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Re: OT3m with Nuvi 350

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  • Mads
    Just a little update. As some of you suggested that the PX-777 might cause the problem I replaced it with an old Motorola MC Micro. Here s the result: Nuvi 350
    Message 1 of 19 , Feb 2, 2012
      Just a little update. As some of you suggested that the PX-777 might cause the problem I replaced it with an old Motorola MC Micro. Here's the result:

      Nuvi 350 + OT3m + PX-777 = Not decoding packets
      Nuvi 350 + OT2m + PX-777 = Working fine!

      Nuvi 350 + OT3m + Motorola MC Micro = Not decoding packets
      Nuvi 350 + OT2m + Motorola MC Micro = Working fine!

      On the PX-777 I've tried squelch off and Software DCD on and squelch on (lvl 1) and software DCD off.

      Any more suggestions? I can post the DISPLAY text if needed.

      73! Mads, LA1TPA


      --- In tracker2@yahoogroups.com, "Mads" <la1tpa.qrp@...> wrote:
      >
      > Hello all
      >
      > It seems like my two brand new OT3m's won't decode packets.
      >
      > I have a Puxing PX-777 and a Garmin Nuvi 350 connected to the tracker. I can send packets successfully but not receive any!
      > When I replace the OT3m with my old OT2m everything works fine. Please help!
      >
      > 73! Mads, LA1TPA
      >
    • Scott Miller
      Any chance you ve got an oscilloscope to check what the audio level is? I can walk you through checking a few places if you d like. The trackers are all
      Message 2 of 19 , Feb 2, 2012
        Any chance you've got an oscilloscope to check what the audio level is?
        I can walk you through checking a few places if you'd like. The
        trackers are all tested for RX before they leave, but it's always
        possible a solder joint failed or something.

        Scott

        On 2/2/2012 12:28 AM, Mads wrote:
        > Well, the FCS count actually increased to 4 after a few hours.
        >
        > 73! Mads, la1tpa
        >
        > --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
        > Scott Miller <scott@...> wrote:
        > >
        > > Then it's probably not getting any audio. Do you have another tracker
        > > or TNC that you can use to verify your cabling?
        > >
        > > Scott
        >
        >
      • Mads
        Actually I have an old oscilloscope collecting dust in the basement. It should be suitable for AF measurements. Please provide some (detailed) instructions on
        Message 3 of 19 , Feb 2, 2012
          Actually I have an old oscilloscope collecting dust in the basement. It should be suitable for AF measurements. Please provide some (detailed) instructions on where to measure to the e-mail address on my qrz.com profile.

          73! Mads, la1tpa

          --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
          >
          > Any chance you've got an oscilloscope to check what the audio level is?
          > I can walk you through checking a few places if you'd like. The
          > trackers are all tested for RX before they leave, but it's always
          > possible a solder joint failed or something.
          >
          > Scott
        • Scott Miller
          I m going to post this here so it s in the group archive. This applies to PCB v1.1 (note that there s a stray v1.0 marking in the lower left of the board - I
          Message 4 of 19 , Feb 7, 2012
            I'm going to post this here so it's in the group archive. This applies
            to PCB v1.1 (note that there's a stray v1.0 marking in the lower left of
            the board - I only recently discovered that.)

            The RX section is in the upper left of the board, near the radio DB9
            connector. You should see the input signal at ferrite chip L4 (left of
            D5, not marked). C2 and/or C18 (depending on whether SJ2 is set) AC
            couple the signal to the op amp input. You should see the op amp input
            on the left side of R2. You'll see the output at R9, which connects by
            a fat trace to the ADC input on the microcontroller. The entire audio
            path stays on the top layer of the PCB, and it's pretty visible because
            the traces are wider than anything but the power traces.

            Some problems I've seen that prevent RX from working are bad solder
            joints on components in that section, an improper value for C11 (should
            be 22pF, can be removed without any real impact), and an improper value
            for either R8 or R11 (both should be 30k and the voltage at their center
            point should be 1/2 Vcc).

            Scott

            On 2/2/2012 10:29 AM, Mads wrote:
            > Actually I have an old oscilloscope collecting dust in the basement. It
            > should be suitable for AF measurements. Please provide some (detailed)
            > instructions on where to measure to the e-mail address on my qrz.com
            > profile.
            >
            > 73! Mads, la1tpa
            >
            > --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
            > Scott Miller <scott@...> wrote:
            > >
            > > Any chance you've got an oscilloscope to check what the audio level is?
            > > I can walk you through checking a few places if you'd like. The
            > > trackers are all tested for RX before they leave, but it's always
            > > possible a solder joint failed or something.
            > >
            > > Scott
            >
            >
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