Harris Digit 55 watt transmitter/ exciter Start Price USD 2,000.00 Current Price USD 2,000.00 Time Left - Bid Count 0 Buy It Now Price USD 2,500.00 Reserve Price - Start Time Saturday, August 30, 2008 End Time Sunday, August 31, 2008 Location Lubbock, TX See more about 'Harris Digit 55 watt transmitter/ exciter ' Description Harris DIGIT CD, globally the world’s first commercial, digitally modulated FM exciter, employs Direct Digital Synthesis (DDS) technology to generate a signal with true 16-bit digital audio quality. Using a DDS device with a direct interface to all standard AES3-1992 data rates, DIGIT CD makes it possible to maintain an all-digital path from the studio source through the FM modulator. By eliminating all intermediate A/D and D/A conversions, noise and distortion added between the studio source and the output of the digital FM modulator are zero. Although DIGIT CD is revolutionary, its technology is easy to understand. Figure 1 is a top level block diagram of signal paths. The digital modulator uses a 32-bit Direct Digital Synthesis (DDS) device and supporting circuitry to digitally generate the FM carrier complete with stereo and SCA modulation. A digital “tuning number” sets the output frequency of the DDS device in the 5 to 6MHz range. Incoming digital program data at a rate of about 500kHz is used to offset the tuning number to modulate the output signal. The frequency source uses a crystalreferenced PLL synthesizer to generate a low noise RF mixing signal for the upconverter. The source frequency can be set either internally by a DIP-switch array, or externally using a 25-bit parallel data interface through a D connector on the back panel of the exciter. The DIGIT CD can also use an external 10MHz reference for frequency locking in FM booster applications (optional). Outputs of the digital modulator and the synthesized frequency source are converted to the final output frequency in the upconverter. Innovative bandpass filters, which do not change the FM sideband structure, provide -80dBc or better filtering of the FM signal. The output of this circuitry is a very pure FM signal on the assigned carrier frequency, ready for amplification by the following stages in the exciter/transmitter. The RF power amplifier boosts the bandpass filter output power to the range of 1 to 55 watts to drive the FM transmitter. The amplifier uses rugged MOSFET devices and is self-protecting for load mismatch and overtemperature. An optional harmonic filter with RF sample port is available, allowing DIGIT CD to be used directly on the air as a low power transmitter. The digital/SCA interface module accepts AES3 digital audio and multiple RDS/SCA inputs, and includes an on-board DSP stereo generator to feed data directly into the digital modulator. A special “look-ahead” peak limiter controls overmodulation peaks before they can occur, and also allows high average modulation without the distortion caused by composite clipping. The digital/SCA interface module supports standard AES3-1992 data rates and provides a direct, single cable connection from the AES3 stereo output of typical digital coding and processing systems. As an emergency feature, one of the analog SCA ports of the digital/SCA interface module can be used as an analog composite stereo input if the normal AES3 path is not available. The digital/SCA interface module can be substituted for the analog/SCA interface module. This allows stations to use the digital exciter now with analog baseband sources, and then upgrade DIGIT® to work with an alldigital program path later, when their digital studio-transmitter link is installed. The analog/SCA module allows DIGIT CD to be used with analog baseband channels. It provides compatibility with the same composite baseband interface, monaural audio, and analog 57-92kHz SCA subcarrier input port used on the Harris THE-1 FM exciter and many other analog FM exciters. This module converts baseband input signals to the composite digital format needed for the digital modulator. When an AES3 program is available, the digital module may be substituted for the analog module to provide an all-digital path from the studio through generation of the FM broadcast signal. General Power Output Range: 1 to 55 watts, user adjustable. RF Output Impedance: 50 ohms, BNC female connector; open and short circuit protected. RF Harmonic and Spurious Suppression: Meets or exceeds all FCC and IC requirements and CCIR recommendations for a 55 watt transmitter when used with optional low pass filter. Frequency Range: 87 to 108MHz, digitally programmable in 50Hz increments. Frequency Stability: ±150Hz, 0°C to 50°C ambient temperature range (using internal frequency reference). External Frequency Control: Capable of locking to an external 10MHz reference for use in FM synchronous applications when fitted with optional DIGIT CD Sync Board (992- 9850-001). Sync input requirement: 2.82Vp-p or TTL level. Sync input connector: BNC female. The Harris Digit comes with the analog and digital I/O modules and some connector parts. Fantastic quality of sound no matter if your using a low power transmitter application or Full blown Transmitter. Sounds Supurb! This exciter is priced to sell. New ones are up to $8000. this is like new only used as backup so the savings are ideal to get you back on the air or for low power applications. Features/Benefits Direct interface to digital sources/STLs eliminates intermediate A/D and D/A conversions which add distortion, noise, and system cost. Digital Signal Processor (DSP) synthesis of stereo provides perfect stereo, with none of the signal degradation resulting from the amplitude and phase limitations of analog baseband. Modulator frequency response to DC provides performance unaffected by large transients in program sources (STL carrier squelch, etc.) and elimination of off-air time from AFC/PLL overload or relock. Externally Controlled Carrier Frequency Synchronization. Carrier synchronization is an important feature for on-carrier FM booster systems to provide controlled and stable service with a minimum of interaction in the coverage areas of the main and booster transmitters. An optional feature of the new DIGIT CD will allow an external 10MHz sychronization frequency standard referenced to Global Positioning System (GPS) satellites. This approach eliminates the current need to transport a frequency reference subcarrier or tone to each booster. GPS synchronization can provide a large improvement in carrier stability - up to 5 parts in 10-12, depending on the GPS receiver used. Synchronous AM reduction circuit. The DIGIT CD includes special system optimization circuitry to reduce synchronous AM, no matter where it may originate in the transmitter or output system. This feature can be very useful to reduce the synchronous AM produced in narrowband transmitter stages, and can improve system performance into narrowband filters, combiners and antenna systems. Exact modulation metering at any frequency ensures true peak modulation level as read from modulation data. Place a Bid!