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Re: [tracker2] AHAB

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  • Scott Miller
    ... Digipeater capability is no problem. The T2 doesn t output GPS telemetry over the air in NMEA format - it s too inefficient and makes you choose between
    Message 1 of 9 , Sep 6 12:14 PM
      > -Restricted Digipeat Capability
      > -GPS Telemetry Data in NMEA format
      >
      > I'd like to see all SMT components if possible (weight
      > considerations), but this isn't necessary.

      Digipeater capability is no problem. The T2 doesn't output GPS
      telemetry over the air in NMEA format - it's too inefficient and makes
      you choose between course/speed and altitude in a given packet.

      It supports the standard APRS position format, plus Base91 compressed
      format. It'll still give you course/speed and altitude, plus HDOP and
      number of satellites in use if you need that.

      Also, if you're running in Garmin binary mode, you can get rate-of-climb
      in feet per minute. If someone can send me some sample data with the
      proprietary $PGRMV sentence with some vertical velocity (like from a
      plane) for testing I'll see if I can implement that for NMEA mode as
      well. It'll still only work on Garmins, though.

      The OT2m rev 1.0 (formerly Prototype E) is SMT with the exception of the
      connectors and such. The T2-135 is significantly lighter, but doesn't
      have power control for a cutdown device and would need a 5 volt power
      supply and close attention to radio interfacing since it's only intended
      to be used with the Alinco DR-135T.

      I do have some really small (unpopulated) Tracker2 boards on hand still,
      but they suffered from oscillator problems, and I'm not even sure if
      I've got all of the documentation and parts for those still.

      The T2-135 is available now, and the OT2m (the one in the metal case)
      should be here in another two weeks or so if all goes well. The factory
      just contacted me this morning for clarification on some parts, and
      somehow there was a shortage of voltage regulators, but nothing that
      should slow down production.

      Scott
    • James Ewen
      ... By complete communications subsystem, does that include things outside of the APRS tracker? ... The OT2 will do what you ask, but as others have indicated
      Message 2 of 9 , Sep 6 1:12 PM
        On 9/6/07, jeremydayauburn <dayjerd@...> wrote:

        > Myself and two other students have 1.5 weeks to come up with complete
        > design documentation for our communications subsystem

        By complete communications subsystem, does that include things outside
        of the APRS tracker?

        > The features that we need are:
        >
        > -Restricted Digipeat Capability
        > -GPS Telemetry Data in NMEA format
        >
        > I'd like to see all SMT components if possible (weight
        > considerations), but this isn't necessary.

        The OT2 will do what you ask, but as others have indicated NMEA is
        out. I am assuming that you simply want lat/long/cse/spd/alt data. The
        OT2 will do this.

        One thing that you want to be aware of is that you do NOT want to
        digipeat on 144.390 simplex. Listen on a seperate frequency, and
        downlink onto 144.390. Once your balloon gets a couple thousand feet
        in the air, it will never hear a quiet time on 144.390, and will
        appear to be locked up. Balloon borne trackers need to ignore the
        energy on the channel, and transmit blind. Digipeaters need to listen
        for uplink audio, and at altitude, it can be extremely noisy.

        We sent up a digital camera last month, and are still dealing with the
        aftermath. Our project got featured on digg.com and gizmodo.org. At
        least 6 major papers have featured the story, as well as CBC radio,
        Global Television, and CTV.

        Have a peek at the website for some background information. The BEAR
        site has detailed information about the payload construction, as well
        as telemetry data, etc. The SABLE site has photos and other
        information from that set of launches.

        We are planning on setting an altitude record in October with BEAR-III.

        http://bear.sbszoo.com

        Scott, any chances of an OT2 in a tiny SMT version for balloon flights
        like the OT+ SMT?

        It would be great to have digipeating capability as well as the
        ability to change flight parameters in flight by sending messages to
        the payload.

        We are stuffing the payload inside the balloon to reduce total mass,
        and the OT2 won't fit in the nozzle!

        James
        VE6SRV
      • Scott Miller
        ... I did run a digipeater on 144.39. I think I had QUIET set to 0, though, so it ll ignore the fact that the channel is busy. SWDCD should be ON. I was
        Message 3 of 9 , Sep 6 1:25 PM
          > One thing that you want to be aware of is that you do NOT want to
          > digipeat on 144.390 simplex. Listen on a seperate frequency, and
          > downlink onto 144.390. Once your balloon gets a couple thousand feet
          > in the air, it will never hear a quiet time on 144.390, and will
          > appear to be locked up. Balloon borne trackers need to ignore the

          I did run a digipeater on 144.39. I think I had QUIET set to 0, though,
          so it'll ignore the fact that the channel is busy. SWDCD should be ON.
          I was using a non-standard alias, of course - don't want to digipeat
          all of southern California and Nevada's WIDEn-N traffic!

          > Scott, any chances of an OT2 in a tiny SMT version for balloon flights
          > like the OT+ SMT?

          I was thinking of an OT1+ with integrated Copernicus GPS engine and 500
          mW transmitter. (Wasn't I talking to you about that the other day,
          James?) If and when I get a compact transceiver an all-in-one T2 would
          be a possibility. In fact, I'm doing that with the more expensive
          commercial 6-watt RF boards.

          The big problem with a tiny T2 board is that the demand's not really
          high enough to warrant automated production, and the part count is
          enough to make it a pain to produce in-house.

          Scott
        • Jeremy Day
          I guess I should clear up a few things: I meant that the GPS input would be NMEA protocol. Output from the TNC to the radio is (I assume) AX.25 standard. Also,
          Message 4 of 9 , Sep 6 1:34 PM
            I guess I should clear up a few things:

            I meant that the GPS input would be NMEA protocol. Output from
            the TNC to the radio is (I assume) AX.25 standard.

            Also, by restricted digipeat capability, I mean having the digipeater
            listen only for packets from our chase vehicles, which would (I hope)
            be the only packets on whatever frequency we chose. This frequency
            should be different from the national APRS frequency.

            Thanks to everyone for their input.

            Jeremy Day
            Communications Lead
            Auburn High Altitude Balloon Team
            space.auburn.edu
          • Scott Miller
            Ok. NMEA input is fine, of course. As I mentioned, Garmin binary mode will give you vertical speed, but you ll also get estimated position error rather than
            Message 5 of 9 , Sep 6 1:53 PM
              Ok. NMEA input is fine, of course. As I mentioned, Garmin binary mode
              will give you vertical speed, but you'll also get estimated position
              error rather than HDOP, and time will be off a bit due to the lack of
              leap second handling in the current firmware.

              You can restrict digipeating by using a non-standard alias. I think I
              used AIR for mine. You just need to set the path appropriately on the
              stations using it.

              And to clarify further on the NMEA thing, all APRS output is going to be
              AX.25 (well, unless you're running PSK31 anyway) - but APRS lets you use
              NMEA or one of three or four other position formats within that AX.25
              packet.

              Scott

              Jeremy Day wrote:
              >
              >
              > I guess I should clear up a few things:
              >
              > I meant that the GPS input would be NMEA protocol. Output from
              > the TNC to the radio is (I assume) AX.25 standard.
              >
              > Also, by restricted digipeat capability, I mean having the digipeater
              > listen only for packets from our chase vehicles, which would (I hope)
              > be the only packets on whatever frequency we chose. This frequency
              > should be different from the national APRS frequency.
              >
              > Thanks to everyone for their input.
              >
              > Jeremy Day
              > Communications Lead
              > Auburn High Altitude Balloon Team
              > space.auburn.edu
              >
            • Bob Burns W9RXR
              ... In the words of Jeff Foxworthy, you have my attention. Tell us more. How frequency agile will these RF boards be? How much current will they draw? What s
              Message 6 of 9 , Sep 7 1:20 AM
                At 04:25 PM 9/6/2007, Scott Miller wrote:
                >If and when I get a compact transceiver an all-in-one T2 would be a
                >possibility. In fact, I'm doing that with the more expensive
                >commercial 6-watt RF boards.

                In the words of Jeff Foxworthy, you have my attention.

                Tell us more. How frequency agile will these RF boards be? How much
                current will they draw? What's your time line for this project?

                Bob...
              • Scott Miller
                Catching up on email again... The commercial boards will do 136 to 162 MHz in 2.5 kHz steps. Transmitter attack time is under 15 ms. Current drain at 6 watts
                Message 7 of 9 , Sep 18 6:04 PM
                  Catching up on email again...

                  The commercial boards will do 136 to 162 MHz in 2.5 kHz steps.
                  Transmitter attack time is under 15 ms. Current drain at 6 watts is a
                  little over 2 amps. Receive current is about 80 mA.

                  They're really not meant for high duty cycles - the PA starts heating up
                  really fast. For testing, I've bolted a couple of the largest TO-220
                  heatsinks I had on hand to the thing and it does much better - I don't
                  have to worry about a software glitch locking it in transmit mode for 20
                  seconds and cooking the board.

                  Scott

                  Bob Burns W9RXR wrote:
                  >
                  >
                  > At 04:25 PM 9/6/2007, Scott Miller wrote:
                  > >If and when I get a compact transceiver an all-in-one T2 would be a
                  > >possibility. In fact, I'm doing that with the more expensive
                  > >commercial 6-watt RF boards.
                  >
                  > In the words of Jeff Foxworthy, you have my attention.
                  >
                  > Tell us more. How frequency agile will these RF boards be? How much
                  > current will they draw? What's your time line for this project?
                  >
                  > Bob...
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