All of our remote control transmitters developed for customers are unlicensed remote control devices, and need to comply FCC rules Part 15, which governs the operation of unlicensed devices and is designed to facilitate their use while preventing interference to licensed operations, so operation of unlicensed devices is subject to following conditions.
Unlicensed devices may not cause harmful interference, and unlicensed devices must accept any interference received, including interference that may cause undesired operation.
And there are two types of remote control devices that falls into FCC Part 15, the first is most medium range devices that works under 250m, the transmitting power is usually limited to 10dB maximum, with operating frequency usually at 315 – 433Mhz, and is governed by FCC 15.249, the second type is long range remote control devices that can work as long as 3000m, the transmitting power can reach max. 30dB, the transmitting frequency is usually at 902 – 928 Mhz in sub-Ghz range, and is governed by FCC rules 15.247.
To maintain maximum 30dB transmitting power, FCC 15.247 requires transmitter to use frequency hopping technique, and employing at least 50 hopping channels, the hopping should be pseudo randomly distributed so the interference chance will be minimized, the details of frequency hopping systems can be found at following.
Frequency hopping systems shall have hopping channel carrier frequencies separated by minimum of 25kHz or the 20dB bandwidth of the hopping channel, whichever is greater.
Frequency hopping systems in the 2400 – 2483.5 MHz frequency band may have hopping channel carrier frequencies that are separated by 25kHz or two thirds of the 20dB bandwidth of the hopping channel, whichever is greater, provided the systems operate with an output power no greater than 125 mW.
Frequency hopping systems shall hop to channel frequencies that are selected at the system hopping rate from a pseudo randomly ordered list of hopping frequencies. System receivers shall have input bandwidths that match the hopping channel bandwidths of their corresponding transmitters and shall shift frequencies in synchronization with the transmitted signals.
The incorporation of intelligence within a frequency hopping spread spectrum system that permits the system to recognize other users within the spectrum band so that it individually and independently chooses and adapts its hopsets to avoid hopping on occupied channels is permitted. The coordination of frequency hopping systems in any other manner for the express purpose of avoiding the simultaneous occupancy of individual hopping frequencies by multiple transmitters is not permitted.
Frequency hopping spread spectrum systems are not required to employ all available hopping channels during each transmission. However, the system, consisting of both the transmitter and the receiver, must be designed to comply with all of the regulations in section 15.247 should the transmitter be presented with a continuous data (or information) stream. In addition, a system employing short transmission bursts must comply with the definition of a frequency hopping system and must distribute its transmissions over the minimum number of hopping channels specified in this section.
Hopping frequencies, channel bandwidths and max allowed output power can be found at the table below.
|Frequency Band||Hopping Frequencies||Max Allowed 20dB Bandwidth of Hopping Channel||Max Peak Conducted Output Power|
|902 – 928 Mhz||If the 20dB bandwidth of the hopping channel is less than 250kHz: Use at least 50 hopping frequencies, avg. time of occupancy on any frequency shall not be greater than 0.4s within a 20s period.If the 20dB bandwidth of the hopping channel is greater than 250kHz: Use at least 25 hopping frequencies, avg. time of occupancy on any frequency shall not be greater than 0.4s within a 10s period||500 kHz||For systems employing at least 50 hopping channels: 1 Watt or 30dBmFor systems employing less than 50 hopping channels but at least 25 hopping channels: 0.25 Watt or ~23.97dBm|
|2400 – 2483.5 Mhz||Use at least 15 channels, avg. time of occupancy on any channel shall not be greater than 0.4s within a period of 0.4s multiplied by the number of hopping channels employed||May avoid to suppress transmissions on a particular hopping frequency provided that a min. of 15 channels are employed||For systems employing at least 75 non-overlapping hopping channels: 1 Watt or 30dBmFor all other systems: 0.125 Watt or ~20.96dBm|
|5725 – 5850 Mhz||Use at least 75 hopping frequencies, avg. time of occupancy on any frequency shall not be greater than 0.4s within a 30s period||1 Mhz||1 Watt or 30dBm|
Note: the maximum peak conducted output power is valid when use antennas with directional gains that do not exceed 6dBi
We would recommend using 902 – 928 Mhz frequency if customers needs long range remote control transmitter that works in 250 – 3000m range, the hopping frequency technique also increases overall operation stability by minimizing the chance being interfered by other narrow band transmitting devices working in this frequency range.