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Sub 1GHz programming

Other Parts Discussed in Thread: SIMPLICITI

I've designed various Bluetooth products in the past but have never worked with sub 1Ghz.  I have a client that needs a product that can transmit a 2-digit ID over a distance of 200 meters.  The product will be sold globally.  I'm leaning toward 2.4GHz because it is global but I worry about the 200 meter range.  868/915/920 Mhz would offer better range but adds the complication of using different frequencies for different countries.  Also I've never programmed a proprietary RF transceiver.  How complex woud it be to program this application?  Do you think 868/915/920 MHz is a better solution than 2.4GHz for this application?

Thanks,

John

  • For world wide look into 433 MHz.  This is a band that is available in most countries.

    For 200 m range (I would assume that this is not line of sight) and indoors use I would look for sub 1 GHz. Take a look at the excel sheet in this post:

    The complexity of programming depends on which protocol you would like to use. If the purpose is just to send 2 byte (Tx only) the programming is fairly simple.

  • I thought 433 Mhz was reserved for licensed HAM operators in the U.S., unless the power is extremely low. Can enough power be used in the U.S. at 433Mhz to reach the desired range?
  • Depends on how complex the system is and if indoors or outdoors: if it's just a point-to-point system with little data and where transmitter must reach the receiver directly without range extenders; forget 2.4 GHz and go as low as you can in frequency. If system shall be used indoors, forget both 868 or 915. Why not try 27 MHz shortwave? Simple, works globally and have the range.
  • 15.231(a) is for simple control signal, like an alarm system, door opener, or a remote switch. @433 MHz the output power is -14.4 + 20*log(100 ms/TX_on_time) [max 5.6 dBm], where TX_on_time is the maximum transmission time in any 100 ms period.

    For applications that do not meet the restrictions of 15.231(a), lower transmit signal levels are given in 15.231(e). @433 MHz the output power is -22.4 + 20*log(TX_on_time/100ms) [max -2.4 dBm], where TX_on_time is the maximum transmission time in any 100 ms period. According to 15.231(e) the duration of one transmission shall be shorter than 1 second and the off time between transmission shall be at least 30 times the duration of the transmission or 10 seconds, whichever is greater. Example: If the transmission time is 10 ms (or less) the output power @433 MHz is -2.4 dBm and you can have 6 transmission per minute.
  • 27 MHz is usually not a frequency that you would consider. The antenna efficiency will be poor and large in size. If you look at the radio products offered by the main players in the sub-1 GHz ISM/SRD space you will see that the focus is on 169/433/868/915 MHz.
  • hello 

    I am using chronos watch as a target device(link to)  and my own prototype board (cc430f6137) as two end device( link listen).

    but i couldnt communicate these two links. i am using the the same schematic and components which is in the watch as given in the datasheet.

    Kindly help me 

  • Hi Prakash,
    Did you tried to link two Ez430 chronos watches ?
  • I didnt try that. But i thing i order to do that, simpliciti for chrous watch and simpliciti for cc430em should be embed. i am working on it
  • hello

    i tested with two ez430 chronos watch also. i can commuicate with each other.
    i can communicate within my own prototype boards also using simpliciTi V1.2.0 by link to and link listen program.

    but i coudnt communicate with Chronous watch as(link to) and my own board as (link listen). couldnt find where i am making mistake.

    In my own prototype board i didnt fix ACLK 32khz .. i guess it may be one of my problem.

    Kindly help me.