Resolving frequency conflicts

[Guenther]

I am a total "Newbie" to RF communication so I would welcome some guidance WRT to how multiple PTX/RTX devices in a given locale are commonly handled. I intend to employ the nRF24L01+ devices for remotely controlling a electric trolling motor. I am aware of using device addresses to ease this issue but how would one resolve two "systems" (PTX RTX pair) powering up to the same frequency. Frequency Hopping using a predefined algorithm with a common "seed" for next frequency is the only solution that I am able to envision. If anyone is able to tolerate this "Newbie" topic please advise of workable solutions or point me to a White Paper.

Many Thanks and Best Regards Guenther

[Øyvind Karlsen]

Hi Guenther,

Note that my examples might not be directly related to the nRF24, but aim to give a general idea of how this is commonly done in RF systems. Some common ways of addressing this issue are:

Use different channels for each pair

As an example, a cheap walkie-talkie will have a channel switch that will let you select between, say 8, channels. All your walkie-talkies on channel 1 will be able to hear, and send information to each other. The compromise is that now you cannot use all your channels for data, this might be fine if your datarate is low.

Filter by encryption key in your application

A more expensive walkie-talkie might feature some filtering mechanism, for example tone squelch(Tone squelch adds a second lower frequency carrier to your signal and the receiving radio will have to filter for this in addition to the high frequency carrier). Now you could theoretically have two signals on the same channel and still have them be distinguishable, however you might have issues with noise. Have a look at the selectivity specified in the datasheet for the radio you want to use, it gives an idea of how good the radio is at selecting between in-band signals.

Best regards,

Øyvind