The DECADE TRC-800 and TRC-800S are high-performance and high-reliability Hi-Fi Stereo FM Transmitters designed for various applications, including drive-in theaters, private touristic and attraction sites, special events, and general indoor use. These transmitters operate within the commercial FM broadcast band of 87.9 MHz to 107.9 MHz, allowing signals to be received on any standard FM receiver. The TRC-800 is a 1 Watt Hi-Fi mono FM transmitter, while the TRC-800S is a 1 Watt Hi-Fi stereo FM transmitter. Both models are certified under FCC Part 73 regulations, though a license or experimental license is required for operation in the USA.
Function Description:
The core function of these devices is to transmit audio signals over the FM band. They achieve this through a sophisticated design that includes:
- Crystal Controlled VCO (Voltage Controlled Oscillator): Ensures precise and stable frequency generation.
- Stereo Generator (TRC-800S only): For transmitting stereo audio signals. The TRC-800 operates in mono mode.
- RF Power Amplifier: Boosts the radio frequency signal to the desired output power.
- Spurious Filter: Reduces unwanted harmonic emissions, ensuring a clean transmission.
The transmitters accept both left and right audio signals through two types of input connectors, offering versatility in connecting to various audio sources.
Important Technical Specifications:
Radio Section (Common to TRC-800 and TRC-800S):
- Modulation: FM, with a deviation of 75kHz.
- Frequency Range: Programmable from 87.9 MHz to 107.9 MHz.
- Frequency Precision: 0.0008% or better.
- Harmonics Rejection: 50 dB minimum, 60 dB typical.
- Maximum Output Power: 600 mW minimum, 1 W typical, 1.6 W maximum.
- Load Impedance: 50 Ohms typical.
- Antenna Connector: UHF-F (PL-F) type.
- Homologation Standard: RSS-153.
- Control: Output power adjustment.
Audio Section (TRC-800 - Mono):
- Mode: Mono (HI-FI).
- Frequency Response: 20 Hz - 20,000 Hz, @-1dB.
- Total Harmonic Distortion: 0.05% maximum.
- Signal to Noise Ratio: 70 dB minimum.
- Dynamic Range: 80 dB minimum.
- Input Impedance: 600 Ohms balanced (XLR), 10K Ohms unbalanced (1/4").
- Connectors: XLR3 and 1/4".
- Input Level: Balanced: -15dBm min., +22 dBm max. Unbalanced: -15 dBm min., +39 dBm max. (70 VRMS).
- Indicators: Over modulation.
- Control: Input level.
Audio Section (TRC-800S - Stereo):
- Mode: Stereo/mono (HI-FI).
- Frequency Response: 20 Hz - 15,000 Hz, @-1dB (Broadcast standard).
- Total Harmonic Distortion: 0.05% maximum.
- Signal to Noise Ratio: 65 dB minimum.
- Dynamic Range: 80 dB minimum.
- Stereo Separation: 35 dB minimum, 40 dB typical. (The minimum required separation for FM transmitters is 25 dB. The best receivers have a separation of 40dB, so the effective separation is more a matter of the quality of the receiver.)
- Input Impedance: 600 Ohms balanced (XLR), 10K Ohms unbalanced (1/4").
- Connectors: 2 x XLR3 and 2 x 1/4".
- Input Level: Balanced: -15dBm min., +22 dBm max. Unbalanced: -15 dBm min., +39 dBm max. (70 VRMS).
- Indicators: Over modulation and stereo indicator.
- Controls: Input level and mono/stereo selector.
Miscellaneous (Common to TRC-800 and TRC-800S):
- Power Requirements: 120 V, 60 Hz, 9 VA.
- AC Protection: Grounded AC plug and 500 mA slow blow, 120 V fuse.
- Dimensions: 19" x 10" x 1.75" (48 cm x 25 cm x 4.5 cm), 1 rackmount space.
- Weight: 5 lb (2.27kg).
Usage Features:
- Versatile Audio Inputs: Both models feature XLR3 600 Ohms balanced inputs and 1/4" 10K Ohms unbalanced inputs, accommodating a wide range of audio sources like CD players, tape decks, mixing boards, and cinema projectors.
- Input Level Control: A dedicated "INPUT LEVEL" control on the front panel allows users to adjust the audio input to achieve optimal modulation, preventing distortion.
- Overmodulation Indicator (OVER LED): A red "OVER" LED lights up when modulation exceeds 200%, signaling potential distortion. Its lengthened holding time aids in better perception of overmodulation.
- Mono/Stereo Selector (TRC-800S only): The TRC-800S includes a front-panel selector to switch between mono and stereo modes, offering flexibility for different applications. In mono mode, only the RIGHT input is active, and the LEFT input is ignored.
- Antenna Placement Guidance: The manual provides recommendations for antenna placement to optimize signal coverage and minimize attenuation from building materials like concrete and steel, while leveraging the permeability of windows.
- Regulatory Compliance: Designed to operate within CRTC (Canadian Radio-television and Telecommunications Commission) and DOC (Department Of Communications, Canada) regulations for low-power FM transmitters, with specific guidelines for indoor and outdoor use.
Maintenance Features:
- Low Maintenance Design: No specific maintenance is required to keep the transmitter in top operating condition.
- External Cleaning: For external cleaning, a soft, damp cloth and mild soap are recommended.
- Frequency Selection:
- The transmitting frequency is factory-programmed but can be changed by the user.
- This involves selecting the appropriate "bits switch" code from a provided table and setting the physical "bits switch" on the main board.
- A DC voltmeter is used to connect to alligator clips on the board to monitor the VCO tuning voltage.
- "COARSE" and "FINE" tuning adjustments allow for precise voltage setting (between 3.0 and 5.0 volts) to stabilize the transmitter on the selected frequency.
- RF Power Level Adjustment:
- A small white trimpot labeled "POWER (PWR)" near the "bits switch" allows for adjustment of the RF power level.
- Turning it clockwise increases power, and counterclockwise decreases it.
- It is mandatory to check the DC voltage (aligator clips) to ensure the oscillator is within its capture zone (3 to 4 volts DC) when adjusting RF power.
- Monitoring Recommendation: It is strongly suggested to keep a watt meter plugged in permanently between the transmitter's output and the transmission line to ensure continuous monitoring of the complete system. The SWR-14 wattmeter is available from DECADE TRANSMITTERS.
DECADE Transmitters reserves the right to make changes or improvements in the manufacturing or design of its products, which may affect specifications.
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