The **adjacent frequency modulator**, also known as an RF modulator, FM modulator, or TV modulator, is a key component in the front-end equipment of a cable TV system. Its primary function is to take video (VIDEO) and audio (AUDIO) signals from various sources—such as AV set-top boxes, satellite receivers, DVD players, computers, video cameras, or TV demodulators—and modulate them onto a stable high-frequency RF carrier signal. The video signal is typically amplitude-modulated, while the audio is frequency-modulated. Depending on the television standard used in different regions, adjacent frequency modulators come in three types: PAL, NTSC, and SECAM. In China, the PAL-D system is widely adopted.
**How to Adjust the Adjacent Frequency Modulator**
1. Connect standard video and audio test signals to the input ports of the TV modulator. Then, connect a field strength meter to the output port and a standard demodulator to the output side for monitoring.
2. Adjust the output image and set the code switch to select the desired carrier frequency.
3. Use the input video amplitude control to set the video modulation level to 87.5%, which is the standard for most systems.
4. Measure the image carrier level and the sound carrier level using the field strength meter. Adjust the audio level so that the A/V ratio matches the design specifications.
5. Finally, adjust the output level attenuation knob to ensure the RF output level matches the required operating level.
**Key Features of the Adjacent Frequency Modulator**
1. This modulator operates in the 48MHz–750MHz frequency range, using the fixed channel output method of the PAL-D system.
2. It incorporates a dual-phase-locked loop (PLL) design for both image and audio frequencies, ensuring greater stability and accuracy.
3. High-quality broadcast-grade modulation chips from well-known manufacturers such as Toshiba, Motorola, Intech, Texas Instruments, and Fairchild are used in its construction.
4. It employs high-performance surface acoustic wave (SAW) filters, providing vestigial sideband suppression of over 65dB.
5. The device offers a strong RF output of up to 110dBµV, with stable amplitude and precise frequency control.
6. It features a unique filtering technique, achieving out-of-band suppression of more than 65dB.
7. Key parameters such as image modulation, audio frequency offset, A/V ratio, and RF output level can all be adjusted for optimal performance.
8. Designed with a 19-inch standard chassis, it ensures easy and standardized installation in rack-mounted systems.
This type of modulator plays a crucial role in modern cable and satellite TV distribution systems, enabling clear and reliable transmission of video and audio signals across a wide range of frequencies.
HDG Radiator
Catering to the ever-changing demands of our patrons, we are offering them a comprehensive range of Hot Dip Galvanized Radiator. These are manufactured as per latest market trends so as to ensure their wide applications in industries. Offered products are highly demanded by the clients for their excellent design, longer service life and durability.
Galvanizing is a way of defending a steel surface from corrosion by delivering a surface coat of Zinc. The process is carried out by dipping the radiator in molten zinc bath which is upheld at a temperature of about 450 degrees.
In long-term, continuous exposure, the recommended maximum temperature for hot-dip galvanized steel is 200 °C (392 °F), according to the American Galvanizers Association. The use of galvanized steel at temperatures above this will result in peeling of the zinc at the inter metallic layer.Hdg Radiator,Oil-Immersed Hdg Radiator,Hot-Dip Galvanizing Radiator,High-Performance Hot Dip Galvanized Radiator
Shenyang Tiantong Electricity Co., Ltd. , https://www.ttradiator.com