Lectrosonics LT (A1: 470.100 - 537.575 MHz, BLOCKS 470, 19, 20)
Digital Hybrid Wireless Belt-Pack Transmitter. The LT transmitter offers a full set of professional features in a compact, rugged package.
The unit is compatible with all Digital Hybrid Wireless receivers and even some from other manufacturers, making it comfortable in a wide variety of applications from video production to theater, stage and house of worship.
The LT can be configured to operate as a "one touch" device with a single power on/off switch on the top panel, or with full access to all operational parameters using the side panel membrane switches and LCD interface. The top panel switch can also be configured to provide a mute or talkback function.
About Digital Hybrid Wireless
All wireless links suffer from channel noise to some degree, and all wireless microphone systems seek to minimize the impact of that noise on the desired signal. Conventional analog systems use compandors for enhanced dynamic range, at the cost of subtle artifacts (known as "pumping" and "breathing"). Wholly digital systems defeat the noise by sending the audio informa- tion in digital form, at the cost of some combination of power, bandwidth, operating range and resistance to interference.
The Lectrosonics Digital Hybrid Wireless system over- comes 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 informa- tion via an analog FM wireless link. This proprietary algorithm is not a digital implementation of an analog compandor but a technique which can be accomplished only in the digital domain.
Since the RF link between transmitter and receiver is FM, channel noise will increase gradually with in- creased operating range and weak signal conditions, however, the Digital Hybrid Wireles system handles this situation elegantly with rarely audible audio artifacts as the receiver approaches its squelch threshold.
In contrast, a purely digital system tends to drop the audio suddenly during brief dropouts and weak signal conditions. The Digital Hybrid Wireless system simply encodes the signal to use a noisy channel as efficiently and robustly as possible, yielding audio performance that rivals that of purely digital systems, without the power, noise and bandwidth problems inherent in digital transmission. Because it uses an analog FM link, Digital Hybrid Wireless enjoys all the benefits of conventional FM wireless systems, such as excellent range, efficient use of RF spectrum, and long battery life.
Frequency selection is provided in 100 kHz or 25 kHz steps with up to 3072 channels available covering three standard Lectrosonics 25.6 MHz bands. Frequencies are displayed on the LCD in MHz and in a hex code used with earlier Lectrosonics equipment.
Deviation has a direct effect on the dynamic range and signal to noise ratio of an FM system. The greater the deviation, the wider the dynamic range and the better the signal to noise ratio. In the Digital Hybrid Wireless mode, the system operates with a maximum of +/-75 kHz of deviation. The resulting 180 kHz of occupied bandwidth just fits inside the government specified spectral mask of 200 kHz. In order to make this pos- sible, an advanced, DSP-controlled limiter is used to prevent signal peaks from exceeding the maximum allowed bandwidth, but not cause distortion.
The result of all this is that the audio quality is outstand- ing, rivaling a hard-wired microphone. The system deliv- ers a very wide dynamic range, and can handle loud signal peaks without distortion.
Servo Bias Input and Wiring
The LT input preamp is a unique design that delivers audible improvements over conventional transmitter inputs. The transmitters are easier to use and much harder to overload. It is not necessary to introduce pads on some mics to prevent overload of the input stage, divide the bias voltage down for some low voltage mics, or reduce the limiter range at minimum gain settings.
Two different microphone wiring schemes are available to simplify and standardize the configuration. Simpli- fied 2-wire and 3-wire configurations provide several arrangements designed for use only with servo bias inputs to take full advantage of the preamp circuitry. Other wiring schemes are compatible with Servo Bias and conventional inputs.
A line level input wiring provides an extended frequency response with an LF roll-off at 35 Hz for use with instru- ments and line level signal sources.
Covers three standard frequency blocksDigital Hybrid Wireless for compandor-free audioSelectable 50 or 100mW output powerCompatibility modes for use with analog receivers25 or 100 kHz tuning steps for up to 3072 selectable frequenciesIntegrated multi-function switch for mute or talkback modesWide range input gain control in 1 dB stepsIR port for setup with IR enabled receiversUSB port for firmware updatesMenu selectable mic or instrument inputOptional battery eliminatorDetachable antenna
Operating Frequency: Band A1: 575 537.600 - 614
Frequency Selection Steps: Selectable; 100 kHz or 25 kHz
RF Power output: 50 or 100 mW
Pilot tone: 25 to 32 kHz; 5 kHz deviation (Digital Hybrid mode)
Frequency Stability: ± 0.002%
Deviation: ± 75 kHz max. (Digital Hybrid mode)
Spurious radiation: 60 dB below carrier
Equivalent input noise: -120 dBV (A-weighted)
Input level: Nominal 2 mV to 300 mV, before limiting Greater than 1V maximum, with limiting.
Mic: 300 OhmLine: 2k Ohm
Input limiter: DSP controlled, dual envelope "soft" limiter with greater than 30 dB range
Gain control range: 44 dB; digital control
Modulation indicators: Dual bicolor LEDs indicate modulation of -20, -10, 0 and +10 dB referenced to full modulation, LCD bar graph
Controls: Top panel toggle switch; programmable as power, mute, talkback or none (off) function, Side panel membrane switches with LCD interface for power on/off and all setup and configuration controls
Audio Input Jack: Switchcraft 5-pin locking (TA5F)
Antenna: Galvanized steel, flexible wire
Battery: Two AA; alkaline, lithium, NiMH rechargeable
Battery Life: Duracell Quantum: 4.75 hours, Eneloop 2400 mAH NiMH: 5.5 hours
Weight: 5.8 ounces (141 grams), including lithium AA batteries and wire belt clip
Dimensions: 3.2 x 2.4 x .9 in. (81 x 61 x 20 mm)
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