Lectrosonics HMa (A1: 470.100 - 537.575 MHz, BLOCKS 470, 19, 20)

Phantom power is selectable at 5, 15 and 48 volts, or can be turned off for use with dynamic micro-phones and line level signal sources.

The design includes a wide tuning range of up to 76 MHz, with tuning steps in increments of 100 kHz or 25 kHz for up to 3072 frequencies. The tuning range covers three standard 25.6 MHz Lectrosonics frequency bands. Each of the standard bands includes 256 different pilot tone frequencies for compatibility with all Digital Hybrid Wireless receivers.

DSP compatibility modes are also included to work with legacy Lectrosonics analog wireless microphone receiv- ers and IFB receivers, as well as some receivers from other manufacturers. The transmitter is powered by two AA batteries, with status indicated by a multi-color LED. A USB port is pro- vided for firmware updates. An IR (infrared) port is also included to simplify setup with IR enabled receivers.

The input amplifier uses an ultra low noise op-amp for quiet operation. It is gain controlled with a wide range dual envelope limiter, providing over 30 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 algo- rithm to produce an analog data signal for RF transmis- sion. The underlying RF link is an optimized FM system with +/-75 kHz wide deviation for a high signal to noise ratio.

The audio performance of the overall hybrid system is de- picted in the graph below. Distortion in the overall system is extremely low over the entire audio bandwidth.

The antenna is formed between the machined aluminum housing of the transmitter and the attached microphone or cable. It functions as a dipole radiator when attached to a hand-held microphone and somewhat like a ground plane antenna when connected with a cable or plugged directly into a mixer. The conical shaped collar on the input coupler is made of DuPontTM Delrin to improve the ERP of the antenna in the uppermost frequency bands.

Digital Hybrid Wireless is a revolutionary design that combines digital audio with an analog FM radio link to provide outstanding audio quality and the ex- emplary RF performance of the finest analog wireless systems. The design overcomes channel noise in a dramatically new way, digitally encoding the audio in the transmit- ter and decoding it in the receiver, yet still sending the encoded information via an analog FM wireless link. This proprietary algorithm is not a digital implementa- tion of an analog compandor. Instead, it is a tech- nique which can be accomplished only in the digital domain. The process eliminates compandor artifacts, expand- ing the applications to include test and measurement of acoustic spaces.

The battery compartment door is hinged to the housing and remains attached to the transmitter when opened. It securely latches in place and applies pressure to the batteries when closed. The two AA batteries are con- nected in series through a conductive plate on the door. Setup and adjustments are made with the control panel membrane switches and LCD. The transmitter can be powered up without the transmitter output enabled to allow frequency adjustments without causing interference to other wireless systems nearby. The switches can also be bypassed to prevent accidental changes.

Dual color LEDs indicate audio input level and the power LED changes color under low battery conditions.

• Accepts microphone or line level signals

• Selectable 5, 15, 48 volt phantom power

• 76 MHz tuning range in 100 kHz or 25 kHz steps for up to 3072 frequencies

• Selectable 50/100 mW output power

• Adjustable low frequency roll-off

• Powered by two AA batteries

• USB port for firmware updates

• IR (infrared) port for fast setup

• Solid machined aluminum housing

OPERATING FREQUENCIES:

Band A1 470.100 - 537.575

FREQUENCY SELECTION STEPS:

Selectable; 100 kHz or 25 kHz

RF POWER OUTPUT:

Selectable 50/100 mW

PILOT TONE:

25 to 32 kHz; 5 kHz deviation (in the Digital Hybrid mode)

FREQUENCY STABILITY:

± 0.002%

DEVIATION:

± 75 kHz (max in Digital Hybrid mode)

SPURIOUS RADIATION:

60 dB below carrier

EQUIVALENT INPUT NOISE:

-125 dBV (A-weighted)

INPUT LEVEL:

Nominal 2 mV to 300 mV, before limiting. Greater than 1V maximum, with limiting.

INPUT IMPEDANCE:

300 Ohms

INPUT LIMITER:

Dual envelope "soft" limiter; greater than 30 dB range

GAIN CONTROL RANGE:

55 dB; panel mounted membrane switches

MODULATION INDICATORS:

Dual bi-color LEDs indicate modulation of -20, -10, 0, +10 dB referenced to full modulation

FREQUENCY RESPONSE:

35 Hz to 20 kHz (+/-1dB);

LOW FREQUENCY ROLL-OFF:

Adjustable for -3dB @30, 50, 70 Hz)

THD:

0.2% (typ. 100 Hz to 20 kHz)

AUDIO INPUT JACK:

Standard 3-pin XLR (female)

PHANTOM POWER:

5V @ 18 mA max., 15V @ 15 mA max. and 48 V @ 4 mA max., plus "OFF"

USB PORT:

Used for firmware updates

IR (INFRAFED) PORT:

For quick setup by transferring settings from an IR enabled receiver

ANTENNA:

Housing and attached microphone form the antenna

BATTERY:

Two 1.5 Volt AA alkaline

BATTERY LIFE (DURACELL QUANTUM):

AA alkaline; No Phantom Power: 5h 0m, AA alkaline; 48V Phantom Power: 3h 30m

WEIGHT:

7.5 ozs. (211 grams) w/ AA batteries

DIMENSIONS:

4.25x1.62x1.38 inches