The 900 MHz band is part of the UHF (Ultra High Frequency) spectrum and spans 902–928 MHz in the United States. This band is allocated as an ISM (Industrial, Scientific, and Medical) band but is also shared with amateur radio on a secondary basis. Here’s an overview of its role in amateur radio:
Characteristics of the 900 MHz Band
- Propagation:
- The 900 MHz band behaves similarly to other UHF frequencies but offers slightly higher attenuation due to its shorter wavelength.
- Signals are primarily line-of-sight and can penetrate buildings better than higher frequencies like 1.2 GHz but less effectively than VHF.
- Bandwidth:
- The band offers a wide 26 MHz of spectrum, allowing for high-speed data applications, experimentation, and voice communications.
- Shared Use:
- As a shared band, amateur radio operators must avoid interfering with primary users like ISM equipment, which includes devices like cordless phones, Wi-Fi, and industrial systems.
Applications in Amateur Radio
- Repeater Systems:
- 900 MHz is increasingly used for amateur radio repeaters, providing coverage in urban areas. These repeaters often require specialized equipment, as commercial 900 MHz devices may need modification for amateur use.
- Digital Modes:
- Modes such as D-STAR, DMR, and P25 can operate in the 900 MHz range, enabling digital voice and data communication.
- Mesh Networking:
- Amateur radio operators use the 900 MHz band for HSMM (High-Speed Multimedia Mesh) networks, leveraging it for broadband-like applications.
- Experimental Projects:
- The band is popular for experimentation, including SDR (Software-Defined Radio), microwave link tests, and innovative antenna designs.
Equipment for the 900 MHz Band
- Amateur radio equipment for this band is less common than for lower bands like VHF or HF.
- Operators often repurpose commercial gear such as Motorola radios or modify ISM-band transceivers for amateur use.
- SDR platforms like HackRF or BladeRF also support the 900 MHz band, making it accessible for tech-savvy operators.
Challenges and Considerations
- Interference:
- The proliferation of ISM devices in the 900 MHz band can lead to interference, especially in densely populated areas.
- Limited Availability:
- Off-the-shelf amateur radio gear for this band is relatively rare, requiring technical skills to adapt commercial equipment.
- Regulations:
- Amateur radio use in this band is secondary, meaning operators must yield to primary users and comply with specific regulations.
Why Use the 900 MHz Band?
The 900 MHz band provides a unique opportunity for experimentation and communication in areas where lower bands might be congested. Its characteristics make it suitable for both voice and data applications, particularly in urban and suburban environments.
As technology evolves, the 900 MHz band is gaining popularity among amateurs who enjoy the challenge of working with higher frequencies and less conventional equipment.
Association News
IRLP and 900 MHz Repeater: Check out the new page re our connection to the Internet Radio Linking Project, our 900 MHz repeater and associated links.