Lectrosonics UCR211 User Manual download pdf (Page 4)

UCR211

GENERAL TECHNICAL DESCRIPTION

The UCR211 is a portable, high performance, triple-

conversion, frequency synthesized, UHF receiver fully

compatible with all Lectrosonics 200 series transmitters.

The RF performance is extremely stable over a very

wide temperature range, making the UCR211 perfectly

suited to the rough environmental conditions found in the

field. The proprietary audio processing includes a dual-

band compandor for very low distortion and a superior

signal to noise ratio. The Smart Squelch system is

operated by a pilot tone and mutes the audio output

directly at the output connector.

The UCR211 features a menu-driven LCD graphic

display and a three button control panel as a convenient

means of viewing and altering user settings. The Main

Window, for example, shows the pilot tone indicator,

antenna diversity phase, RF level, audio level, receiver

battery status and transmitter battery status. It is also

possible to bypass the pilot tone from the Main Window.

Other display windows show operating frequency, audio

output level, battery status in tenths of volts, test tone

status and provide for selection of levels or functions

using the select buttons. The frequency scan mode

provides a graphical means of observing all signals “on

the air” within the frequency range of the receiver in

order to find operating frequencies that are free of

interference.

DIVERSITY RECEPTION

The UCR211 antenna phase diversity technology with

SMART Diversity

minimizes dropouts in situations

where multi-path reflections can cause serious problems.

The phase diversity network and PIN diode RF switches

are controlled by the microprocessor using a sophisti-

cated algorithm. This design keeps the receiver compact

enough for camera mounting or shoulder bag applica-

tions.

RF FREQUENCY TRACKING FRONT-END

AND MIXER

The receiver is frequency agile and can be set to operate

on any one of 256 frequencies within the tuning range.

To significantly reduce unwanted interference and

intermodulation problems, the UCR211 has a frequency

selective front-end section that tracks and tunes to the

desired signal frequency and rejects or “tunes out”

unwanted interfering signals. The design consists of four

varactor tuned ceramic transmission line resonators

controlled by the microprocessor to provide good selec-

tivity. The low noise high current RF amplifier was

designed with feedback regulation for stability and

precise gain in order to handle stronger RF signals

without output overload. The first mixer is of new GaAs

technology that has a very high third order intercept

point. This produces a robust front-end that is as selec-

tive as fixed single frequency designs and is suitable for

use in close proximity to other receivers and transmitters

commonly used in field production “bag” systems.

MICROCONTROLLER, PLL AND VCO

CIRCUITS

The 8-bit microprocessor is truly the “heart” of the

UCR211 receiver. It monitors user command inputs from

the front panel control buttons and numerous other

internal signals such as RF level, audio levels, pilot tone

levels and external/internal power voltages. Outputs

from the microcontroller operate the front-end tuning,

PLL/VCO circuits, antenna phase switch, drive the LCD

display and backlight, and control the squelch and audio

output attenuator. The microcontroller also generates an

audio test tone used to adjust input levels of the equip-

ment being fed by the receiver. The UCR211 design and

the advanced technology of the microprocessor control

arguably set a new standard in wireless microphone

development.

IF AMPLIFIERS AND SAW FILTERS

The first IF low noise amplifier is controlled with feed-

back regulation and drives the first of two quartz SAW

(Surface Acoustical Wave) filters. The 244 MHz SAW

filters combine sharp tuning, constant group delay, wide

bandwidth and excellent temperature stability, far supe-

rior to conventional LC filters. The 244 MHz first IF

signal is converted to 10.7 MHz, filtered through two

ceramic filters for sharp selectivity, then converted to 300

kHz in one integrated circuit.

DIGITAL PULSE COUNTING DETECTOR

The UCR211 receiver uses an elegantly simple, yet

highly effective digital pulse detector to demodulate the

FM signal, rather than a conventional quadrature detec-

tor. This unusual design eliminates thermal drift, im-

proves AM rejection, and provides very low audio

distortion.

TRI-MODE DYNAMIC FILTER

The audio signal is passed through a “dynamic noise

reduction circuit” that automatically controls the audio

cutoff frequency. The cutoff frequency of this filter is

varied automatically by measuring the amplitude and

frequency of the audio signal and the quality of the RF

signal. The audio bandwidth is held only to that point

necessary to pass the highest frequency audio signal

present at a given moment. This results in a dramatic

reduction of the higher frequency “hiss” normally present

particularly with low RF signal levels. During passages

of high frequency audio content, this filter dynamically

passes the signals with no decrease in high frequency

content. This filter has proven very effective and is

totally transparent.

PILOT TONE MUTE

The UCR211 uses a pilot tone muting technique in order

to protect against the reception of stray signals. The

Lectrosonics transmitter adds an inaudible signal, known

as the pilot tone, to the transmitted signal. The receiver

detects (and removes) the pilot tone, and is thus able to

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