Frequency Hopping Spread Spectrum vs Fixed Frequency

Wireless remote controls use either a fixed frequency (FF) or a Frequency Hopping Spread Spectrum (FHSS). A lot of Elsema’s remote controls operate on five frequencies, and customers ask about the benefits of doing this versus using a single frequency.

Fixed Frequency

Fixed frequency remote controls use a single frequency channel to transmit and receive the data. In each region of the world, there are licence free bands (ISM Bands). Licence free band is used by the public and when two or more users in the same area are using the same frequency, the transmissions are corrupted. A corrupted transmission will cause the receiver not to activate when the remote control button is pressed.

Elsema’s PentaFOB® uses frequency hopping spread spectrum (FHSS).

Available in 1, 2, 4 and 5 button configurations.

Frequency Hopping Spread Spectrum

Frequency Hopping Spread Spectrum (FHSS) does exactly what its name implies – the carrier will automatically change to hop from frequency to frequency. This will allow the transmission to occur over several frequencies. This results in the data to tolerate a significant amount of in-band interference providing that it affects only part of the spectrum. In general, if 1, 2 or even 3 frequencies are interfered in a 5 frequency hopping system it will still operate at its full operating range.

Since each FHSS remote control has its own frequencies and hop sequence. The chances of two remotes on the same frequency is greatly reduced. In the event of a hop clash, those remote messages are corrupted, however the probability that both remotes will hop to the same frequency a second time is very low. Therefore, a FHSS remote control system is more immune to interference when compared to a single or fixed frequency remote control system.

Elsema’s latest PentaFOB® and PentaCODE® keyring remotes use Frequency Hopping Spread Spectrum (FHSS) technology.

The left diagram shows a spectrum analyser of a fixed frequency (FF) and the right diagram shows 5 frequencies hopping over a time domain (FHSS).

Frequency Hopping Spread Spectrum
Frequency Hopping Spread Spectrum

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