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RF and the TNC-X

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  • Tim N9PUZ
    I was doing some testing this afternoon with a plain TNC-X and the same TNC with the digipeater board installed. I had a hand held radio nearby on the bench
    Message 1 of 7 , Mar 16, 2008
      I was doing some testing this afternoon with a plain TNC-X and the
      same TNC with the digipeater board installed. I had a hand held radio
      nearby on the bench and noticed that if I forgot to switch to low
      power (1W) from high power (5W) the first time the TNC transmitted
      things would lock up and I had to power off the TNC and restart
      everything.

      Has anyone else experienced this problem? I wondered if putting the
      TX/RX, and PTT lines through some toroids before the wires got to the
      circuit board might alleviate the problem.

      In most cases the antenna would be farther away than a few feet. If
      you were operating an APRS station at a bike race or a VHF Winlink
      email station using hand held like I did in my testing a nearby
      antenna could be could be common. I'm not dis'ing the TNC-X but I
      tried an old KAM+ TNC and a KPC-3+ and neither of them exhibited the
      problem so I'm fairly certain it's something in the TNC-X.

      Tim, N9PUZ
    • Brian Wingfield
      Tim, I ve had a similar problem, only using an Alinco mobile rig. I have no problem transmitting on the 5 W setting, but tx on 50 W can cause the TNC-X s PTT
      Message 2 of 7 , Mar 17, 2008
        Tim,

        I've had a similar problem, only using an Alinco mobile rig. I have
        no problem transmitting on the 5 W setting, but tx on 50 W can cause
        the TNC-X's PTT line to lock in transmit. Since the modem chip in the
        TNC-X is always generating a tone, even when no data is being
        transmitted, this single tone is transmitted until I removed power
        from the TNC. This happened to me without any daughter boards
        installed.

        I put a snap on ferrite bead on the RS-232 line to the laptop, but I
        haven't tried any other remedies. I just use 5 W for now.

        Good subject, though. I hope to hear what others have done to remedy
        the situation.

        73,
        Brian, KO4FV

        On Sun, Mar 16, 2008 at 7:18 PM, Tim N9PUZ <tim.n9puz@...> wrote:
        >
        >
        >
        >
        >
        >
        > I was doing some testing this afternoon with a plain TNC-X and the
        > same TNC with the digipeater board installed. I had a hand held radio
        > nearby on the bench and noticed that if I forgot to switch to low
        > power (1W) from high power (5W) the first time the TNC transmitted
        > things would lock up and I had to power off the TNC and restart
        > everything.
        >
        > Has anyone else experienced this problem? I wondered if putting the
        > TX/RX, and PTT lines through some toroids before the wires got to the
        > circuit board might alleviate the problem.
        >
        > In most cases the antenna would be farther away than a few feet. If
        > you were operating an APRS station at a bike race or a VHF Winlink
        > email station using hand held like I did in my testing a nearby
        > antenna could be could be common. I'm not dis'ing the TNC-X but I
        > tried an old KAM+ TNC and a KPC-3+ and neither of them exhibited the
        > problem so I'm fairly certain it's something in the TNC-X.
        >
        > Tim, N9PUZ
        >
      • Jason Rausch
        I experienced this problem myself. The problem is caused by the keying transistor becomming saturated with RF and basically freezes in that state. I cured
        Message 3 of 7 , Mar 17, 2008
          I experienced this problem myself. The problem is caused by the
          keying transistor becomming saturated with RF and basically freezes
          in that state. I cured the problem with three 0.1uF caps. On the
          bottom side of the PCB, solder one from Base to Emitter, one from
          Emitter to Collector and One from Collector to Base. This cured my
          problems.

          Jason KE4NYV
          RPC Electronics
          www.rpc-electronics.com

          --- In tnc-x@yahoogroups.com, "Brian Wingfield" <wingfba@...> wrote:
          >
          > Tim,
          >
          > I've had a similar problem, only using an Alinco mobile rig. I have
          > no problem transmitting on the 5 W setting, but tx on 50 W can cause
          > the TNC-X's PTT line to lock in transmit. Since the modem chip in
          the
          > TNC-X is always generating a tone, even when no data is being
          > transmitted, this single tone is transmitted until I removed power
          > from the TNC. This happened to me without any daughter boards
          > installed.
          >
          > I put a snap on ferrite bead on the RS-232 line to the laptop, but I
          > haven't tried any other remedies. I just use 5 W for now.
          >
          > Good subject, though. I hope to hear what others have done to
          remedy
          > the situation.
          >
          > 73,
          > Brian, KO4FV
          >
          > On Sun, Mar 16, 2008 at 7:18 PM, Tim N9PUZ <tim.n9puz@...> wrote:
          > >
          > >
          > >
          > >
          > >
          > >
          > > I was doing some testing this afternoon with a plain TNC-X and the
          > > same TNC with the digipeater board installed. I had a hand held
          radio
          > > nearby on the bench and noticed that if I forgot to switch to low
          > > power (1W) from high power (5W) the first time the TNC
          transmitted
          > > things would lock up and I had to power off the TNC and restart
          > > everything.
          > >
          > > Has anyone else experienced this problem? I wondered if putting
          the
          > > TX/RX, and PTT lines through some toroids before the wires got
          to the
          > > circuit board might alleviate the problem.
          > >
          > > In most cases the antenna would be farther away than a few feet.
          If
          > > you were operating an APRS station at a bike race or a VHF
          Winlink
          > > email station using hand held like I did in my testing a nearby
          > > antenna could be could be common. I'm not dis'ing the TNC-X but I
          > > tried an old KAM+ TNC and a KPC-3+ and neither of them exhibited
          the
          > > problem so I'm fairly certain it's something in the TNC-X.
          > >
          > > Tim, N9PUZ
          > >
          >
        • Tim N9PUZ
          I was thinking of winding the audio and PTT leads through some toroids to get a lot of attenuation where things come in to the enclosure. An FT50-43 toroid
          Message 4 of 7 , Mar 17, 2008
            I was thinking of winding the audio and PTT leads through some toroids
            to get a lot of attenuation where things come in to the enclosure. An
            FT50-43 toroid (5MHz-500MHz RFI suppression) with just 5 or 6 turns
            should give around 10K Ohms at 144.390 MHz and let the audio and
            keying signal sail right on through. Perhaps

            This based on the calculator at <http://kitsandparts.com/toroids.php>.

            I've also found that it helps some if you scrape a little paint on the
            enclosure holes where the screws go so there's good metal-to-metal
            contact--helps provide a better shield but I suspect most of the
            problem is going right in on the cable.

            Tim, N9PUZ

            Brian Wingfield wrote:
            > Tim,
            >
            > I've had a similar problem, only using an Alinco mobile rig. I have
            > no problem transmitting on the 5 W setting, but tx on 50 W can cause
            > the TNC-X's PTT line to lock in transmit. Since the modem chip in the
            > TNC-X is always generating a tone, even when no data is being
            > transmitted, this single tone is transmitted until I removed power
            > from the TNC. This happened to me without any daughter boards
            > installed.
            >
            > I put a snap on ferrite bead on the RS-232 line to the laptop, but I
            > haven't tried any other remedies. I just use 5 W for now.
            >
            > Good subject, though. I hope to hear what others have done to remedy
            > the situation.
            >
            > 73,
            > Brian, KO4FV
            >
            > On Sun, Mar 16, 2008 at 7:18 PM, Tim N9PUZ <tim.n9puz@...> wrote:
            >>
            >> I was doing some testing this afternoon with a plain TNC-X and the
            >> same TNC with the digipeater board installed. I had a hand held radio
            >> nearby on the bench and noticed that if I forgot to switch to low
            >> power (1W) from high power (5W) the first time the TNC transmitted
            >> things would lock up and I had to power off the TNC and restart
            >> everything.
            >>
            >> Has anyone else experienced this problem? I wondered if putting the
            >> TX/RX, and PTT lines through some toroids before the wires got to the
            >> circuit board might alleviate the problem.
            >>
            >> In most cases the antenna would be farther away than a few feet. If
            >> you were operating an APRS station at a bike race or a VHF Winlink
            >> email station using hand held like I did in my testing a nearby
            >> antenna could be could be common. I'm not dis'ing the TNC-X but I
            >> tried an old KAM+ TNC and a KPC-3+ and neither of them exhibited the
            >> problem so I'm fairly certain it's something in the TNC-X.
            >>
            >> Tim, N9PUZ
          • Tim N9PUZ
            Jason, Thanks for the advice. Since I didn t have the toroid I was going to try but I had plenty of 0.1uF caps I added them and the problem seems cured. I can
            Message 5 of 7 , Mar 17, 2008
              Jason,

              Thanks for the advice. Since I didn't have the toroid I was going to
              try but I had plenty of 0.1uF caps I added them and the problem seems
              cured. I can now sit the TNC-X directly on top of the radio and even
              with an antenna about 5 ft away and running 25W it's all very happy.

              Tim, N9PUZ


              Jason Rausch wrote:
              > I experienced this problem myself. The problem is caused by the
              > keying transistor becomming saturated with RF and basically freezes
              > in that state. I cured the problem with three 0.1uF caps. On the
              > bottom side of the PCB, solder one from Base to Emitter, one from
              > Emitter to Collector and One from Collector to Base. This cured my
              > problems.
              >
              > Jason KE4NYV
              > RPC Electronics
              > www.rpc-electronics.com
            • cclcrac
              I too have had a similar problem and in my case a single 0.1 uF ceramic disc cap between emitter and collector worked fine. ... have ... cause ... in ... but I
              Message 6 of 7 , Apr 2, 2008
                I too have had a similar problem and in my case a single 0.1 uF
                ceramic disc cap between emitter and collector worked fine.


                --- In tnc-x@yahoogroups.com, "Jason Rausch" <lists@...> wrote:
                >
                > I experienced this problem myself. The problem is caused by the
                > keying transistor becomming saturated with RF and basically freezes
                > in that state. I cured the problem with three 0.1uF caps. On the
                > bottom side of the PCB, solder one from Base to Emitter, one from
                > Emitter to Collector and One from Collector to Base. This cured my
                > problems.
                >
                > Jason KE4NYV
                > RPC Electronics
                > www.rpc-electronics.com
                >
                > --- In tnc-x@yahoogroups.com, "Brian Wingfield" <wingfba@> wrote:
                > >
                > > Tim,
                > >
                > > I've had a similar problem, only using an Alinco mobile rig. I
                have
                > > no problem transmitting on the 5 W setting, but tx on 50 W can
                cause
                > > the TNC-X's PTT line to lock in transmit. Since the modem chip
                in
                > the
                > > TNC-X is always generating a tone, even when no data is being
                > > transmitted, this single tone is transmitted until I removed power
                > > from the TNC. This happened to me without any daughter boards
                > > installed.
                > >
                > > I put a snap on ferrite bead on the RS-232 line to the laptop,
                but I
                > > haven't tried any other remedies. I just use 5 W for now.
                > >
                > > Good subject, though. I hope to hear what others have done to
                > remedy
                > > the situation.
                > >
                > > 73,
                > > Brian, KO4FV
                > >
                > > On Sun, Mar 16, 2008 at 7:18 PM, Tim N9PUZ <tim.n9puz@> wrote:
                > > >
                > > >
                > > >
                > > >
                > > >
                > > >
                > > > I was doing some testing this afternoon with a plain TNC-X and
                the
                > > > same TNC with the digipeater board installed. I had a hand
                held
                > radio
                > > > nearby on the bench and noticed that if I forgot to switch to
                low
                > > > power (1W) from high power (5W) the first time the TNC
                > transmitted
                > > > things would lock up and I had to power off the TNC and restart
                > > > everything.
                > > >
                > > > Has anyone else experienced this problem? I wondered if
                putting
                > the
                > > > TX/RX, and PTT lines through some toroids before the wires got
                > to the
                > > > circuit board might alleviate the problem.
                > > >
                > > > In most cases the antenna would be farther away than a few
                feet.
                > If
                > > > you were operating an APRS station at a bike race or a VHF
                > Winlink
                > > > email station using hand held like I did in my testing a nearby
                > > > antenna could be could be common. I'm not dis'ing the TNC-X
                but I
                > > > tried an old KAM+ TNC and a KPC-3+ and neither of them
                exhibited
                > the
                > > > problem so I'm fairly certain it's something in the TNC-X.
                > > >
                > > > Tim, N9PUZ
                > > >
                > >
                >
              • cclcrac
                I too have had a similar problem and in my case a single 0.1 uF ceramic disc cap between emitter and collector worked fine. ... have ... cause ... in ... but I
                Message 7 of 7 , Apr 2, 2008
                  I too have had a similar problem and in my case a single 0.1 uF
                  ceramic disc cap between emitter and collector worked fine.


                  --- In tnc-x@yahoogroups.com, "Jason Rausch" <lists@...> wrote:
                  >
                  > I experienced this problem myself. The problem is caused by the
                  > keying transistor becomming saturated with RF and basically freezes
                  > in that state. I cured the problem with three 0.1uF caps. On the
                  > bottom side of the PCB, solder one from Base to Emitter, one from
                  > Emitter to Collector and One from Collector to Base. This cured my
                  > problems.
                  >
                  > Jason KE4NYV
                  > RPC Electronics
                  > www.rpc-electronics.com
                  >
                  > --- In tnc-x@yahoogroups.com, "Brian Wingfield" <wingfba@> wrote:
                  > >
                  > > Tim,
                  > >
                  > > I've had a similar problem, only using an Alinco mobile rig. I
                  have
                  > > no problem transmitting on the 5 W setting, but tx on 50 W can
                  cause
                  > > the TNC-X's PTT line to lock in transmit. Since the modem chip
                  in
                  > the
                  > > TNC-X is always generating a tone, even when no data is being
                  > > transmitted, this single tone is transmitted until I removed power
                  > > from the TNC. This happened to me without any daughter boards
                  > > installed.
                  > >
                  > > I put a snap on ferrite bead on the RS-232 line to the laptop,
                  but I
                  > > haven't tried any other remedies. I just use 5 W for now.
                  > >
                  > > Good subject, though. I hope to hear what others have done to
                  > remedy
                  > > the situation.
                  > >
                  > > 73,
                  > > Brian, KO4FV
                  > >
                  > > On Sun, Mar 16, 2008 at 7:18 PM, Tim N9PUZ <tim.n9puz@> wrote:
                  > > >
                  > > >
                  > > >
                  > > >
                  > > >
                  > > >
                  > > > I was doing some testing this afternoon with a plain TNC-X and
                  the
                  > > > same TNC with the digipeater board installed. I had a hand
                  held
                  > radio
                  > > > nearby on the bench and noticed that if I forgot to switch to
                  low
                  > > > power (1W) from high power (5W) the first time the TNC
                  > transmitted
                  > > > things would lock up and I had to power off the TNC and restart
                  > > > everything.
                  > > >
                  > > > Has anyone else experienced this problem? I wondered if
                  putting
                  > the
                  > > > TX/RX, and PTT lines through some toroids before the wires got
                  > to the
                  > > > circuit board might alleviate the problem.
                  > > >
                  > > > In most cases the antenna would be farther away than a few
                  feet.
                  > If
                  > > > you were operating an APRS station at a bike race or a VHF
                  > Winlink
                  > > > email station using hand held like I did in my testing a nearby
                  > > > antenna could be could be common. I'm not dis'ing the TNC-X
                  but I
                  > > > tried an old KAM+ TNC and a KPC-3+ and neither of them
                  exhibited
                  > the
                  > > > problem so I'm fairly certain it's something in the TNC-X.
                  > > >
                  > > > Tim, N9PUZ
                  > > >
                  > >
                  >
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