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Re: RF and the TNC-X

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  • 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 1 of 7 , Apr 2, 2008
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      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 2 of 7 , Apr 2, 2008
      • 0 Attachment
        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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