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An Introduction to ZHD Modulation

ZHD is Zaxcom’s new High Density modulation mode that will allow up to10 channels of wireless to be operated in just one MHz of spectrum space. ZHD will be standard in the TRXLT3, TRXLA3 and TRX743 that will begin shipping worldwide June 2016.

TRXLA3 Transmitter

TRXLA3 Transmitter

ZHD Key Features:

  • A single 6 MHz American television channel can contain up to sixty channels of ZHD wireless
  • The wireless signal is only 50 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.

Currently the ZHD modulation will work in single mode on all current QRX200 series receivers, but it will not work in dual mode. There will be a dedicated ZHD receiver in the future.

Frequency spacing:

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

Frequency Spectrum Display of ZHD Modulation

Frequency Spectrum Display of ZHD Modulation


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