1500W FM Harmonic Absorbing Low Pass Filter

All RF amplifiers will "react" in some way when a low pass filter is attached. This reaction is mainly caused by reflected harmonics. All RF amplifers generate harmonics. When a low pass filter is attached to the amplifer most of the harmonic energy is reflected back to the transistor causing reduced efficency and output power. The transistor will also run hotter.

The new LDMOS transistors have higher gain at high frequencies ; therefore, they are more sensitive to the reflections from the low pass filter. For this reason we have developed a state of the art low pass filter to match the state of the art transistors. This filter terminates all harmonics up to 550MHz with a 50 ohm 250W termination. This filter will improve the performance of all FM amplifiers.

This low pass filter is designed for use with the BLF574 600W, BLF178P 900W and BLF178XR 900W FM Pallets only; however, our standard low pass filters also work well.

Technical specifications:

• Silver Plated #8 AWG inductors.
• Teflon circuit board.
• 0.1dB Insertion loss typical.
• 30dB Return loss typical in FM Band 87.5 to 108MHz
• 1/4 inch aluminum base.
• 3 inch x 6 inch size.
• -10dB return loss typical 176 - 550MHz in harmonic terminated side.
• download connection diagram
• Download mechanical drawing in DXF file format