Maximum out-of-band input power to JN3/SL868

6 thoughts on “Maximum out-of-band input power to JN3/SL868

  1. Hello

     

    Can anybody say how much out-of-band input power (especially at 2,4GHz) is allowed to the RF-input of the JN3 Module?I didn’t see anything in the pdf’s.

    I have a ISM RF-module which shares the same antenna cable via an antenna splitter but i need to know how sharp the frequency separation of the splitter/filter have to be.

    it’s ok if the JN3 receiver do not work in when the RF Module is on TX but it should not be destroyed.

     

    Thanks

    1. Hi Oliver,

       

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      Rather than using a power splitter, you should use a diplexer. You won’t have the RF losses of the power splitter, and will get additional isolation between 2.4 GHz and GPS.
       
      While we specify the maximum RF level into the JN3 as +10 dBm, that number is only specified to 2 GHz maximum.
       
      Depending upon how bad the out of band noise is, it could jam the receiver by capturing the LNA even in the case of JN3. We tried running RF susceptibility tests on the JN3 and could not get past the broadband noise coming from the TWT power amplifier.

  2. Hi All

     

    Should the EXT_INT on the JN3 be driven low as per waveform diagrams in the datasheet or should I configure as an input on my micro as a high impedance input as suggested in the datasheet text?

     

    I have a problem where JN-3 stops tracking satellies for some reason and only a power cycle seesm to fix it?

     

    Regards

    Gavin 

    1. Hi Gavin,

       

      which firmware version are you using on your JN-3?

       

      Could you please send me a log before and after power cycle?

       

      Regards

       

       

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        This is MID 41 message prior to reset.

        We have about 1500 devices in the field so can’t log all GPS strings waitng for one to enter this state as I would be accumulating Gig’s of info per device.

         

        Firmware Version: GSD4E_4.1.0_CCK_OSP

         

        MID = 0x29 (Dec 41)

         

        29

        00 01 – Not overdetermined

        00 00 – No Lock

        06 B7  – week number

        02 5C 42 EE  – TOW

        00 00 00 00 00 00 00 00 -UTC

        00 00 00 00 – Satellite ID list

        F0 59 C8 F1  – Latitude

        10 B8 81 B2  – Longitude

        00 02 67  E9 – altitude elipsoid

        00 02 67 E9  – altitude MSL

        15 – Datum WGS-84

        00 00 – SOG

        00 00  – COG

        00 00 – Magnetic variation

        00 00 – Climb rate

        00 00 – heading rate

        00 00 00 00  – EHPE

        00 00 00 00  – EVPE

        00 00 00 – ETE

        00 00 – EHVE

        55 3E 62 EC – Clock BIAS

        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
        – rest are zero’s

        1. Hi Gavin,

           

          a log file of maybe a few units will help. Maybe it could be releated to a not good rf environment.

           

          Thanks in advance.