Lectrosonics UM250c User Manual download pdf (Page 5)

UHF Belt-Pack Transmitter

signal following the microphone preamp, just after the

compandor, to control the audio output muting of the

receiver. The pilot tone is filtered out of the audio signal

immediately after the detector in the receiver so that it

does not influence the compandor or various gain stages.

The basic benefit of the pilot tone squelch system is that

the receiver will remain muted until it receives the pilot

tone from the matching transmitter, even if a strong RF

signal is present on the carrier frequency of the system.

This is extremely important in applications that include an

automatic microphone mixer.

WIDE-BAND DEVIATION

The ±75kHz deviation improves the capture ratio, signal

to noise ratio and AM rejection of a wireless system

dramatically, compared to the more commonly used

±15kHz deviation.

LONG BATTERY LIFE

High efficiency circuits throughout the design allow over 2

hours of operation using a single 9 Volt alkaline battery.

(A 9V lithium battery will provide over 7 hours of opera-

tion.) The battery compartment is a unique mechanical

design which automatically adjusts to fit any brand of

battery. The battery contacts are spring loaded to prevent

“rattle” as the unit is handled.

FREQUENCY AGILITY

The transmitter section uses a synthesized, frequency

selectable main oscillator The frequency is extremely

stable over a wide temperature range and over time.

Two rotary switches, located on the side panel of the unit,

provide 256 frequencies in 100kHz steps over a 25.5MHz

range. This alleviates carrier interference problems in

mobile or travelling applications.

ANTENNA

At UHF frequencies, where wavelengths and antennas are

shorter than at VHF frequencies, a resonant length wire is

preferred over using the microphone cable as the antenna.

The antenna on the UM250B consists of a flexible 1/4

wavelength bronze cable, detachable via an SMA connec-

tor. The impedance of this connector is 50 Ohms.

Rio Rancho, NM – USA

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Lectrosonics UM250c User Manual Page 5