Which frequency should I use when planning to design a RF (Radio Frequency) product in the United States?
315MHz is primarily used for remote key less entry (RKE) systems and garage door openers. As a result, this frequency is somewhat crowded, increasing the chances for interference. The FCC allowed power is lower than 418MHz or 433MHz and the selection and efficiency of antennas is limited.
* 315MHz is also widely used in Asia countries, such as China.
418MHz is a good frequency to use in the US as it is not very crowded. This gives the least likely chance for interference and therefore the best performance.
* 418MHz has once been widely used in the European countries, but now more and more new products adapt a 433.92MHz frequency.
433.92MHz is primarily used for RKE applications in Europe. It is also a popular frequency for active RFID tags which can have a range of up to 1000 feet. It is not good for use in the US because of the chance of interference from amateur radio and the nearby pager band.
* 433.92MHz is widely used in European Union since it is a license-free frequency in the EU.
868MHz-870MHz is an unlicensed band in Europe. The band is subdivided for different applications, but there are not many restrictions on the type or duration of data. Unlike the 902MHz-928MHz band in the US, there are only 2MHz to support many applications, so the band has become somewhat crowded.
902MHz-928MHz is more versatile than the 260MHz-470MHz band in the US because the FCC has only specified the output power and harmonic levels. There are no restrictions on the type or duration of data that can be sent. This gives the design engineer a great deal of freedom in the possible applications, but also results in the band being more crowded. A disadvantage for cost-sensitive applications is that 900MHz modules are typically more expensive due to the more complex filtering and modulation required for link reliability at these higher frequencies.