LECTROSONICS HMBLOCK21 UHF Plug-On Transmitter Block 21 - 537.6-563.1 MegaHertz
The Lectrosonics HM Digital UHF Wireless Plug-On Mic Transmitter (Block 21 Frequency) features a DSP-based design that allows the transmitter to operate in its native Digital Hybrid Wireless mode, Lectrosonics 200 Series, 100 Series, IFB product groups, plus two modes for compatibility with analog receivers from other manufacturers. A unique multi-voltage phantom power feature allows the transmitter to be used with virtually any microphone, including high-current condenser types, expanding its usefulness in high-end applications such as motion picture production.
The transmitter provides 256 frequencies in standard frequency blocks, selected with two rotary switches on the side of the housing. The input amplifier uses an ultralow noise op-amp for quiet operation. It is gain controlled with a wide range dual envelope limiter, providing over30 dB of headroom above full modulation. A 24-bit A-D converter digitizes the audio, then filters supersonic noise above 21 kHz. The resulting signal is encoded with a proprietary algorithm to produce an analog data signal for RF transmission. The underlying RF link is an optimized FM system with +/-75 kHz wide deviation for a high signal to noise ratio.
The antenna is formed between the lower housing of the transmitter and the attached system. It functions as a dipole radiator when attached to a hand-held microphone and somewhat like a ground plane antenna when connected into a mixer. The conical shaped collar on the input coupler is made of DuPont Delrin to improve the ERP of the antenna in the uppermost frequency blocks.
