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CC1120: Sniff mode (smart preamble) and FCC 15.247

Jose Carballo
Prodigy 10 points
Part Number: CC1120

Hi,

We have had a product for many years based on this transceiver that works on batteries (low consumption is critical) and that is why we use the sniff mode.
Currently we need to certify FCC for Australia and therefore the certification laboratory recommends us to use FHSS or, as a last resort, drastically lower the transmission power.

My question is if there is any configuration for this transceiver that can meet the FCC requirements, without using FHSS or lowering the transmission power.

If it does not exist, could it be possible to continue using the sniff mode in a fixed channel as up to now and when establishing a communication, enable the FHSS?

The current configuration is 915MHz, 2-GFSk, 50kbps, dev 25khz and BW 100KHz.

Regards and thanks in advance

José

  • 0
    Mastermind 6470 points

    You either has to comply with FCC 15.249 (low output power) or FCC 15.247 (high output power but you either have to do frequency hopping or occupy a 500 kHz BW). The latter is not possible with 50 kbps. Meaning that you either have to live with ~-1 dBm output power or frequency hopping. The latter may work with a rewrite of the code. I believe it's a limitation of how often you can be on each channel meaning that you can only send a few smart preamble packets pr channel. It depends how you want to implement frequency hopping, if you have a time stamp you can start listing to the correct channel but I would assume that you will end up having to be in RX too long.

    This is not a chip thing, more a understanding the FCC requirements.