Miniature Transmitter

Manual | Video

The ZMT3 is an ultra small bodypack transmitter filled with Zaxcom’s Emmy Award winning Digital Recording Wireless features like NeverClip™, PowerRoll™ and ZaxNet remote control. This tiny unit will surely open the door to new ways of recording sound for television, sports, theatre and feature films.

The ZMT3 is a wide-band transmitter featuring Zaxcom’s High Density (ZHD) Modulation. The ZMT3 transmitters are also capable of running all existing mono Zaxcom modulations maintaining compatibility with all Zaxcom receivers. ZHD modulation conforms to all currently proposed FCC regulations for spectrally efficient wireless transmission.

Small and durable, it’s housed in a high strength, impact resistant nylon polymer casing with rounded edges, machined metal and rubber gaskets. ZMT runs cool, the combination of the nylon composite case and its power efficiency make the heat transfer practically nonexistent.

The ZMT3 works with ZaxNet, Zaxcom’s 2.4-GHz RF network that distributes remote control commands, timecode and IFB audio. With ZaxNet, one can remotely control transmitter settings such as gain, frequency channel selection, transport controls and output power levels. The ZMT3 also sends a Quality Control audio signal over ZaxNet so when miking someone you don’t have to go to the cart to hear how it sounds, you can use an ERX to listen to the mic right on the spot.

The ZMT3 can be ordered in one of two configurations:
ZMT3.5 – covering blocks 20 through 23 (512-614 MHz)
ZMT3.6 – covering blocks 23 through 26 (596 – 698 MHz)


What is modulation?
Modulation is the way the digital bit stream is transmitted to the receiver. All Zaxcom wireless transmitters have the ability to be set to transmit different modulations types. Each modulation will have different transmission properties for different applications.

What are the available modulations?

  • Stereo – Stereo modulation is used when transmitting a stereo signal from a stereo TRX transmitter.
  • Mono – Mono modulation is used to transmit to legacy receivers and for updating receiver software.
  • XR – XR modulation will have better transmission range than mono modulation.
  • ZHD96 – ZHD96 modulation has a smaller modulation bandwidth and a smaller minimum channel to channel spacing requirement than XR modulation. ZHD96 will perform very well when dealing with reflective surfaces.
  • ZHD48 – ZHD48 modulation has the narrowest modulation bandwidth and the closest minimum channel to channel spacing and the longest transmission latency. ZHD48 will also perform best when dealing with reflective surfaces.

*When used with QRX300 receiver – the minimum spacing is 200 kHz when using all other receivers

What is the modulation bandwidth?
The modulation bandwidth is how much spectrum space the RF signal occupies. The narrower the signal is the more frequencies can fit within a given amount of spectrum space.

What is channel to channel spacing?
If two transmitters are operating too close to each other the signals from the transmitters will interfere with each other. Channel to channel spacing is the minimum number of kilohertz one frequency needs to be set from another frequency to prevent interference. The smaller the spacing, the more frequencies can fit within a given amount of spectrum space.

ZHD is Zaxcom’s High Density modulation mode that will allow up to ten channels of wireless to be operated in just one MHz of spectrum space. ZHD is standard in the ZMT3, TRXLT3, TRXLA3, TRXFB3 and TRX743.

ZMT3 Miniature Transmitter

ZHD Key Features:

  • A single 6 MHz American television channel can contain up to sixty channels of ZHD wireless when used with a QRX300 receiver spaced 100 kHz
  • The wireless signal is only 48 KHz wide and frequencies can be spaced as close as 100 kHz apart
  • RF transmitter power is adjustable up to 100 mW on TRXLA3 & TRX743
  • Incredible transmission distance due to ZHD’s highly efficient modulation
  • Transmitters are available as 3.5 (518 – 614 MHz) and 3.6 (596 – 698 MHz)

TRXLT3, TRXLA3 and TRX743 transmitters are capable of running either ZHD modulation or any existing mono modulations so they maintain compatibility with all Zaxcom receivers. ZHD modulation mode conforms to all currently proposed FCC regulations for spectrally efficient wireless transmission.

ZHD96 modulation works in single or dual mode on all current QRX200 series receivers.
ZHD48 modulation works in single mode only with the QRX300 receiver.

Frequency spacing:

ZHD modulation with QRX300 – 10 frequencies per MHz – 60 per TV channel
ZHD modulation with QRX200, QRX235, RX200, QRX212 – 5 frequencies per MHz – 30 per TV channel
Current XR modulation with QRX200, QRX235, RX200, QRX212 – roughly 2.5 per MHz – 15 per TV channel

Frequency Spectrum Display of ZHD Modulation

Frequency Spectrum Display of ZHD Modulation

Stereo Mono XR ZHD96 ZHD48
Modulation Bandwidth 200 kHz 200 kHz 200 kHz 96 kHz 48 kHz
Minimum Channel to Channel Spacing 400 kHz 400 kHz 400 kHz 300 kHz 100 kHz*
6 MHz TV Channel Capacity 15 15 15 30 60
Latency 3.5ms 3.5ms 6ms 6ms 18ms
Compatibility with 200 Series Receiver 2 Transmitters 2 Transmitters 2 Transmitters 2 Transmitters 1 Transmitter
Compatibility with QRX300 Receiver no no no no 1 Transmitter
Technical Details
RF Modulation: Proprietary Digital Method
ZMT3.5 RF Frequency Range: 512 - 614 MHz
ZMT3.6 RF Frequency Range: 596 - 698 MHz
RF Frequency Step: 100 KHz
RF Bandwidth in ZHD48 Mode: 50 KHz
RF Bandwidth in ZHD96 Mode: 100 KHz
RF Bandwidth in XR Mode: 200 KHz
Channel Separation in ZHD48 Mode: as close as 100 KHz (receiver dependent)
Channel Separation in ZHD96 Mode: as close as 200 KHz
Channel Separation in XR Mode: 400 KHz
Antenna Connector: 50 ½ SSMA Female
Emission Designator: 180 KV2E, 100 KV2E, 50 KV2E
FCC Part: 74.861
Transmitter Audio
Dynamic Range: 128 dB
Distortion: 0.002%
Frequency Response: Mode 0: 20 Hz to 16 kHz / T & M Mode 0.2 Hz to 16 kHz
High Pass Filter: Off or 30 to 220 Hz, Steps: 10 (6 dB Per Octave)
Mic Power: 3.3 VDC
Mic Connector: 3-Pin Micro LEMO
Input Range: -60 to -30 dBu
Mic Impedance: 6.8 k ½
ADC Bit-Depth: 24 Bits
ADC Sampling-Rate: 48 kHz
Timecode Reader / Generator
Timecode output: 3-Pin Micro LEMO
Clock Accuracy: 1.54 PPM (1 Frame Out in 6 Hours)
Timecode Type: SMPTE
Timecode Frame-Rates: 23.98, 24, 25, 29.97NDF, 29.97DF, 30NDF, 30DF
Internal Recording
Media: MicroSD Card (Flash Memory)
File Format: .ZAX / Converts to BWAV or MP3
2.4 GHz ZaxNet Receiver
RF Frequency Range: 2.403 to 2.475 GHz
RF Modulation: Digital Spread Spectrum
RF Frequency Step: 0.001 GHz (1 MHz)
RF Bandwidth: 1 MHz
Channel Separation: 2 MHz
Sensitivity: -96 dBm
Weight: 2.2 oz with Battery
Dimensions (H x W x D): 2.2_ x 1.6_ x .55_
Display: Graphic OLED
Power Output: 25 / 50 / 75 mW Ð Software Selectable
Battery Type: NP-50
Battery Life: Up to 5.5 Hours







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