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PTT through FET not working on a rangr mobile radio

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  • Rob
    I can manually short the PTT to Ground and all is well but when running the diagnostic program and keying the PTT I get oscillations on the PTT relay in the
    Message 1 of 8 , May 5, 2009
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      I can manually short the PTT to Ground and all is well but when running the diagnostic program and keying the PTT I get oscillations on the PTT relay in the radio.

      Is the PTT circuit lacking the ability to handle the current needed to keep the PTT Relay engaged?

      Does L2 help protect the FET?
      or could it possibly be lowering the current running through the FET to the PTT output?

      Possible work around? Can the Power Relay be used to supply ground to the PTT Pin?

      The Radio is a 110 Watt RANGR with Modified Input Plug and everything checks out fine on the radio end.
    • Scott Miller
      How much current does it need? The 2N7002 can handle a fair amount for a little MOSFET. All of the ferrites on the board are there for RFI suppression. Will
      Message 2 of 8 , May 5, 2009
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        How much current does it need? The 2N7002 can handle a fair amount for
        a little MOSFET. All of the ferrites on the board are there for RFI
        suppression.

        Will it transmit if you use a 100 ohm resistor instead of a jumper wire?
        If so, can you try putting the 100 ohm resistor in line with the PTT
        on the tracker?

        Scott

        Rob wrote:
        >
        >
        >
        > I can manually short the PTT to Ground and all is well but when running
        > the diagnostic program and keying the PTT I get oscillations on the PTT
        > relay in the radio.
        >
        > Is the PTT circuit lacking the ability to handle the current needed to
        > keep the PTT Relay engaged?
        >
        > Does L2 help protect the FET?
        > or could it possibly be lowering the current running through the FET to
        > the PTT output?
        >
        > Possible work around? Can the Power Relay be used to supply ground to
        > the PTT Pin?
        >
        > The Radio is a 110 Watt RANGR with Modified Input Plug and everything
        > checks out fine on the radio end.
        >
        >
      • Rob
        Scott, Thanks for replying so quickly... I tried the 100ohm resistor in-line and did not help. I also Measured the current and its only like 10ma. I am
        Message 3 of 8 , May 6, 2009
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          Scott, Thanks for replying so quickly... I tried the 100ohm resistor in-line and did not help. I also Measured the current and its only like 10ma. I am going to double check my tracker2 with another radio and make sure something is not intermittent on the PTT could the software be detecting some type of audio or Squelch and not holding the PTT control signal steady on the controller side of things??



          --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
          >
          > How much current does it need? The 2N7002 can handle a fair amount for
          > a little MOSFET. All of the ferrites on the board are there for RFI
          > suppression.
          >
          > Will it transmit if you use a 100 ohm resistor instead of a jumper wire?
          > If so, can you try putting the 100 ohm resistor in line with the PTT
          > on the tracker?
          >
          > Scott
          >
          > Rob wrote:
          > >
          > >
          > >
          > > I can manually short the PTT to Ground and all is well but when running
          > > the diagnostic program and keying the PTT I get oscillations on the PTT
          > > relay in the radio.
          > >
          > > Is the PTT circuit lacking the ability to handle the current needed to
          > > keep the PTT Relay engaged?
          > >
          > > Does L2 help protect the FET?
          > > or could it possibly be lowering the current running through the FET to
          > > the PTT output?
          > >
          > > Possible work around? Can the Power Relay be used to supply ground to
          > > the PTT Pin?
          > >
          > > The Radio is a 110 Watt RANGR with Modified Input Plug and everything
          > > checks out fine on the radio end.
          > >
          > >
          >
        • Scott Miller
          ... In diagnostic mode, it just tells the tracker to turn PTT on, and the tracker turns on that pin. There s no other logic to it. I d check for possible RFI
          Message 4 of 8 , May 6, 2009
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            > sure something is not intermittent on the PTT could the software be
            > detecting some type of audio or Squelch and not holding the PTT control
            > signal steady on the controller side of things??

            In diagnostic mode, it just tells the tracker to turn PTT on, and the
            tracker turns on that pin. There's no other logic to it.

            I'd check for possible RFI problems. If you can, put the radio on its
            lowest power setting and keep the tracker away from the antenna.

            Scott
          • Rob
            ... Hmmm... RFI... maybe I should put the covers back on the radio. I am using a dummy load. And I also cranked the power down to almost minimum. But still
            Message 5 of 8 , May 6, 2009
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              --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
              Hmmm... RFI... maybe I should put the covers back on the radio.
              I am using a dummy load. And I also cranked the power down to almost minimum. But still this radio puts out quite a punch. I have some ferrite cores also.. Let my do some more testing... My cable going to the radio is also about 8 feet long. But it is shielded...
              Again thanks for the quick response...

              >
              > > sure something is not intermittent on the PTT could the software be
              > > detecting some type of audio or Squelch and not holding the PTT control
              > > signal steady on the controller side of things??
              >
              > In diagnostic mode, it just tells the tracker to turn PTT on, and the
              > tracker turns on that pin. There's no other logic to it.
              >
              > I'd check for possible RFI problems. If you can, put the radio on its
              > lowest power setting and keep the tracker away from the antenna.
              >
              > Scott
              >
            • Rob
              ... Not having any luck... I sealed up the radio.. added ferrite cores to cable. The easiest work around my be a small 12v relay. But not having a parts store
              Message 6 of 8 , May 6, 2009
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                --- In tracker2@yahoogroups.com, "Rob" <rhenry@...> wrote:
                Not having any luck...
                I sealed up the radio.. added ferrite cores to cable.
                The easiest work around my be a small 12v relay. But not having a parts store within 60 miles. I am going to have to wait or scavenge one out of some old equipment. Unless you have any other suggestions?

                >
                > --- In tracker2@yahoogroups.com, Scott Miller <scott@> wrote:
                > Hmmm... RFI... maybe I should put the covers back on the radio.
                > I am using a dummy load. And I also cranked the power down to almost minimum. But still this radio puts out quite a punch. I have some ferrite cores also.. Let my do some more testing... My cable going to the radio is also about 8 feet long. But it is shielded...
                > Again thanks for the quick response...
                >
                > >
                > > > sure something is not intermittent on the PTT could the software be
                > > > detecting some type of audio or Squelch and not holding the PTT control
                > > > signal steady on the controller side of things??
                > >
                > > In diagnostic mode, it just tells the tracker to turn PTT on, and the
                > > tracker turns on that pin. There's no other logic to it.
                > >
                > > I'd check for possible RFI problems. If you can, put the radio on its
                > > lowest power setting and keep the tracker away from the antenna.
                > >
                > > Scott
                > >
                >
              • Wes Freeman
                Hi Rob, How about trying this: Disconnect the radio and then measure the processor pin that drives the gate of the 2N7000. It should either be a steady 0V or
                Message 7 of 8 , May 6, 2009
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                  Hi Rob,

                  How about trying this:

                  Disconnect the radio and then measure the processor
                  pin that drives the gate of the 2N7000. It should
                  either be a steady 0V or 5V when you control it from
                  the config program.

                  Then connect the radio and measure again. If the voltages
                  are still steady, that should tell you it's not RFI.

                  You can also connect your 100 Ohm resistor from the 12V
                  supply (or whatever supply you're using for the Tracker) to
                  the PTT output of the Tracker. If the voltage swings from
                  12V to near zero Volts, then the 2N7000 is working.

                  BTW, did the radio transmit when you shorted PTT to ground
                  with the 100 Ohm resistor?

                  Cheers,

                  Wes Freeman
                  KG6POV

                  Rob wrote:
                  Scott,  Thanks for replying so quickly...  I tried the 100ohm resistor in-line and did not help.  I also Measured the current and its only like 10ma.  I am going to double check my tracker2 with another radio and make sure something is not intermittent on the PTT could the software be detecting some type of audio or Squelch and not holding the PTT control signal steady on the controller side of things??
                  
                  
                  
                  --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
                    
                  How much current does it need?  The 2N7002 can handle a fair amount for 
                  a little MOSFET.  All of the ferrites on the board are there for RFI 
                  suppression.
                  
                  Will it transmit if you use a 100 ohm resistor instead of a jumper wire? 
                    If so, can you try putting the 100 ohm resistor in line with the PTT 
                  on the tracker?
                  
                  Scott
                  
                  Rob wrote:
                      
                  
                  I can manually short the PTT to Ground and all is well but when running 
                  the diagnostic program and keying the PTT I get oscillations on the PTT 
                  relay in the radio.
                  
                  Is the PTT circuit lacking the ability to handle the current needed to 
                  keep the PTT Relay engaged?
                  
                  Does L2 help protect the FET?
                  or could it possibly be lowering the current running through the FET to 
                  the PTT output?
                  
                  Possible work around? Can the Power Relay be used to supply ground to 
                  the PTT Pin?
                  
                  The Radio is a 110 Watt RANGR with Modified Input Plug and everything 
                  checks out fine on the radio end.
                  
                  
                        
                  
                  
                  
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                • Rob
                  Hey you guys know that pin 9 on the serial connector looks like a six upside down..... LOL.... Sorry had Ground running to pin 9 instead of pin 6... All
                  Message 8 of 8 , May 6, 2009
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                    Hey you guys know that pin 9 on the serial connector looks like a six upside down..... LOL.... Sorry had Ground running to pin 9 instead of pin 6... All works now...
                    Thanks for you input...



                    --- In tracker2@yahoogroups.com, Wes Freeman <wes.freeman@...> wrote:
                    >
                    > Hi Rob,
                    >
                    > How about trying this:
                    >
                    > Disconnect the radio and then measure the processor
                    > pin that drives the gate of the 2N7000. It should
                    > either be a steady 0V or 5V when you control it from
                    > the config program.
                    >
                    > Then connect the radio and measure again. If the voltages
                    > are still steady, that should tell you it's not RFI.
                    >
                    > You can also connect your 100 Ohm resistor from the 12V
                    > supply (or whatever supply you're using for the Tracker) to
                    > the PTT output of the Tracker. If the voltage swings from
                    > 12V to near zero Volts, then the 2N7000 is working.
                    >
                    > BTW, did the radio transmit when you shorted PTT to ground
                    > with the 100 Ohm resistor?
                    >
                    > Cheers,
                    >
                    > Wes Freeman
                    > KG6POV
                    >
                    > Rob wrote:
                    >
                    > >Scott, Thanks for replying so quickly... I tried the 100ohm resistor in-line and did not help. I also Measured the current and its only like 10ma. I am going to double check my tracker2 with another radio and make sure something is not intermittent on the PTT could the software be detecting some type of audio or Squelch and not holding the PTT control signal steady on the controller side of things??
                    > >
                    > >
                    > >
                    > >--- In tracker2@yahoogroups.com, Scott Miller <scott@> wrote:
                    > >
                    > >
                    > >>How much current does it need? The 2N7002 can handle a fair amount for
                    > >>a little MOSFET. All of the ferrites on the board are there for RFI
                    > >>suppression.
                    > >>
                    > >>Will it transmit if you use a 100 ohm resistor instead of a jumper wire?
                    > >> If so, can you try putting the 100 ohm resistor in line with the PTT
                    > >>on the tracker?
                    > >>
                    > >>Scott
                    > >>
                    > >>Rob wrote:
                    > >>
                    > >>
                    > >>>
                    > >>>I can manually short the PTT to Ground and all is well but when running
                    > >>>the diagnostic program and keying the PTT I get oscillations on the PTT
                    > >>>relay in the radio.
                    > >>>
                    > >>>Is the PTT circuit lacking the ability to handle the current needed to
                    > >>>keep the PTT Relay engaged?
                    > >>>
                    > >>>Does L2 help protect the FET?
                    > >>>or could it possibly be lowering the current running through the FET to
                    > >>>the PTT output?
                    > >>>
                    > >>>Possible work around? Can the Power Relay be used to supply ground to
                    > >>>the PTT Pin?
                    > >>>
                    > >>>The Radio is a 110 Watt RANGR with Modified Input Plug and everything
                    > >>>checks out fine on the radio end.
                    > >>>
                    > >>>
                    > >>>
                    > >>>
                    > >
                    > >
                    > >
                    > >
                    > >------------------------------------
                    > >
                    > >Yahoo! Groups Links
                    > >
                    > >
                    > >
                    > >
                    > >
                    > >
                    >
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