Lectrosonics SSM Digital Hybrid Wireless Miniature Transmitter (A1: 470.100 to 537.575 MHz) - Manual (Page 4)

SSM, SSM-941, SSM/E01, SSM/E02, SSM/E06, SSM/X
LECTROSONICS, INC. 4
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 weakened signal condi-
tions; however, the Digital Hybrid Wireless system
handles this situation elegantly with barely 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.
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
B2 22, 23, 24 563.2 - 639.9
C1 24, 25, 26 614.4 - 691.1
C2 25, 26, 27 640.0 - 716.7
606* 606.0 - 631.5
*See Down Button Menu for more information
**Export Only (not available in US or Canada)
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
On older transmitter models, the left hand switch
makes steps in 1.6 MHz increments, the right
hand switch in 100 kHz increments.
Each block spans a 25.6 MHz band. A simple formula
is used to name the blocks according to the lowest
frequency in each one. For example, the block starting
at 512 MHz is named Block 20, since 25.6 times 20
equals 512.