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Customization and tuning 117&137MHz Cavity Bandpass Filters

Customization and tuning 117&137MHz Cavity Bandpass Filters


This came from a custom request from an Indian client, We need to provide samples of both frequency bands with 117MHz and 137MHz as usual.

We got a picture:

We need to make it according to the above standards. The tables in the picture and the very strict parameters caused us trouble at first, and we designed many styles.

Let's first understand the use of 117-137MHz Cavity Bandpass Filter

Most countries have an FM broadcast frequency range of 87.5-108 mhz. The 117-137 mhz range does include a portion of the FM broadcast spectrum, particularly in certain countries/regions. This band is reserved primarily for air traffic, so in most places non-air broadcast or communications may not be allowed on this band.

The “117-137MHz Cavity Bandpass Filter” is typically used for VHF Airband applications. The VHF Airband is the radio frequency range used for civil aviation communication, allowing pilots and air traffic controllers to communicate. This specific filter helps to allow certain frequencies within the 117-137MHz range to pass through while attenuating or blocking unwanted frequencies outside of this range, ensuring clearer communication and reducing potential interference.

The final test diagram

In order to satisfy the customer, we will be in the customer's request on the basis of tuning out better parameters.

Final appearance drawing

So we named it a new model: XL-BPF-125M-100W-2N, We made two samples, one is 445*223*700mm (117MHz) in dimension, other one is 445*223*780mm (137MHz) in dimension, with black exterior.

If you also need to customize a special model, please contact us, we will try to meet your requirements to do better.


In VHF Airband applications stems

The importance of the “117-137MHz Cavity ” in VHF Airband applications stems from several reasons:

  1. Safety: Clear and reliable communication between pilots and air traffic controllers is paramount for the safe operation of aircraft. Any interference or miscommunication can lead to potentially dangerous situations in the air and on the ground.
  2. Minimizing Interference: In a busy radio frequency environment, many transmissions occur simultaneously. The filter ensures that only the desired frequencies within the VHF Airband are received, eliminating potential interference from other nearby frequencies.
  3. Optimized Communication: By allowing only the desired frequency range to pass through and attenuating unwanted frequencies, the filter ensures that the communication equipment operates at its optimal performance, ensuring clear transmission and reception of signals.
  4. Bandwidth Management: The specified frequency range (117-137MHz) is a dedicated spectrum for aviation communication. The filter ensures that this bandwidth is used effectively and efficiently, without interference from adjacent channels or other electronic sources.
  5. Protection of Equipment: High-quality filters can also protect sensitive aviation communication equipment from potential damage due to unwanted strong signals or spikes in the frequency.
ham radio duplexer filter

The filter plays a crucial role in ensuring the clarity and reliability of communication in the aviation sector, which is essential for the safe and efficient operation of aircraft. Xinlun as a major manufacturer of radio and communication equipment, We produce various filters for different applications. If you need Filters,Duplexers,Switching Units,Combiners And Rf Power Amplifier Modules & Coaxial Cables & Connectors & Antennas, maybe we can help you, We have been supplying continuously for 10 years.

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