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Tracker3 - Foxtrack interoperability

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  • owenvk
    I have been playing with a T3-135 and I cannot get it to decode packets from a Foxtrak (well two Foxtraks in fact). The Foxtrak is decoded by some other
    Message 1 of 4 , Aug 1, 2014
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      I have been playing with a T3-135 and I cannot get it to decode packets from a Foxtrak (well two Foxtraks in fact).

      The Foxtrak is decoded by some other devices, but not the T3-135 or OT-USB.

      Have others encountered this problem, and perhaps have a solution?

      Owen


    • Scott Miller
      Is the Foxtrak transmitting flat or with pre-emphasis, and do you know what the deviation level is? Scott
      Message 2 of 4 , Aug 1, 2014
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        Is the Foxtrak transmitting flat or with pre-emphasis, and do you know
        what the deviation level is?

        Scott

        On 8/1/2014 10:14 AM, owenvk@... [tracker2] wrote:
        >
        > I have been playing with a T3-135 and I cannot get it to decode
        > packets from a Foxtrak (well two Foxtraks in fact).
        >
        > The Foxtrak is decoded by some other devices, but not the T3-135 or
        > OT-USB.
        >
        > Have others encountered this problem, and perhaps have a solution?
        >
        > Owen
        >
        >
        >
      • owenvk
        Here is the status of the DR-135 + T3-135 at this moment: the system s tx audio was too high (adjusted before any testing for 3kHz devn at 2200Hz); the tx
        Message 3 of 4 , Aug 1, 2014
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          Here is the status of the DR-135 + T3-135 at this moment:
          1. the system's tx audio was too high (adjusted before any testing for 3kHz devn at 2200Hz);
          2. the tx signal is lacking pre-emphasis;
          3. it is likely that the rx path does not de-emphasise;
          4. the rx never decodes the Foxtrak;
          5. it repeats VK2RHR-1 (OT3m), VK2AMW-1 (unknown), and my OT-USB and TNC-X packets.


          With the Foxtrak, I have tried different modulation levels, different freq cal constants, tx de-emphasis to nullify tx pre-emphasis, and original Byonics TT firmware.

          The Foxtrak is decoded by VK2AMW-1 (unknown modem), VK2OMD-3 (TNC-X), my VK6 modem (AM7910), but NEVER by the OT3 or VK2RHR-1 (OT3m).


          I have done a drive test with my Foxtrak, and it is never repeated by VK2RHR-1 (OT3m), nor was my friend's Foxtrak when he drove through the area a few days ago.Both stations are repeated by VK2AMW (unknown) and VK2OMD-3 (TNC-X and AM7910 tested).

          I understand that the Foxtrak tones are more than 10Hz off which I suspect breaches Bell202, lets call the Foxtrak/TT scheme Ham202.

          Nevertheless, other modems decode 'Ham202'.

          Can you confirm my measurement that the tx is not pre-emphasised, and suspicion that the tx path is not de-emphasised.

          Any thoughts?



          Owen
        • owenvk
          Some further information... I looked at the piecewise sine wave at the junction of R8 and R12 in my Foxtrack. The 1200Hz waveform looked fine, but there was
          Message 4 of 4 , Aug 2, 2014
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            Some further information...

            I looked at the piecewise sine wave at the junction of R8 and R12 in my Foxtrack.

            The 1200Hz waveform looked fine, but there was substantial jitter on the 2200Hz waveform which I expect will broaden its spectral response somewhat.

            The video at FoxTrak2kHz

             

            shows the effect.

            I don't know if this contributes to the interoperability problem I experience. I cannot do the same test with TT1 firmware as I don't think it can send a steady tone.

            Owen
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