How to get the most from your RX Lectrosonics UCR411

The UCR411A receiver provides professional performance

and a versatile feature set in a compact design for field

and location production. All settings are made from the

front panel with a powerful LCD interface, making the unit

ideal for use in portable bag systems, on sound carts, and

in rack mount multi-couplers. An RF spectrum analyzer

is built into the receiver to alleviate interference problems

in an increasingly congested RF spectrum. The receiver

tunes across its 25.6 MHz tuning range and records RF

activity with markers on the LCD screen. Finding clear

operating frequencies is a quick, simple process.

The mechanical design of the receiver combines field

proven features developed over many years of experience

in motion picture and television production markets. The

machined aluminum housing and panels are surfaced with

electrostatic powder coated and anodized finishes with laser

etched markings to withstand the rigors of field production.

DSP Compatibility Modes

The native, compandor-free Digital Hybrid operating

mode works with all Lectrosonics hybrid transmitters. DSP

"compatibility modes" allow the receiver to also work with

companded analog transmitters from Lectrosonics and

some from other manufacturers. This expands the usefulness

of the receiver and provides the backward compatibility

needed to give existing customers an economical

upgrade path.

Frequency Tracking Front-End Filters

The front-end consists of four transmission line resonators

with variable

capacitance applied

to each resonator to

retune it as the frequency

is changed.

The tuning range covers

a full 25.6 MHz

block of frequencies.

The design provides

tunable, narrow

filtering as selective

as most fixed frequency designs, with the overload

performance of the best front-ends available. The result is

extended operating range in even the most congested RF


*US Patent 7,225,135

Digital Hybrid Wireless™ technology* is a revolutionary

new design that combines digital audio with an

analog FM radio link to provide outstanding audio

quality and the exemplary RF performance of the finest

analog wireless systems.

The design 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. Instead, it is a technique which

can be accomplished only in the digital domain.

The process eliminates a compandor and its artifacts,

expanding the applications to include test and measurement

of acoustic spaces and musical instruments.


A conventional squelch design faces several compromises.

* Squelch too aggressively and audio may be lost.

* Squelch too little and excessive noise may be heard.

* Respond too rapidly and the audio will sound "choppy."

* Respond too sluggishly and entire words or syllables

can be cut off.

SmartSquelch™ achieves an optimal balance of these tradeoffs

by combining several techniques that remove distracting

noise without the squelching action itself becoming a distraction.

The circuitry will perform the following functions:

* Wait for a complete word or syllable before squelching.

* Assess recent squelching history and RF signal


* Assess audio content to determine available masking.

By adjusting squelching behavior dynamically for the optimal

result under varying conditions, the receiver can deliver acceptable

audio quality from otherwise unusable signals.


Microprocessor controlled antenna phase combining

is utilized for diversity reception to keep the receiver

small, yet still deal effectively with multi-path dropouts.

The embedded firmware analyzes RF level, the rate of

change of RF level and the audio content to determine

the optimum timing for phase switching, and the optimum

antenna phase. This adaptive technique operates over a

wide range of RF levels to anticipate dropouts before they

occur. The system also employs "opportunistic switching"

to analyze and then latch the phase in the best position

during brief squelch activity.


With a noise floor at -120 dBV and a frequency response

to 20 kHz, high frequency noise in the source audio is

more apparent than in conventional wireless systems.

The Smart Noise Reduction algorithm works by attenuating

only those portions of the audio signal that fit a statistical

profile for randomness or "electronic hiss." Because

it isn't simply a sophisticated variable low pass filter as

in earlier analog designs, much greater transparency is

obtained. Desired high frequency signals having some

coherence such as speech sibilance and tones are not


The Smart NR algorithm has three modes, selectable

from the front panel LCD. When switched OFF, no noise

reduction is performed. When switched to NORMAL, the

factory default setting, enough noise reduction is applied

to remove most of the hiss from the mic preamp

and some of the hiss from lavaliere microphones. When

switched to FULL, enough noise reduction is applied to

remove most of the hiss from nearly any signal source of

reasonable quality, assuming levels are set correctly at

the transmitter.

Analog RF Links

A digitized audio or RF signal occupies a good deal more

bandwidth than the original analog signal. A digital transmission

over the air requires some combination of additional

power, more RF bandwidth and/or compression of

the audio data to achieve adequate operating range and

keep the energy inside the defined spectral mask. Because

of this, digital wireless microphones typically lack

the operating range of conventional FM systems.

With regard to using RF power and spectrum efficiently,

an analog RF link has many advantages in wireless mic

systems, among them long battery life, excellent range,

and the ability to use many systems in close proximity

without interference.

DSP-Based Pilot Tone

The 400 Series system design utilizes a DSP generated

ultrasonic pilot tone to control the receiver audio muting

(squelch). Brief delays at turn-on and turn-off eliminate

thumps, pops or other transients that can occur when

the power is switched on or off. The pilot tone frequency

is different for each of the 256 frequencies in the tuning

range of a system (frequency block) to eliminate squelch

problems in multichannel systems where a pilot tone

signal can appear in the wrong receiver via intermodulation

products. The DSP generated pilot tone also survives

mishandling much better than fragile crystal-based pilot

tone systems.

High Current, Low Noise Amplifiers

The gain stages in the front end use special transistors in

a feedback regulated high current circuit that combines

low noise, low gain, and high power. The design takes all

three of these parameters into consideration at once, to

provide low noise RF amplification, excellent sensitivity

and extremely low susceptibility to intermodulation.

Combining the high power gain stages with the tracking

front end produces a receiver that is immune to single

and multiple interfering signals close to the operating

frequency and in addition, strongly rejects signals that are

much farther away.

Surface Acoustic Wave (SAW) Filter

SAW filters in the first IF section operating at 244 MHz

combine sharp skirts, constant group delay, and wide

bandwidth in one filter. These quartz filters are temperature

stable. This special type of filter allows primary

filtering as early as possible, at as high a frequency as

possible and before high gain is applied to the signal. After

the sharp filtering action of the SAW filters, the signal

is converted to the second IF at 10.7 MHz, then finally to

the third IF at the low frequency of 300 kHz, where the

counting detector generates the audio signal.