Lectrosonics UCR195D User Manual download pdf (Page 5)

Diversity UHF Receiver

NO PRE-EMPHASIS/DE-EMPHASIS

The signal to noise ratio of the 195 system is high

enough to preclude the need for conventional pre-

emphasis (HF boost) in the transmitter and de-emphasis

(HF roll off) in the receiver. Pre-emphasis and de-

emphasis in an FM radio system usually provides about

a 10dB improvement in the signal to noise ratio of the

system, but the high frequency boost in the transmitter

must be removed in a purely complementary manner or

else the frequency response of the original audio signal

will be altered.

Pre-emphasis can also cause distortion in the IF filtering

stage in the receiver, since the high frequencies have

been boosted, which increases the level of the harmonics

in the FM signal. As this signal is passed through the IF

filters in the receiver, distortion can be produced, most

noticeable at full modulation. De-emphasis cannot be

applied until the signal is converted into audio, so there

is no way around this problem short of eliminating pre-

emphasis altogether. Neither of these problems occur in

the 195 system. The dual-band compandor in the 195

Series system essentially provides a dynamic pre-

emphasis/de-emphasis function with extremely low

distortion.

EXCEPTIONAL THERMAL STABILITY

If temperature shifts cause the oscillators to drift, or

values to change in the detector, serious distortion will

result. The components in the 195 Series systems meet

very stringent tolerances for thermal drift. System

distortion in the 195 series remains at very low levels

over a very wide temperature range. This is especially

important in applications where the receiver and/or

transmitter must be operated near heat generating

devices, outdoors in direct sunlight, or with the receiver

mounted in an equipment rack.

Rio Rancho, NM – USA

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Lectrosonics UCR195D User Manual Page 5