Lectrosonics R400a - Manual (Page 4)

R400A
LECTROSONICS, INC. 4
Introduction
This digital/analog hybrid technique has some very
beneficial properties. Because the information being
transmitted is digitally encoded, immunity to noise is
much higher than a compandor-based system can offer
and no artifacts are introduced under strong RF condi-
tions, and spectral and power efficiency and operating
range are not compromised.
Diversity Reception
SMARTDiversity ™ minimizes dropouts in situations
where multi-path reflections can cause serious prob-
lems. The phase diversity network and PIN diode RF
switches are controlled by the microprocessor using a
sophisticated algorithm to use both antennas simultane-
ously.
RF Front-End and Mixer
The R400A is frequency agile and can be set to operate
on any one of 256 frequencies within its tuning range.
To significantly reduce unwanted interference and inter-
modulation problems, the R400A’s front-end is tuned to
the desired frequency band and rejects or “tunes out”
unwanted out-of-band signals. Two tuned
HI-Q ceramic transmission line resonators prior to a low
noise, high current RF amplifier provide good selectivity.
A robust RF amplifier and LC bandbass filter provide
added insurance against strong RF interference. The
overall design ensures stability, selectivity and precise
gain in order to handle strong RF signals without input
overload.
IF Amplifiers and SAW Filters
The first IF low noise amplifier is controlled with feed-
back regulation and drives a quartz SAW (Surface
Acoustical Wave) filter. The 244 MHz SAW filter com-
bines sharp tuning, constant group delay, wide band-
width and excellent temperature stability, far superior to
conventional LC filters. The second mixer converts the
244 MHz first IF signal down to 10.7 MHz. The second
IF is filtered through two ceramic filters for sharp selec-
tivity, then itself is converted down to 300 kHz and fed
to the Digital Pulse Counting Detector.
The R400A is a high performance, triple-conversion,
frequency synthesized UHF receiver fully compatible
with all Lectrosonics 400 Series Digital Hybrid Wire-
less ® transmitters, 200 Series and 100 Series analog
transmitters and Lectrosonics IFB transmitters, plus
some analog transmitters from other manufacturers
(call Lectrosonics for details). The R400A features 256
user selectable frequencies and its proprietary audio
processing includes a digital signal processor (DSP) for
very low distortion, a superior signal to noise ratio and
two independent audio outputs, one balanced and one
unbalanced.
The receiver features a menu-driven LCD graphic dis-
play, a push-button POWER/PREV MENU control and
a dual function (push/rotate) PUSH FOR MENU/RO-
TATE TO SELECT control (hereafter called the MENU
control) as a convenient means of viewing and altering
user settings.
The MENU control provides simple and intuitive access
to change and adjust settings and operating levels.
Pushing the MENU control from the Main Window en-
ters the Top Menu which displays a choice of five sub-
menu options: SetUpRx, LockSet, SmartTune™, Scan
and Exit. Rotating the MENU control either highlights
a menu option or sets a parameter. Pushing the MENU
control either selects the highlighted menu option or
enters (or reenters) a menu.
Digital Hybrid Wireless ®
Lectrosonics Digital Hybrid Wireless ® (US Patent
7,225,135) uses innovative technology to combine the
new advantages of digital audio with the classic ad-
vantages of analog RF transmission. The result is the
superior sound quality of a digital system and the excel-
lent range of an analog system. A proprietary algorithm
encodes the digital audio information into an analog
format which can be transmitted in a robust manner
over an analog FM wireless link. The receiver employs
the latest filters, RF amplifiers, mixers and detector to
capture the encoded signal and a DSP (Digital Signal
Processor) recovers the original digital audio.