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Spurious Output on WSJT Setup

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  • aj6t@comcast.net
    Fellow WSJTers, I need some help with a problem I have run into with a new WSJT station I am attempting to run from a portable setup in a hotel room. I
    Message 1 of 5 , May 4, 2004
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      Fellow WSJTers,

      I need some help with a problem I have run into with a new WSJT station I am attempting to run from a portable setup in a hotel room. I brought an FT-100, dipole antenna, lightweight switching PS, EZ-PSK cable (with special Heil mike connector dongle) and Sony Vaio laptop (model PCG-XG29)along on a business trip to Waco, Texas, in the hope of making a few assisted FSK441 QSOs in the MS Rally from here as AJ6T/5. Receiving works fine and I decoded some strong pings this morning from N5SIX and WA5UFH. However, attempting to key the rig via the usual RS232 PPT control results in an immediate RF output, even with the TX audio from the computer turned all the way down (or muted in the Windows sound control panel). It appears to me to be feedback or spurious hash pickup into the FT-100 mike input. The unexpected RF output stops if the computer audio output line (which goes to the rig mike input) is disconnected. Of course, I have no tools or other diagnostic equipment with me on the road.

      Any suggestions for ways to get this lashup operational would be appreciated.

      73,

      Walt, AJ6T/5
      EM11ko
    • bbrackin@bellsouth.net
      Walt - I sure you have great ground! Had similar but not as bad a problem on mobile setup. For a temp fix coil the lines to and from interface - may act as
      Message 2 of 5 , May 4, 2004
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        Fellow WSJTers,

        I need some help with a problem I have run into with a new WSJT station I am attempting to run from a portable setup in a hotel room.  I brought an FT-100, dipole antenna, lightweight switching PS, EZ-PSK cable (with special Heil mike connector dongle) and Sony Vaio laptop (model PCG-XG29)along on a business trip to Waco, Texas, in the hope of making a few assisted FSK441 QSOs in the MS Rally from here as AJ6T/5.  Receiving works fine and I decoded some strong pings this morning from N5SIX and WA5UFH.  However, attempting to key the rig via the usual RS232 PPT control results in an immediate RF output, even with the TX audio from the computer turned all the way down (or muted in the Windows sound control panel).  It appears to me to be feedback or spurious hash pickup into the FT-100 mike input.  The unexpected RF output stops if the computer audio output line (which goes to the rig mike input) is disconnected.  Of course, I have no tools or other diagnostic equipment with me on the road.

        Any suggestions for ways to get this lashup operational would be appreciated.

        73,

        Walt, AJ6T/5
        EM11ko


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      • Russ Pillsbury
        Well you didn t tell us how the computer is connected to the FT100. Is is a direct connect, or via an interface such as a Rig Blaster? Are all the
        Message 3 of 5 , May 4, 2004
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          Well you didn't tell us how the computer is connected to the FT100. Is is a
          direct connect, or via an interface such as a Rig Blaster? Are all the
          connections shielded? Can you connect headphones or a speaker to the output
          of the computer in order to assure yourself that the computer is not putting
          out any audio when it should not be?

          Laptop computers usually have a built in microphone. Make sure that
          microphone is not enabled or you may be amplifying room noises and
          transmitting them. Make sure all equipment, especially the computer is well
          grounded to the radio (via the signal connector shields, and via the power
          supply grounds or extra ground wiring if possible/necessary).

          Once you have verified all the above, how about the SWR of the antenna and
          the proximity of the antenna to the rig. Check all your RF connectors
          carefully for loose or broken grounds. Make sure the antenna is not placed
          where it can be severely detuned by nearby metal objects (check the SWR, I
          think the FT100 has built in SWR detector). Position the radio as far from
          the antenna as possible, and away from the direction where the antenna is
          pointed (even a dipole is directional). Reduce the drive (output level) of
          the transmitter so you are only running about 10 watts (or turn off the
          amplifier if you are using one) and see if that reduces or eliminates the
          problem.

          The above should tell you if it is an RF feedback problem. If so, take a
          run to the nearest Radio Shack. Buy some ferrite beads and chokes, and some
          small disc ceramic capacitors (200 - 5000 pf., value not critical but 1000
          pf nominal), and a small soldering pencil and some solder, small wire
          cutters and needle-nose pliers. Unsolder the audio input wire (from the
          computer) from the mic connector and insert the ferrite bead and solder it
          back on. Do the same for the PTT wire. Then solder some of the disc
          ceramic capacitors from both of those leads to the ground connection going
          into the radio. Use the shortest leads possible. (Once you have done this,
          you may have to leave the cover off of the connector because it won't fit
          with the extra components in there).

          Also, wonder if you tried your setup before you left home, and if it
          transmitted ok then?

          Hope some of this helps,

          73, Russ K2TXB

          > -----Original Message-----
          > From: aj6t@... [mailto:aj6t@...]
          > Sent: Tuesday, May 04, 2004 12:11 PM
          > To: wsjtgroup@yahoogroups.com
          > Subject: [wsjtgroup] Spurious Output on WSJT Setup
          >
          >
          > Fellow WSJTers,
          >
          > I need some help with a problem I have run into with a new WSJT
          > station I am attempting to run from a portable setup in a hotel
          > room. I brought an FT-100, dipole antenna, lightweight switching
          > PS, EZ-PSK cable (with special Heil mike connector dongle) and
          > Sony Vaio laptop (model PCG-XG29)along on a business trip to
          > Waco, Texas, in the hope of making a few assisted FSK441 QSOs in
          > the MS Rally from here as AJ6T/5. Receiving works fine and I
          > decoded some strong pings this morning from N5SIX and WA5UFH.
          > However, attempting to key the rig via the usual RS232 PPT
          > control results in an immediate RF output, even with the TX audio
          > from the computer turned all the way down (or muted in the
          > Windows sound control panel). It appears to me to be feedback or
          > spurious hash pickup into the FT-100 mike input. The unexpected
          > RF output stops if the computer audio output line (which goes to
          > the rig mike input) is disconnected. Of course, I have no tools
          > or other diagnostic equipment with me on the road.
          >
          > Any suggestions for ways to get this lashup operational would be
          > appreciated.
          >
          > 73,
          >
          > Walt, AJ6T/5
          > EM11ko
        • aj6t@comcast.net
          Bruce and Russ, Thanks for your replies. After a bit more investigation, I think the fundamental problem is related to the infamous FT-100 Hi-SWR situation
          Message 4 of 5 , May 5, 2004
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            Bruce and Russ,

            Thanks for your replies.

            After a bit more investigation, I think the fundamental problem is related to the infamous FT-100 "Hi-SWR" situation that has been well documented on various FT-100 websites. The Yaesu fix for this unfortunate problem with the FT-100 involves the addition of extra internal shielding and grounding inside the radio. That particular "fix" has only been partially implemented on my old radio. When I get home from this trip I will dig into the rig and replace some of the flimsy conductive tape straps that were added by Yaesu to attempt to cure the rig's tendency to oscillate/shutdown accompanied by a false "Hi-SWR" indication even when the antenna match is OK.

            The SWR on my hotel room dipole is OK at about 1.7 as indicated by an MFJ Antenna Analyzer. The SWR does dip nicely at resonance at the low end of the 6m band.

            In any event, I did go to Radio Shack yesterday and I purchased four Snap-on Ferrite Date Line Filters (P/N 273-105). I installed them at both ends of the audio cables running from the computer to the rig. As mentioned in my original message, I am using a simple interface called "EZ-PSK" made by Saratoga Radio Products which is much smaller and lighter than a Rigblaster. This interface has audio isolation transformers and optoisolation for RS232 PTT keying. Addition of the ferrite chokes seemed to make the setup even more prone to spurious output. I also tried various additional ground jumpers between rig/computer/PS/ACgnd and a counterpoise wire without any real improvement.

            I'll stick to SSB operation on this short trip. Thanks for your help. I'll be back in CM87 on Friday.

            73,

            Walt, AJ6T/5
            EM11ko
            > Walt - I sure you have great ground! Had similar but not as bad a problem on
            > mobile setup. For a temp fix coil the lines to and from interface - may act as
            > rf choke to so limited extent. My final fix was rewiring interface with shorter
            > and more heavily sheilded cables and a few snap-on beads. Also I have found I
            > have less rf problems if I crank audio up from pc and use lower setting on AFSK
            > setting on the FT-100. I think the AFSK is at about 18-20 range with 50MHz Po
            > at about 20 also to give 8-10 watts to brick. My guess is the high level is a
            > little less likely to have rf induced on it - at least in proportional sense.
            >
            > Glad you heard me! GL - Bruce N5SIX
            >
            >
            >
            and K2TXB wrote:

            Well you didn't tell us how the computer is connected to the FT100. Is is a
            direct connect, or via an interface such as a Rig Blaster? Are all the
            connections shielded? Can you connect headphones or a speaker to the output
            of the computer in order to assure yourself that the computer is not putting
            out any audio when it should not be? <snip>
          • Russ Pillsbury
            Sorry Walt, I did not recognize EZ-PSK as an interface. Sorry you were not able to fix the problem. You didn t comment on the antenna spacing (from the rig)
            Message 5 of 5 , May 5, 2004
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              Sorry Walt, I did not recognize EZ-PSK as an interface. Sorry you were not
              able to fix the problem. You didn't comment on the antenna spacing (from
              the rig) issue, but I'd still try to get further from the antenna -
              especially if the antenna is in the room. If you can get it outside the
              room, and separated from the room by the window screen (if there is one)
              that might help a lot.

              Good luck, Russ K2TXB

              > -----Original Message-----
              > From: aj6t@... [mailto:aj6t@...]
              > Sent: Wednesday, May 05, 2004 7:19 AM
              > To: wsjtgroup@yahoogroups.com
              > Subject: Re: [wsjtgroup] Spurious Output on WSJT Setup
              >
              >
              > Bruce and Russ,
              >
              > Thanks for your replies.
              >
              > After a bit more investigation, I think the fundamental problem
              > is related to the infamous FT-100 "Hi-SWR" situation that has
              > been well documented on various FT-100 websites. The Yaesu fix
              > for this unfortunate problem with the FT-100 involves the
              > addition of extra internal shielding and grounding inside the
              > radio. That particular "fix" has only been partially implemented
              > on my old radio. When I get home from this trip I will dig into
              > the rig and replace some of the flimsy conductive tape straps
              > that were added by Yaesu to attempt to cure the rig's tendency to
              > oscillate/shutdown accompanied by a false "Hi-SWR" indication
              > even when the antenna match is OK.
              >
              > The SWR on my hotel room dipole is OK at about 1.7 as indicated
              > by an MFJ Antenna Analyzer. The SWR does dip nicely at resonance
              > at the low end of the 6m band.
              >
              > In any event, I did go to Radio Shack yesterday and I purchased
              > four Snap-on Ferrite Date Line Filters (P/N 273-105). I
              > installed them at both ends of the audio cables running from the
              > computer to the rig. As mentioned in my original message, I am
              > using a simple interface called "EZ-PSK" made by Saratoga Radio
              > Products which is much smaller and lighter than a Rigblaster.
              > This interface has audio isolation transformers and optoisolation
              > for RS232 PTT keying. Addition of the ferrite chokes seemed to
              > make the setup even more prone to spurious output. I also tried
              > various additional ground jumpers between rig/computer/PS/ACgnd
              > and a counterpoise wire without any real improvement.
              >
              > I'll stick to SSB operation on this short trip. Thanks for your
              > help. I'll be back in CM87 on Friday.
              >
              > 73,
              >
              > Walt, AJ6T/5
              > EM11ko
              > > Walt - I sure you have great ground! Had similar but not as
              > bad a problem on
              > > mobile setup. For a temp fix coil the lines to and from
              > interface - may act as
              > > rf choke to so limited extent. My final fix was rewiring
              > interface with shorter
              > > and more heavily sheilded cables and a few snap-on beads. Also
              > I have found I
              > > have less rf problems if I crank audio up from pc and use lower
              > setting on AFSK
              > > setting on the FT-100. I think the AFSK is at about 18-20
              > range with 50MHz Po
              > > at about 20 also to give 8-10 watts to brick. My guess is the
              > high level is a
              > > little less likely to have rf induced on it - at least in
              > proportional sense.
              > >
              > > Glad you heard me! GL - Bruce N5SIX
              > >
              > >
              > >
              > and K2TXB wrote:
              >
              > Well you didn't tell us how the computer is connected to the
              > FT100. Is is a
              > direct connect, or via an interface such as a Rig Blaster? Are all the
              > connections shielded? Can you connect headphones or a speaker to
              > the output
              > of the computer in order to assure yourself that the computer is
              > not putting
              > out any audio when it should not be? <snip>
              >
              >
              >
              > To unsubscribe, send an email to:
              > wsjtgroup-unsubscribe@yahoogroups.com
              > Activity Periods http://www.qsl.net/wa5ufh/WSJTGROUP/WSJTGROUP.htm
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