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Converting CC1020EMX-868 to -433

Other Parts Discussed in Thread: CC1070, CC1020

Hi,

My client sends a locating signal at 433MHz using a CC1070 and is able to locate the transmitter using a handheld receiver. The transmitter also sends identifying data in UART format and now wants to receive and display the transmitter ID.

I have purchased a CC1020/1070DK development kit, but could only get the -868MHz version. I have done a BOM comparison between the -868 and -433 variants, and used SmartRF Studio with the target frequency, to identify the component changes required to convert the -868 to -433 and have made those changes to both CC1020EMX modules. But with a working transmitter, and the CC1020EB with CC1020EMX operating using SmartRF Studio, I'm getting -122dB of RSSI.

Has anyone here done a -868 to -433 conversion on this development kit? Does anyone have any advice on how I could proceed to debug this setup?

  • -122 dBm is what I would expect if you measured RSSI using the minimum RX filter BW and no signal applied at the antenna. Seems like you have a transmitter and still measure -122 dBm. First thing to check is if there is a significant frequency offset between the transmit and receive units. Simplest way of doing this is to set the modified 433 MHz unit into TX and measure the frequency offset (set the deviation to 0 in this test, otherwise you will measure carrier+deviation (or carrier - deviation; don't recall exactly))
  • Thank you for your suggestion. Putting the module in Tx mode gives a PLL lock (lock bit = 0). I don't have a spectrum analyser, but I do have a scanner. The scanner detects the client's transmitter at the correct frequency, but I can find no carrier at all from the CC1020 module, over the whole 433 or 868 ranges. For a £500 development kit, the technical information contained is woeful, (the CD doesn't even read correctly). So any further suggestions would be very welcome.