General Technical Description - Lectrosonics UCR190 Operating Instructions And Troubleshooting Manual

Uhf compact receiver professional series wireless microphone system

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Table Of Contents

Table of Contents

Ant

Helical Resonator

GAsFET

Preamp

Helical Resonator

Filter

Battery

CH12

Jack

Off

+9V

Reg

Ext

Polarity

Protection

The UCR190 receiver is comprised of six major functional subsystems: the RF front-end amplifier, the double bal-

anced mixer/local oscillator, the first IF filter, the second IF filter and audio demodulator, the compandor, and the

balanced microphone level output circuit.

The RF front-end amplifier consists of a 5-section helical resonator for high selectivity. Between the first and second

helical resonators, is a low noise GAsFET amplifier. These amplifiers are designed to provide only enough gain to

make up for the inherent loss through the helical resonators. This combination of low front-end gain, coupled with the

extremely high selectivity of the cascaded helical resonators results in no overloading, even on extremely strong

signals. Rejection of out of band signals is maximized, and intermodulation products are suppressed.

The mixer stage consists of a high level double balanced diode mixer. The oscillator is biased from a regulated

supply, and includes Automatic Frequency Control (AFC) yielding stable performance over the entire life of the

battery. The local oscillator crystal operates at approximately 16 MHz, and can be adjusted above and below the

nominal frequency in order to place the 21.4 MHz IF in the center of the crystal filter's narrow passband. The high

selectivity of the IF crystal filter stage further minimizes the possibility of interference from signals on adjacent

frequencies.

The second IF filter and the audio demodulator, as well as the squelch and RF output LED drive are provided by one

monolithic integrated circuit. The second IF filter is centered on 1MHz, and drives a double tuned quadrature type

FM demodulator. The squelch circuit is a supersonic noise detector type and is factory set for a -20dB SINAD level

(about .5uV). The squelch level is regulated and temperature compensated to maintain a consistent squelch level

under all conditions.