Lectrosonics LM User Manual download pdf (Page 4)

LM/IM

Introduction

Thank you for selecting the Lectrosonics LM or IM

frequency agile, belt-pack transmitter.

The design of these transmitters introduces at a moder-

ate cost the advanced technology and features of a

Lectrosonics belt-pack transmitter. The design is based

on the Digital Hybrid Wireless™ system (US Patent

Pending) which combines a digital audio chain with an

analog FM radio link. This digital process eliminates the

compandor and its problems, yet preserves the ex-

tended operating range of the finest analog wireless

systems. The IM is offered as part of the IS400 pack-

age and differs slightly from the LM in that its low-end

frequency response has been optimized for use with

musical instruments.

Both transmitters also preserve your investment. They

can emulate the compandor found in Lectrosonics 100

Series, 200 Series and IFB transmitters, and certain

transmitters from other manufacturers. (Call Lectroson-

ics for more details.) Changing the compatibility mode

is accomplished with a simple procedure that does not

require opening the unit.

Mechanically, the assemblies are rugged, machined

aluminum packages with removable, stainless steel wire

belt clips. Their input jack is a standard Lectrosonics 5-

pin type for use with electret lavaliere mics, dynamic

mics and line level signals. LEDs are provided on the

front panel to make quick and accurate level settings

without having to view the receiver. The battery com-

partment accepts any 9 volt battery (alkaline or lithium

recommended) and makes a positive connection via

self-adjusting contacts. The antenna is a super-rugged,

permanently attached 1/4 wavelength design made of

flexible galvanized steel cable.

Only the LM and IM transmitters are covered in this

manual. Companion receivers are covered in separate

manuals.

The Digital Hybrid Wireless™ system uses 75 kHz wide

deviation for an extremely high signal to noise ratio. The

switching power supplies provide constant voltages to

the transmitter circuits from the beginning (9.3 VDC) to

the end (5.5 VDC) of battery life. The input amplifier

uses an ultra low noise operational amplifier (op amp)

for quiet operation. It is gain controlled with a wide

range dual envelope input limiter that tames input signal

peaks over 30 dB above full modulation.

Digital Hybrid Technology

All wireless links suffer from channel noise to some

degree, and all wireless microphone systems seek to

minimize the impact of that noise on the desired signal.

Conventional analog systems use compandors for

enhanced dynamic range, at the cost of subtle artifacts

(known as “pumping” and “breathing”). Wholly digital

systems defeat the noise by sending the audio informa-

tion in digital form, at the cost of some combination of

power, bandwidth, operating range and resistance to

interference.

The Lectrosonics Digital Hybrid Wireless™ system

overcomes channel noise in a dramatically new way,

digitally encoding the audio in the transmitter 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 implementation of

an analog compandor but a technique which can be

accomplished only in the digital domain. (The patent is

still pending, so we cannot publish detailed information.)

Channel noise still has an impact on received signal

quality and will eventually overwhelm the receiver. The

Digital Hybrid Wireless™ system simply encodes the

signal to use a noisy channel as efficiently and robustly

as possible, yielding audio performance that rivals that

of wholly digital systems, without the power, noise and

bandwidth problems inherent in digital transmission. As

always, these advantages come at a cost. The Digital

Hybrid Wireless™ system requires fairly intensive

digital processing in both the transmitter and the

receiver. These processors cost money, take up space

and consume power. The Digital Hybrid Wireless

system also requires that the underlying RF link be of

excellent quality, with better frequency response and

distortion characteristics than that required by conven-

tional analog wireless systems.

Because it uses an analog FM link, Digital Hybrid

Wireless™ enjoys all the benefits of conventional FM

wireless systems, such as excellent range, efficient use

of RF spectrum, and long battery life. However, unlike

conventional FM systems, Digital Hybrid Wireless™ has

done away with the analog compandor and its artifacts.

LECTROSONICS, INC. 4

1 2 3 4 5 6 7 8 9 ... 15 16

Comments to this Manuals

No comments

Lectrosonics LM User Manual Page 4

Comments to this Manuals

Related products and manuals for Accessories communication Lectrosonics LM