Lectrosonics UT200c - Manual (Page 4)

PILOT TONE SQUELCH
The 200 system utilizes an ultrasonic tone modulation of the carrier to operate the receiver squelch. This “pilot tone”
consists of a 32kHz signal mixed with the audio 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 such as with an automatic microphone mixer.
WIDE-BAND DEVIATION
75kHz deviation improves the capture ratio, signal to noise ratio and AM rejection of a wireless system dramatically.
Almost all other wireless systems use less than 75kHz deviation.
LONG BATTERY LIFE
High efficiency circuits throughout the design allow over 4 hours of operation using a single 9 Volt alkaline battery
(over 12 hours with a new lithium battery.) The battery compartment is a unique mechanical design which automati­
cally adjusts to fit any brand of alkaline or lithium battery. Battery replacement is easily accomplished by releasing
the bottom and removing the battery cover. The battery contacts are spring loaded to prevent “rattle” as the unit is
handled. The UT200C contains a battery status monitoring circuit which monitors and sends the battery status to the
UDR200B receiver. The battery status is displayed on the front of the receiver.
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 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
The high output antenna utilizes the lower half of the printed circuit boards as one radiating element, with the upper
half of the PC boards and mic capsule as the other half of the dipole configuration. This allows the mic to be held in
any position, since the user’s hands have little or no effect on the radiated power.
MICROPHONE ELEMENT
The UT200C includes the Lectrosonics VariMic mic element. The VariMic is an cardioid condenser back electret
microphone that is adapted for the unique circumstances of wireless microphones. The problems it solves are
dynamic range, handling noise and low frequency noise (rumble or wind).
In the VariMic, an unusual pumped source FET circuit increases the usable dynamic range 12dB and greatly reduces
distortion, just as if the FET were being supplied with 48 Volts. In addition, a unique 16 position sensitivity control at
the element itself can adjust the sensitivity in 15 steps over a 15 dB range. This is in addition to the normal gain
control in the wireless microphone. The result is the widest dynamic range of any condenser mic in a wireless
microphone.
The VariMic has a three point damped rubber suspension to reduce high frequency handling noise and a generous
sized windscreen to keep wind noise and breath pops away from the microphone.
Low frequency noise is much more of a problem with wireless microphones than with conventional microphones.
With a regular mic, low frequency wind noise, breath thumps or handling rumble can be filtered out at the control
board before the noise causes problems with the following electronics or speaker systems. But with a wireless
microphone, the electronics that will be overdriven are right in the wireless microphone. Filtering at the control board
is much too late. To solve this problem, the VariMic has a low frequency filter that is so sharp that it can remove low
frequency noise without affecting any wanted vocals. It consists of a 36 dB per octave filter circuit to sharply remove
low frequency noise below 75 Hz without affecting vocal fundamentals. The lowest operatic bass voice fundamental is
82 Hz. Isn’t it nice to know that it will come ripping right through.
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