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Re: Multiple Decodes - r3158 & r3166

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  • LA3ZA
    I think you are right, it must come from the receiver end, not the transmitter. I just documented an example of a US station received here in Europe with 100
    Message 1 of 14 , Apr 28, 2013
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      I think you are right, it must come from the receiver end, not the transmitter. 

      I just documented an example of a US station received here in Europe with 100 Hz and not 120 Hz sidebands, see my blog http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html

      And the US station happens to be K1JT.


      73

      Sverre

      LA3ZA


      --- In wsjtgroup@yahoogroups.com, Colin XSD wrote:
      >
      > I would imagine the ghost images are on the Rx end if you are
      > consistently seeing +/- 120Hz otherwise you would see +/- 100Hz from
      > European signals (due to the 50Hz mains frequency).
      >
      > 73, Colin M0XSD.
      >
      >
      >
    • qrpbear
      Sverre, If it was from the receiver end the multiple decodes would show up consistently on all transmissions with signals stronger than some particular level.
      Message 2 of 14 , Apr 28, 2013
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        Sverre,

        If it was from the receiver end the multiple decodes would show up consistently on all transmissions with signals stronger than some particular level.

        From my QTH in Honolulu I have seen multiples at both 100 and 120Hz differentials. I have seen signals decode with close to the same SNR but with the weaker showing the multiples which were lacking on the stronger. I'm inclined to believe that the problem is more related to the transmitter end and primarily due to presence of ground loops and/or rf getting into the audio interface. The isolation transformers that many rig interfaces use do a good job of breaking the galvanic path but... quite often they are quite hum sensors!

        73,

        'Bear' NH7SR

        --- In wsjtgroup@yahoogroups.com, "LA3ZA" <svholm54@...> wrote:
        >
        > I think you are right, it must come from the receiver end, not the
        > transmitter. 
        >
        > I just documented an example of a US station received here in Europe
        > with 100 Hz and not 120 Hz sidebands, see my blog
        > http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html
        > <http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html>
        >
        > And the US station happens to be K1JT.
        >
        >
        >
        > 73
        >
        > Sverre
        >
        > LA3ZA
        >
        >
        >
        > --- In wsjtgroup@yahoogroups.com, Colin XSD wrote:
        > >
        > > I would imagine the ghost images are on the Rx end if you are
        > > consistently seeing +/- 120Hz otherwise you would see +/- 100Hz from
        > > European signals (due to the 50Hz mains frequency).
        > >
        > > 73, Colin M0XSD.
        >
      • Mirel Cardoso
        Amateur is french for LOVER . (Radiolover) Soixante treize Mirel VK2BOD ... From: LA3ZA Date: 28/04/13 23:34:05 To: Colin XSD; wsjtgroup@yahoogroups.com
        Message 3 of 14 , Apr 28, 2013
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          Amateur is french for LOVER .    (Radiolover)
           
          Soixante treize
           
          Mirel
           
          VK2BOD 
           
           
           
           
          -------Original Message-------
           
          From: LA3ZA
          Date: 28/04/13 23:34:05
          Subject: [wsjtgroup] Re: Multiple Decodes - r3158 & r3166
           
           

          I think you are right, it must come from the receiver end, not the transmitter. 

          I just documented an example of a US station received here in Europe with 100 Hz and not 120 Hz sidebands, see my blog http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html

          And the US station happens to be K1JT.



          73

          Sverre

          LA3ZA


          --- In wsjtgroup@yahoogroups.com, Colin XSD wrote:
          >
          > I would imagine the ghost images are on the Rx end if you are
          > consistently seeing +/- 120Hz otherwise you would see +/- 100Hz from
          > European signals (due to the 50Hz mains frequency).
          >
          > 73, Colin M0XSD.

           
        • Colin XSD
          Good to know my theory (aka guess) was right. Out of interest, I have been getting Multiple Decodes on WSPR 2.11 as well (I have been doing some WSPR Rx tests
          Message 4 of 14 , Apr 29, 2013
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            Good to know my theory (aka guess) was right.

            Out of interest, I have been getting Multiple Decodes on WSPR 2.11 as well (I have been doing some WSPR Rx tests ready for when my Hans Summers Ultimate2 QRSS Kit arrives).

            I have noticed 50Hz duplicates with WSPR 2.11 and also WSJT-X but 100Hz seems the stronger with WSJT. There are even some 150hz dupicates.

            It would appear that anything in the negative single digit dB and stronger will produce Duplicates here with the duplicates about 20dB down on the strongest signal.

            I am yet to receive anything strong enough from aross the pond to confirm or deny my theory myself.

            Please see attached screen shot of my WSPR 2.11 for an example.

            I was wondering if some form of duplicate suppression could be incorporated into future incarnations of WSJT & WSPR?. Perhaps only on the reporting side of things and some sort of Highlighting of the strongest signal on the display (or Lowlighting of the weaker ones, smaller font, pale color perhaps)?.

            It is all good fun anyway :-)
            73,
            Colin
            M0XSD.

            On 28/04/2013 13:19, LA3ZA wrote:
            I think you are right, it must come from the receiver end, not the transmitter. 

            I just documented an example of a US station received here in Europe with 100 Hz and not 120 Hz sidebands, see my blog http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html

            And the US station happens to be K1JT.



            73

            Sverre

            LA3ZA


            --- In wsjtgroup@yahoogroups.com, Colin XSD wrote:
            >
            > I would imagine the ghost images are on the Rx end if you are
            > consistently seeing +/- 120Hz otherwise you would see +/- 100Hz from
            > European signals (due to the 50Hz mains frequency).
            >
            > 73, Colin M0XSD.


          • qrpbear
            Colin, Here s an easy test to check if the +/- ghosts are in your rx setup or the other guy s tx... Go to 30 mtrs and set your rx dial frequency to 10138.5
            Message 5 of 14 , Apr 29, 2013
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              Colin,

              Here's an easy test to check if the +/- "ghosts" are in your rx setup or the other guy's tx...

              Go to 30 mtrs and set your rx dial frequency to 10138.5 instead of 10138.7. This should bring QRSS signals onto your WSPR 2.11 waterfall. Most QRSS rigs have well filtered power supplies and are rarely connected to a computer. If you consistently see the ghost frequencies on the stronger QRSS signals then the problem is related to ground looping, insufficient filtering or insufficient isolation on your end. You can repeat the test by tuning to 40 mtrs CW and watching for the same pattern there. It's not as conclusive as the QRSS test since these days most of us seem to have our rigs hooked up to a computer. Despite that it may give you a better idea of where the ghost signals are originating.

              73,

              'Bear' NH7SR
            • Colin XSD
              Thanks Bear, I will give that test a try sometime but I don t hold out much hope of picking up any strong QRSS signals (I haven t in the past when I ve tried).
              Message 6 of 14 , Apr 29, 2013
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                Thanks Bear,

                I will give that test a try sometime but I don't hold out much hope of picking up any strong QRSS signals (I haven't in the past when I've tried). I'm busy using the Rig for APRS at the moment, so it will have to wait until later (or more likely tomorrow).

                But I do highly suspect ground loops since I run an IC-706 MkII with a long seperation kit and a long cable to the computer.

                I am looking to improve the setup here but to be honest I'm surprised it works as well as it does.

                I am waiting for a Hans Summers Ultimate2 QRSS Kit to arrive, so when that is built I can use that for some tests. I'm planning on using it on 40m and/or 10m (depending on band conditions) for WSPR but do you (or anyone else here) know what the QRSS frequencies for those bands are?


                73,
                Colin
                M0XSD.

                On 29/04/2013 07:56, qrpbear wrote:
                 

                Colin,

                Here's an easy test to check if the +/- "ghosts" are in your rx setup or the other guy's tx...

                Go to 30 mtrs and set your rx dial frequency to 10138.5 instead of 10138.7. This should bring QRSS signals onto your WSPR 2.11 waterfall. Most QRSS rigs have well filtered power supplies and are rarely connected to a computer. If you consistently see the ghost frequencies on the stronger QRSS signals then the problem is related to ground looping, insufficient filtering or insufficient isolation on your end. You can repeat the test by tuning to 40 mtrs CW and watching for the same pattern there. It's not as conclusive as the QRSS test since these days most of us seem to have our rigs hooked up to a computer. Despite that it may give you a better idea of where the ghost signals are originating.

                73,

                'Bear' NH7SR


              • Joe Subich, W4TV
                ... Most probably due to ground loop in the *receive* audio chain. 100 Hz is the expected ripple frequency for a full wave rectified, linear supply power
                Message 7 of 14 , Apr 30, 2013
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                  > I just documented an example of a US station received here in Europe
                  > with 100 Hz and not 120 Hz sidebands, see my blog

                  Most probably due to "ground loop" in the *receive* audio chain.
                  100 Hz is the expected ripple frequency for a full wave rectified,
                  linear supply power supply. Note: "ripple modulation" can occur
                  on either the transmit *or* receive end of the communications
                  channel. In this case, it appears to be happening on receive.

                  The simple explanation is that the ripple current passes on the shield
                  of the audio line between transceiver and sound card. That current
                  "modulates" the ground reference of the sound card which causes
                  responses at F(undamental) +/- the "modulation" frequency. If the
                  fundamental is strong enough, the modulation sidebands will rise
                  above the ADC threshold (or above the "sky noise") and be detected
                  by the software. The relative level of the "ghosts" is an indication
                  of the relative level of the "hum" in a given station configuration.

                  73,

                  ... Joe, W4TV


                  On 4/28/2013 9:24 AM, LA3ZA wrote:
                  > I think you are right, it must come from the receiver end, not the
                  > transmitter.
                  >
                  > I just documented an example of a US station received here in Europe
                  > with 100 Hz and not 120 Hz sidebands, see my blog
                  > http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html
                  > <http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html>
                  >
                  >
                  > And the US station happens to be K1JT.
                  >
                  >
                  >
                  > 73
                  >
                  > Sverre
                  >
                  > LA3ZA
                  >
                  > --- In wsjtgroup@yahoogroups.com, Colin XSD wrote:
                  >>
                  >> I would imagine the ghost images are on the Rx end if you are
                  >> consistently seeing +/- 120Hz otherwise you would see +/- 100Hz from
                  >> European signals (due to the 50Hz mains frequency).
                  >>
                  >> 73, Colin M0XSD.
                  >>
                  >>
                  >>
                  >
                  >
                • Sverre Holm
                  Ground loops etc could be a good explanation if it weren t for the experience I have that the multiples seldom are there. They only come from time to time,
                  Message 8 of 14 , Apr 30, 2013
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                    Ground loops etc could be a good explanation if it weren't for the experience I have that the multiples seldom are there. They only come from time to time, without me rewiring or changing the K3-PC connection in anyway. So it is a little mysterious, but it could of course depend on some other variable here in my shack that I cannot see now.

                    73,
                    Sverre
                    LA3ZA


                    2013/4/30 Joe Subich, W4TV <lists@...>

                    > I just documented an example of a US station received here in Europe
                    > with 100 Hz and not 120 Hz sidebands, see my blog

                    Most probably due to "ground loop" in the *receive* audio chain.
                    100 Hz is the expected ripple frequency for a full wave rectified,
                    linear supply power supply.  Note: "ripple modulation" can occur
                    on either the transmit *or* receive end of the communications
                    channel.  In this case, it appears to be happening on receive.

                    The simple explanation is that the ripple current passes on the shield
                    of the audio line between transceiver and sound card.  That current
                    "modulates" the ground reference of the sound card which causes
                    responses at F(undamental) +/- the "modulation" frequency.  If the
                    fundamental is strong enough, the modulation sidebands will rise
                    above the ADC threshold (or above the "sky noise") and be detected
                    by the software.  The relative level of the "ghosts" is an indication
                    of the relative level of the "hum" in a given station configuration.

                    73,

                       ... Joe, W4TV



                    On 4/28/2013 9:24 AM, LA3ZA wrote:
                    I think you are right, it must come from the receiver end, not the
                    transmitter.

                    I just documented an example of a US station received here in Europe
                    with 100 Hz and not 120 Hz sidebands, see my blog
                    http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html
                    <http://la3za.blogspot.no/2013/04/jt9-and-100-hz-ghosts.html>


                    And the US station happens to be K1JT.



                    73

                    Sverre

                    LA3ZA

                    --- In wsjtgroup@yahoogroups.com, Colin XSD  wrote:

                    I would imagine the ghost images are on the Rx end if you are
                    consistently seeing +/- 120Hz otherwise you would see +/- 100Hz from
                    European signals (due to the 50Hz mains frequency).

                    73, Colin M0XSD.






                  • k3wyc
                    ... This message initially sent, by accident of the default, to Sverre but copied here for the group. In this case r3251 was in use: Today I saw a US station
                    Message 9 of 14 , May 11, 2013
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                      --- In wsjtgroup@yahoogroups.com, "LA3ZA" <svholm54@...> wrote:
                      >
                      > I think you are right, it must come from the receiver end, not the
                      > transmitter.
                      >

                      This message initially sent, by accident of the default, to Sverre but copied here for the group. In this case r3251 was in use:

                      Today I saw a US station on 15m JT9 with a primary and 4 image decodes. The spacing of the decodes was 100Hz (with both the RX and TX station in US).

                      1405 +4
                      1203 -21
                      1304 -12
                      1505 -10
                      1707 -23

                      The image at 160x was not decoded but was visible on the waterfall.

                      No other stations showed multiple decodes or visible images. Also no other station received this strong at other times produces images at my station. I have little doubt the issue was with the transmitting station.

                      I have screen snapshots and will share by private email. Don't wish to publish here without approval of the transmitting station.

                      Andy k3wyc
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