Helical Bandpass Filter Frequency RF Custom Frequency Options 340MHz

Helical Bandpass Filter Frequency RF Custom Frequency Options 340MHz

Helical filters are a critical component in modern RF and microwave systems, providing selective frequency filtering with excellent performance in terms of insertion loss, rejection, and stability. The Helical Bandpass Filter (336MHz–344MHz) is designed for high-performance applications where precise frequency control and signal purity are essential. With its robust design, low loss, and high rejection characteristics, this filter is widely used in communication systems, broadcasting equipment, military radio, and various wireless transmission solutions.

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Product Overview

The Helical Bandpass Filter is a compact and reliable RF filter specifically tuned to operate within the 336MHz to 344MHz frequency range. It is engineered to allow only the desired signals within this band to pass while effectively attenuating unwanted frequencies outside the range. Built with high-quality materials and advanced helical resonator technology, this filter delivers superior electrical performance in demanding environments.

This model offers flexibility for customization, as frequencies can be adjusted according to customer requirements. Whether for OEM integration, system upgrades, or specialized communication equipment, the filter provides an ideal solution to ensure stable, clean, and interference-free signal transmission.

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Key Specifications

Standard Parameters

Item	Specification
Frequency Range (Passband)	336 MHz – 344 MHz
Other Frequency Options	Customizable to customer demand
Insertion Loss	≤ 1.2 dB
Passband Ripple	≤ 0.5 dB
Return Loss	≥ 15 dB
Out-of-Band Rejection	≥ 40 dB @ Fo ± 50 MHz
Power Handling	≤ 10 W
Impedance	50 Ω
Connector Type	N-KFD (RF connector)
Module Size (mm)	89 × 20 × 32 (excluding joints)

Customizable Parameters

Item	Specification (337–343 MHz Band)	Specification (520–524 MHz Band)
Operating Frequency	337–343 MHz	520–524 MHz
Insertion Loss	≤ 2.4 dB	≤ 1.2 dB
Return Loss	≥ 15 dB	≥ 15 dB
VSWR	≤ 1.3	≤ 1.3
Out-of-Band Rejection	≥ 20 dB @ 328 MHz≥ 20 dB @ 352 MHz	≥ 40 dB @ 460 MHz≥ 40 dB @ 590 MHz
Power Handling	10 W	10 W
Connector	N-Male / N-Female	N-K / N-J
Dimensions	101 × 26 × 22 mm (including bracket)	89 × 32 × 20 mm

Helical Bandpass Filter Frequency RF Custom Frequency dimension

520-522-524MHz Helical Bandpass Filter

337-340-343MHz Helical Bandpass Filter

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Detailed Feature Breakdown

1. Frequency Selectivity

The filter has been optimized to operate in the 336–344 MHz band, providing precise bandpass characteristics. This narrowband design ensures that only signals within this range are passed, making it particularly useful in communication links that require high spectral efficiency.

2. Low Insertion Loss

With an insertion loss of ≤1.2 dB, this filter ensures that the signal strength within the passband is preserved, minimizing degradation during transmission. This low loss makes the product suitable for sensitive receiver front ends, where every decibel of signal strength is critical.

3. Stable Passband Performance

The passband ripple of ≤0.5 dB guarantees a smooth and uniform transmission across the entire band. This reduces distortion and maintains the integrity of transmitted signals, which is vital for applications requiring high signal fidelity such as digital communication and video transmission.

4. High Out-of-Band Rejection

The filter achieves ≥40 dB rejection at Fo ± 50 MHz, ensuring effective suppression of nearby interference sources. This level of rejection is essential in dense RF environments, preventing adjacent channel interference and enhancing overall system performance.

5. Return Loss and Impedance Matching

A return loss ≥15 dB confirms excellent impedance matching, minimizing signal reflection and maximizing power transfer. With a standard 50 Ω impedance, the filter integrates seamlessly with most RF systems, transmitters, and receivers.

6. Power Handling Capability

Designed with durability in mind, the filter supports a power rating of ≤10W, making it suitable for both low and medium power RF systems. This ensures reliable performance even in transmission applications that demand higher signal strength.

7. Mechanical Design and Connectors

The filter is built in a compact housing (89 × 20 × 32 mm, excluding connectors) for easy integration into space-constrained systems. It features an N-KFD connector, known for its durability and reliable RF performance, ensuring secure connectivity.

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Applications

The Helical Bandpass Filter (336–344MHz) finds broad applications across multiple industries:

1. Wireless Communication Systems

   • Used in base stations, repeaters, and transceivers to filter out unwanted signals.

   • Ensures clear and interference-free communication in mobile and fixed networks.

2. Military and Defense

   • Integral for secure and robust tactical communication systems.

   • Provides precise channel separation in radio communications during missions.

3. Public Safety Networks

   • Supports police, fire, and emergency response communication systems.

   • Guarantees reliable communication without interference, especially in crowded spectrum environments.

4. Broadcasting Equipment

   • Used in FM and VHF broadcasting stations.

   • Improves signal clarity and transmission quality for both audio and video signals.

5. Test and Measurement Systems

   • Incorporated into RF testing equipment for accurate signal analysis.

   • Filters unwanted frequencies to ensure reliable test measurements.

6. UAVs and Drone Applications

   • Helps maintain clean downlink and uplink signals for video and telemetry systems.

   • Supports COFDM-based wireless image transmission systems where stable signals are essential.

7. Industrial and Research Applications

   • Utilized in laboratory RF setups and industrial wireless monitoring systems.

   • Supports research experiments requiring precision filtering at VHF frequencies.

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Advantages of Helical Filter Design

The helical filter architecture provides several distinct advantages compared to traditional LC or cavity filters:

1. Compact Size: Despite its high performance, the filter is physically small, making it suitable for modern compact devices.

2. High Q-Factor: Helical resonators offer excellent selectivity and sharp band edges, enhancing overall filter performance.

3. Mechanical Robustness: The design ensures stable performance even under vibration or temperature fluctuations.

4. Scalability: Frequencies can be easily tailored to customer requirements without significant redesign.

5. Superior Rejection: Provides higher out-of-band rejection compared to many alternative filter technologies.

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Customization Options

Recognizing that every application has unique frequency requirements, we offer customizable designs. While the standard model covers the 336–344 MHz band, the filter can be tuned to other frequency bands upon request. Engineers can specify:

• Center frequency

• Bandwidth

• Connector types (N-type, SMA, etc.)

• Housing size constraints

This flexibility makes the filter highly adaptable across industries and project-specific needs.

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Reliability and Quality Assurance

Each Helical Bandpass Filter undergoes rigorous quality control and performance testing to ensure compliance with specifications. Parameters such as insertion loss, return loss, and rejection are measured with high-precision network analyzers. The housing is manufactured from durable materials to withstand long-term use in both laboratory and field conditions.

Additionally, the product is designed to comply with international RF component standards, ensuring compatibility with global markets.

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Integration and Installation

The filter’s N-KFD connectors make installation simple and secure, allowing fast integration into existing systems. Its 50 Ω impedance ensures seamless compatibility with most RF transmission and reception equipment. Due to its small form factor, the filter can be installed in both portable and fixed communication setups without occupying significant space.

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Example Use Case

Consider a public safety communication network operating around 340 MHz. In such a scenario, multiple agencies share nearby frequency bands, creating the risk of interference. By incorporating this 336–344 MHz Helical Bandpass Filter into the system, engineers can ensure that only the intended signals are received while rejecting out-of-band interference. This results in improved clarity, reduced noise, and enhanced reliability for mission-critical communications.

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Conclusion

The Helical Bandpass Filter (336MHz–344MHz) is a high-performance RF component that delivers precision filtering, low insertion loss, and excellent out-of-band rejection. Its compact design, customizable frequency options, and robust construction make it suitable for a wide variety of applications, from defense communication to UAV systems. By ensuring clean and stable signals, this filter significantly enhances the performance of modern wireless communication systems.

Whether deployed in broadcasting, tactical communication, or industrial monitoring, this filter provides the reliability and efficiency required in today’s demanding RF environments. With customization options available, it is a versatile solution that can be tailored to meet the unique requirements of any project.

FAQ

Questions: What frequency at edge?

Answer: 330-350MHz. We also offer customization options. To avoid fluctuations caused by temperature changes, the frequency range is occasionally broadened.

Question: What will be the rejection at ±12 MHz from the center frequency of the custom helical filter?

Answer: According to software simulation results, the rejection (suppression) at ±12 MHz offset is approximately 10 dB to 12 dB.

Question: What is the maximum power handling capacity of the helical filter?

Answer: The standard helical filter can handle up to 5 W CW (continuous wave) power. This rating meets the requirements of most COFDM and FPV video transmission systems.

Question: Can the helical filter support higher power levels, such as 10 W?

Answer: Yes. A custom high-power version is available upon request. With larger housing, enhanced thermal design, or silver-plated conductors, the filter can handle up to 10 W CW.

Question: How should I choose between 5 W and 10 W versions?

Answer: If your transmitter output power is below 5 W, the standard model is sufficient. For transmitters with output power close to or above 5 W, we recommend choosing the 10 W custom version for safe operation and longer lifespan.

Question: Does higher power handling affect the filter’s performance?

Answer: No significant difference in filtering characteristics. However, high-power filters are slightly larger in size and may have lower insertion loss due to improved conductor quality.

Question: Can you customize the filter according to my system power and frequency?

Answer: Yes, both center frequency and power handling can be customized. Please provide your required frequency band and output power so we can design a suitable model.

Question: What is the rejection at 377 MHz and insertion loss at 340 MHz?

Answer: Please refer to the test results below for detailed measurement data.

Question: Loss is 2.2 db at 340 mhz right?

Answer: If you want to minimize insertion loss, the suppression will worsen. The filter has been designed with an additional cavity, which slightly increases the insertion loss but improves the out-of-band rejection performance.