What is the difference between a 2.4 GHz remote control and a sub-GHz remote control?
At the same distance, 2.45 GHz gives roughly 15 dB more free-space loss than 433.92 MHz (80.2 dB versus 65.2 dB at 100 m) and, with its 12.2 cm wavelength, attenuates more behind obstacles. In return it offers power up to 20 dBm EIRP under EN 300 328, wide bandwidth and a structure suited to frequency hopping; in sub-GHz the limit is at the 10–25 mW ERP level.
The difference can be reduced to a single number: 20·log10(2450/433,92) = 15,0 dB. With the same transmit power and the same antennas, a 2.4 GHz link starts with a 15 dB disadvantage compared to a 433 MHz link. By the 6 dB rule, that roughly means dropping to a fifth of the range.
But the other items in the link budget can close that gap. The 20 dBm (100 mW) EIRP allowed at 2.4 GHz is about 8 dB higher than the 10 mW ERP limit at 433 MHz. Since the bandwidth is 83.5 MHz, frequency hopping (FHSS) becomes genuinely applicable; a narrowband interference source corrupts only a few hops, the packet is discarded by CRC and retried. Bidirectional acknowledged protocols are easier to build here because channel capacity is plentiful.
In practice:
- Open field, long distance, behind obstacles → sub-GHz is advantageous.
- Short/medium distance, heavy interference, bidirectional acknowledgement and multiple kits working together → 2.4 GHz is advantageous.
On the AXI side, the XRF protocol used by the HCT400 and HCT402 works at 2.4 GHz and uses frequency hopping, bidirectional session verification and a unique pairing ID per device.
Full coverage of the topic: 433 MHz or 2.4 GHz?