Digital Transmitter
Rio Rancho, NM
3
Introduction
The DCHT, DCHT/E01 transmitter is designed to work
with a companion receiver (such as the Lectrosonics
DCHR or M2R, part of digital camera hop systems) as
an audio relay between an audio production bag or cart
and a camera or other audio device. The 6
-
pin input
jack accepts two mic or line level analog signals or
AES digital signals from external sources with a variety
of adapter cables. Analog inputs can be linked for the
same gain when used with a stereo source, or operate
independently with individual settings.
This fourth generation digital design features specially
developed, high efficiency digital circuitry for extended
operating time on two AA batteries. The transmitter can
tune in 25 kHz steps across the UHF television band
from 470.100 to 607.950 MHz (E01 frequency range
is 470.100 to 614.375 MHz), with a selectable output
power of 10, 25 or 50 mW.
Studio quality audio performance is assured by high
quality components in the preamp, wide range input
gain adjustment and DSP-controlled limiting for analog
sources, and settings are included for any lavaliere
microphone, dynamic microphones, line level inputs,
and AES digital inputs. Input gain is adjustable over a
51 dB range in 1 dB steps to allow a precise match to
the input signal level, to maximize dynamic range and
signal to noise ratio.
A separate switch is provided on the top panel that can
be configured as mute, power or bypassed.
The housing is constructed of solid machined alumi-
num for lasting ruggedness. The exterior is finished
with an ultra hard, dark electroless nickel finish called
ebENi
.
Firmware updates are made through a side panel
microB USB port.
Canada ISED Notice
This device operates on a no-protection, no-interference basis. Should the user seek to obtain
protection from other radio services operating in the same TV bands, a radio licence is required.
For further details, consult Innovation, Science and Economic Development Canada’s document
Client Procedures Circular CPC-2-1-28,
Voluntary Licensing of Licence-Exempt_Low-Power
Radio Apparatus in the TV bands.
General Technical
Description
DSP-controlled Input Limiter
For analog sources, the transmitter employs a DSP-con-
trolled analog audio limiter prior to the analog-to-digital
converter. The limiter has a range greater than 30 dB for
excellent overload protection. A dual release envelope
makes the limiter acoustically transparent while maintain-
ing low distortion. It can be thought of as two limiters
in series, connected as a fast attack and release limiter
followed by a slow attack and release limiter. The limiter
recovers quickly from brief transients, so that its ac-
tion is hidden from the listener, but recovers slowly from
sustained high levels to keep audio distortion low and
preserve short term dynamic changes in the audio level.
Encryption
When transmitting audio, there are situations where
privacy is essential, such as during professional sport-
ing events, in court rooms or private meetings. For
instances where your audio transmission needs to be
kept secure, without sacrificing audio quality, Lectroson-
ics implements AES256 encryption in our digital wireless
microphone systems. High entropy encryption keys are
first created by
one of the units in the system
. The key
is then synced with another encryption-capable unit, via
the IR port. The audio will be encrypted and can only be
decoded if both the transmitter and receiver have the
matching encryption key. If you are trying to transmit an
audio signal and keys do not match, all that will be heard
is silence.
