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WSJT-X For Backpacking To Rare Grid

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  • Jim Brown
    I was chatting yesterday with AF6RT, a member with me of NCCC and NCDXC who lives in San Francisco. Scott has no station in his nice San Francisco townhouse,
    Message 1 of 9 , Jul 21, 2014
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      I was chatting yesterday with AF6RT, a member with me of NCCC and NCDXC
      who lives in San Francisco. Scott has no station in his nice San
      Francisco townhouse, but has so far made two hiking expeditions to
      activate CM79 on 6M, a grid that is 99.9% water. His most recent trip
      was for the CQ VHF contest this past weekend. This is a challenging
      hike, so he needs to get maximum bang for every pound of gear. As it is,
      he's making two trips each way to haul stuff. He doesn't know CW, and
      has been working only SSB. That burns lots of battery, and he ran it
      down calling CQ.

      My contribution was to help him think about system engineering, with a
      multi-prong approach to maximize efficiency and minimize weight. I've
      urged him to use JT9, with a strategy that those who want to work him
      calling at the right time and frequency, and he TXs only when he copies
      a call. Also, he uses the indicated SNR to gauge how much TX power to
      use. He's been using a K3, and I've suggested the KX3 to minimize RX
      current (200 mA as compared to 1A) with the KXPA100 amp.

      I've suggested that he replace the lead-acid batteries he's been using
      with Li-Ion polymer or phosphate to save weight. It's that power amp
      that really burns the joules.

      Now, the question for this group -- what are the most power-efficient,
      weight-efficient hardware and OS platforms for running WSJT-X? He will
      need a high quality audio interface -- I'll suggest the Numark, which
      gets power from it's USB connection. Scott is a software engineer,
      writing lots of code, so compiling for another platform is no big deal.

      There's plenty of lead-time to work this out -- thanks to work
      committments, his next window of opportunity is Memorial Day, 2015.

      73, Jim K9YC
    • Jim Brown
      ... Thanks, Rick. Can you define good? What s the running time on a battery charge? Replaceable battery? Charging voltage? The specs say it uses a 36W
      Message 2 of 9 , Jul 21, 2014
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        On 7/21/2014 4:27 PM, Rick N8SDR wrote:
        > Does good on power consumption

        Thanks, Rick.

        Can you define "good?" What's the running time on a battery charge?
        Replaceable battery? Charging voltage? The "specs" say it uses a 36W
        power supply, but does not specify voltage.

        73, Jim K9YC
      • k3wyc
        JT9 on 6m requires a VFO with good stability. I m new to 6m but I see far more JT65 than JT9 signals when the band is open. The few JT9 signals that I do
        Message 3 of 9 , Jul 22, 2014
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          JT9 on 6m requires a VFO with good stability.     I'm new to 6m but I see far more JT65 than JT9 signals when the band is open.  The few JT9 signals that I do see often have frequency drift and most don't decode.  JT65 signals with obvious frequency drift decode most of the time.


          JT65 may be a better option.


          73,

          Andy k3wyc

        • Joe Taylor
          JT65 is *definitely* a better option for 6m. It s hardly accidental that the docs explain that JT9 was designed for use at LF, MF, and HF. Using JT9 even on
          Message 4 of 9 , Jul 22, 2014
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            JT65 is *definitely* a better option for 6m. It's hardly accidental
            that the docs explain that JT9 was designed for use at LF, MF, and HF.
            Using JT9 even on 10 m is a stretch, for some of today's radios.

            -- Joe, K1JT

            On 7/22/2014 10:35 AM, a.durbin@... [wsjtgroup] wrote:
            > JT9 on 6m requires a VFO with good stability. I'm new to 6m but I see far more JT65 than JT9 signals when the band is open. The few JT9 signals that I do see often have frequency drift and most don't decode. JT65 signals with obvious frequency drift decode most of the time.
            >
            >
            > JT65 may be a better option.
            >
            >
            > 73,
            > Andy k3wyc
            >
          • g4wjs
            I ll second that, and it s not just the radio capabilities that cause issues with JT9 on 6m. I often see strong reflections with a fast Doppler shift just
            Message 5 of 9 , Jul 22, 2014
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              I'll second that, and it's not just the radio capabilities that cause issues with JT9 on 6m. I often see strong reflections with a fast Doppler shift just below JT9 signals on 6m and that component seems to degrade decoding severely. I assume these are aircraft reflections.

              73
              Bill
              G4WJS.
            • Sean Gardner
              I m not familiar with JT9 so I have no comments there, but as for power consumtion I will offer what I know. first off I do a fare amount of SOTA and therefore
              Message 6 of 9 , Jul 22, 2014
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                I'm not familiar with JT9 so I have no comments there, but as for power consumtion I will offer what I know.


                first off I do a fare amount of SOTA and therefore have experience backpacking all the gear to the top of a peak and weight is a big factor at times depending on the dificulty of the peak that needs climbing. Also as said in another post, biggest bang for the buck power wise. We SOTA guys mostly go QRP for obviouse reasons. LiPo batteries are the way to go, they can be a little dangerous to charge at times but they will give you the power you want at a light weight. I use an FT-817 but I have friends who use KX3's and they have used these batteries too. you need to get the battery and a smart charger. I can charge up 2 of these batteries and spend ALL day calling cq on SSB and still have a little battery left over when I start back down the hill. just a thought, and if you are interested I can get my batteries when I get home and send more information on them, IE: model # of battery and charger.
                now I say these are the way to go, but just an FYI, they are external battery pack that will work on the radios with a small pigtail you may have to make. As for the the internal battery I use on my 817 also, that battery pack is a 2700 Ma NiMH, and it also will give me several hours of CQ calling on SSB (I'm not confident with my CW yet)


                I do have a question as to what antenna you are looking to use for the trip?

                73'
                Sean Gardner KD6CUB
                kd6cub@...


                --------------------------------------------
                On Tue, 7/22/14, bill.8@... [wsjtgroup] <wsjtgroup@yahoogroups.com> wrote:


                Subject: Re: [wsjtgroup] Re: WSJT-X For Backpacking To Rare Grid
                To: wsjtgroup@yahoogroups.com
                Date: Tuesday, July 22, 2014, 9:22 AM


                 









                I'll second that, and it's not just the
                radio capabilities that cause issues with JT9 on 6m. I often
                see strong reflections with a fast Doppler shift just below
                JT9 signals on 6m and that component seems to degrade
                decoding severely. I assume these are aircraft
                reflections.

                73
                Bill
                G4WJS.









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              • Jim Brown
                ... Thanks, Joe. I did study the doc file, and all I could find was JT65 signals often decode correctly even when they overlap. Such behavior is much less
                Message 7 of 9 , Jul 22, 2014
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                  On 7/22/2014 8:17 AM, Joe Taylor joe@... [wsjtgroup] wrote:
                  > JT65 is*definitely* a better option for 6m. It's hardly accidental
                  > that the docs explain that JT9 was designed for use at LF, MF, and HF.
                  > Using JT9 even on 10 m is a stretch, for some of today's radios.

                  Thanks, Joe.

                  I did study the doc file, and all I could find was "JT65 signals often
                  decode correctly even when they overlap. Such behavior is much less
                  likely with JT9 signals, which fill their occupied bandwisth more
                  densely. JT65 may also be more forgiving of small frequency drifts." Is
                  frequency stability the only hazard, or is there more? On 6M, I've
                  observed that I get decodes of JT9 signals when I've tuned to the
                  frequency a bit late in the cycle, or when the other station started TX
                  a bit late.

                  Back to systems engineering here. The purpose of this particular trip is
                  to supply the grid for serious 6M players chasing the Fred Fish award,
                  and for high-number grid chasers. These are not casual operators. Many
                  use a K3 or something like it, external power amp, serious antennas. I'm
                  using a K3, and stability is good enough for me, running it at 29W to
                  drive an external 500W amp. I don't see a lot of JT9 signals on 6M, but
                  nearly all of those I see I can decode, and I've had at least one decode
                  at -24.

                  I know that W7GJ had issues with KX3 stability on moonbounce, but I
                  think N6KR (designer) did some things to improve it. I don't know if
                  Lance's needs were satisfied. There is a high stability option for the
                  KX3, and I think Lance was starting with that. There are also
                  after-market heat sinks that mount to the chassis adjacent to the power
                  devices that would help.

                  73, Jim K9YC
                • Jim Brown
                  On 7/22/2014 10:34 AM, Jim Brown k9yc@audiosystemsgroup.com [wsjtgroup] ... Correction. There is NOT a high stability option for the KX3, but Wayne added a TC
                  Message 8 of 9 , Jul 22, 2014
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                    On 7/22/2014 10:34 AM, Jim Brown k9yc@... [wsjtgroup]
                    wrote:
                    > There is a high stability option for the
                    > KX3, and I think Lance was starting with that.

                    Correction. There is NOT a high stability option for the KX3, but Wayne
                    added a TC routine to the firmware to improve temperature stability.
                    It's a pretty straight-forward procedure, at least in concept, requiring
                    only a stable source around 50 MHz and a hair dryer or heat gun to heat
                    up the KX3.

                    73, Jim K9YC
                  • Joe Taylor
                    Hi Jim, ... Frequency stability, yes. Also, for EME use the JT65 decoder needs to allow for changing EME Doppler over the duration of a transmission. And any
                    Message 9 of 9 , Jul 23, 2014
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                      Hi Jim,

                      K9YC wrote:
                      > I did study the doc file, and all I could find was "JT65 signals often
                      > decode correctly even when they overlap. Such behavior is much less
                      > likely with JT9 signals, which fill their occupied bandwisth more
                      > densely. JT65 may also be more forgiving of small frequency drifts." Is
                      > frequency stability the only hazard, or is there more?

                      Frequency stability, yes. Also, for EME use the JT65 decoder needs to
                      allow for changing EME Doppler over the duration of a transmission. And
                      any propagation-induced Doppler spreading will be proportionally larger
                      at higher frequency.

                      > On 6M, I've
                      > observed that I get decodes of JT9 signals when I've tuned to the
                      > frequency a bit late in the cycle, or when the other station started TX
                      > a bit late.

                      This is normal, and applies to both JT65 and JT9. With signals somewhat
                      well above the normal threshold, good decodes can be obtained even when
                      significant portions of the transmission are absent.

                      -- Joe, K1JT
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