent overloading nearby receivers when using the transmitter indoors.
  • Various antenna options: a 118" length of wire is included for indoor use. For outdoor installations, you can mount the transmitter in a weatherproof box and connect to a 102" CB antenna or 118" copper or aluminum pipe antenna. No external loading coil or length adjustment is required.
  • A large custom toroid coil tunes the antenna in the 1350 kHz to 1700 kHz frequency range. The toroid has an iron-powder core selected for maximum efficiency in this frequency range.
  • Crystal controlled frequency synthesizer covers entire AM broadcast band in 9 kHz or 10 kHz steps, depending on order option.
  • Professional quality audio compression and limiting maintains 100% modulation regardless of audio input level. Adjustable 1:1 db to 5:1 db compression ratio. Audio levels above the adjustable limit level are compressed at 15:1 db ratio.
  • Audio response at the final modulation transistor output is 20Hz to 20 kHz ±1 dB.
  • Modulated RF 3-dB Response: 20 Hz - 16.5 kHz with 20-30 ohm RF ground (typical for a reasonably good RF ground).


  • Consumer Audio and Pro Audio inputs: Two RCA input jacks are mixed to convert a Consumer Audio stereo source to mono or to mix two separate Consumer Audio mono sources. Screw-terminal inputs for Pro Audio +, -, ground.
  • Jumper selectable flat or treble-boost audio curves. Treble boost pre-emphasis will compensate for the typically poor high frequency audio response of most AM radios.
  • Two voltage regulators and an on-board, RF-bypassed, bridge rectifier assure clean, hum-free power. The standard 120 VAC to 12 VAC wall adapter is included.
  • Jumper options for operating from unregulated 12 VAC, 12-15 VDC or 12 VDC battery power sources.
  • Very low 2 Watt AC power consumption for worry-free continuous operation.
  • Highest quality double-sided printed circuit board has top and bottom solder masks and a top silk screen legend to clearly identify component locations.
  • The three surface-mount components are pre-soldered on the board.
  • Designed for ease of assembly. All components mount on the printed circuit board. No time consuming discrete wiring required.
  • High-strength ABS plastic enclosure. Front and rear panels are pre-drilled and screen printed.
  • The instruction manual guides you, step-by-step, through the assembly process to reduce the chance of errors during kit assembly.
  • Kit is educational and fun to build.


About Transmitting Range and Antennas


When using your AMT5000 indoors with the included antenna wire, expect a very strong signal throughout the building (you may need to reduce the input power adjustment below 100mW to prevent receiver overload).

The range outside the building depends on two major factors: (1) the shielding effect of the building siding and (2) the amount of your signal that is radiated out over the power lines feeding your building.

Aluminum siding and stucco-over-wire-mesh are two siding methods that shield the signal the most. Power line radiation is quite unpredictable. So, you can expect anywhere from 50 ft. to several thousand feet range from inside a building. That information isn't very helpful, but reality doesn't make a useful range prediction possible.


You can maximize your range, and make it independent of your building and power-line radiation effects, by installing the transmitter outdoors, well clear of surrounding obstacles. Use a 102" stainless-steel CB whip antenna or a copper or aluminum pipe 118" long. A standard 8 ft. long copper-clad electrical ground rod should be driven into the ground at the base of the antenna for lightning protection. Four or more 15 ft. (or longer) radial wires fanning out from the ground rod connection on or buried slightly below ground will greatly improve your range. With such an installation, expect 3/4 to 1 mile range for a fairly strong signal on a car radio. A listenable signal can often be heard in some directions at 2+ miles. High building density and a high local ambient electrical noise level will reduce the range.

The AMT5000 has a jumper option for completely bypassing all internal RF output tuning inductors, including the toroid, for those who would like to experiment with an antenna using a large external air-core loading coil. Such an antenna will require a tapped air core coil and a method for adjusting the antenna length for fine tuning.


Thanks to a great contribution from one of our very inventive customers, here is a PDF file showing how to modify the antenna with a sleeker in-line coil.


Constructing the base-loaded antenna is made a lot easier thanks to Carl Van Orden. He sells the complete tapped coil, wound on a section of 3” white PVC pipe as shown in the plans. This is the most difficult part of the antenna to fabricate. Carl also sells ground radial systems. For more information and prices, click on the following link to see Carl’s page.




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