Lectrosonics Inc SSMA1 Benutzerhandbuch

4

Introduction

Three Block Tuning Range

The SSM transmitter tunes across a range of over 76 

MHz. This tuning range covers three standard Lectro-

sonics frequency blocks.

TUNING RANGE

BLOCK

BLOCK

BLOCK

Four tuning ranges are available covering standard 

blocks as follows:
  Range 

Blocks Covered 

Freq. MHz 

A1

470, 19, 20

470.1 - 537.5

B1

21, 22, 23

537.6 - 614.3

C1

24, 25, 26

614.4 - 691.1

D1*

27, 28, 29

691.2 - 767.9

To simplify backward compatibility with earlier Digital 

Hybrid Wireless

®

 equipment, block numbers are pre-

sented along with frequencies in LCD screens.

About Frequency Blocks

A 25.6 MHz band of frequencies, referred to as a 

Block, came about with the design of the first frequency 

tunable Lectrosonics wireless products. These prod-

ucts provided two 16-position rotary switches to select 

frequencies as shown in the illustration below. A logical 

method of identifying the switch positions was using 16 

character hexadecimal numbering. This naming and 

numbering convention is still used today.
The 16 switch positions are numbered 

0 (zero) through 

F, presented in a two-character designation such as 

B8, 5C, AD, 74, etc. The first character indicates the 

position of the left hand switch and the second charac-

ter indicates the position of the right hand switch. This 

designator is commonly called a “hex code.”

FREQUENCY

1.6MHz 100kHz

0 1

2

3

4

5

6

7

8

9

A

B

C

D

E F

0 1

2

3

4

5

6

7

8

9

A

B

C

D

E F

Each block spans a 25.6 MHz band. A simple formula 

is used to name the blocks according to the lowest fre-

quency in each one. For example, the block starting at 

512 MHz is named Block 20, since 512 divided by 25.6 

equals 20.

About Digital Hybrid Wireless

®

US Patent 7,225,135
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, however, it is often at the cost of one 

or more issues regarding power, bandwidth, operating 

range and resistance to interference.
The Lectrosonics Digital Hybrid Wireless

 

system over-

comes 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 informa-

tion 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.
Since the RF link between transmitter and receiver is 

FM, channel noise will increase gradually with in-

creased operating range and weak signal conditions, 

however, the Digital Hybrid Wireless system handles 

this situation elegantly with rarely audible audio artifacts 

as the receiver approaches its squelch threshold.
In contrast, a purely digital system tends to drop the 

audio suddenly during brief dropouts and weak signal 

conditions. 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 purely digital systems, without the 

power, noise and bandwidth problems inherent in digital 

transmission. 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.