How ZHD Modulation Redefines Wireless Audio
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.
| 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 |
*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.
What is ZHD Modulation?
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 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, ZMT3, TRXFB3 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
