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RXTX No Transmit--Looking For Help

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  • jnfritz07
    I purchased a used Softrock Ensemble RXTX from another ham who indicated that the unit received well but did not transmit. He was true to his word.  I have
    Message 1 of 16 , Jun 28, 2013
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      I purchased a used Softrock Ensemble RXTX from another ham who indicated that the unit received well but did not transmit. He was true to his word. 

      I have carefully checked most of the unit over and done a fair amount of troubleshooting. From this I know that the RX/TX switching circuitry is acting as it should. All the switching component voltages are what they should be for both transmit and receive. I get all the correct voltages including the 8 volts on the junction of R50 and R51 which does follow the transmit toggling on HDSDR. 

      However, there is still no output in transmit and no hint of a signal on a Kenwood transceiver located right next to the RXTX. Using the terrific on-line guide by WB5RVZ I have checked voltages in the RF transmitter sections. I haven't exhausted every single test, but I have run checks until my eyes are crossed and can't find the cause.

      I can continue checking, but if someone has some hints for obvious places to look or test for where things have gone wrong in the transmitter section, that would be very much appreciated. 

      I am open to any and all suggestions. 

      73,

      Jeff, WB1AAL
    • Dave Matthews
      Check the output level on the sound card. I have been bitten by that before. Dave W2IJL
      Message 2 of 16 , Jun 28, 2013
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        Check the output level on the sound card.  I have been bitten by that before.

        Dave
        W2IJL


        On Fri, Jun 28, 2013 at 5:57 PM, jnfritz07 <jnfritz07@...> wrote:
         

        I purchased a used Softrock Ensemble RXTX from another ham who indicated that the unit received well but did not transmit. He was true to his word. 

        I have carefully checked most of the unit over and done a fair amount of troubleshooting. From this I know that the RX/TX switching circuitry is acting as it should. All the switching component voltages are what they should be for both transmit and receive. I get all the correct voltages including the 8 volts on the junction of R50 and R51 which does follow the transmit toggling on HDSDR. 

        However, there is still no output in transmit and no hint of a signal on a Kenwood transceiver located right next to the RXTX. Using the terrific on-line guide by WB5RVZ I have checked voltages in the RF transmitter sections. I haven't exhausted every single test, but I have run checks until my eyes are crossed and can't find the cause.

        I can continue checking, but if someone has some hints for obvious places to look or test for where things have gone wrong in the transmitter section, that would be very much appreciated. 

        I am open to any and all suggestions. 

        73,

        Jeff, WB1AAL


      • Alan
        ... Subject: [softrock40] RXTX No Transmit--Looking For Help ... Jeff, I guess you tuned around and heard the LO at the centre but nothing else? Make sure you
        Message 3 of 16 , Jun 28, 2013
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          ----- Original Message -----
          Subject: [softrock40] RXTX No Transmit--Looking For Help


          >However, there is still no output in transmit and no hint of a signal on a Kenwood transceiver located right next to the RXTX.
          >Using the terrific on-line guide by WB5RVZ I have checked voltages in the RF transmitter sections. I haven't exhausted every single
          >test, but I have run checks until my eyes are crossed and can't find the cause.

          Jeff,

          I guess you tuned around and heard the LO at the centre but nothing else?

          Make sure you do have audio going in to it, mixer settings, cable.
          <https://sites.google.com/site/g4zfqradio/levels-measured-in-a-softrock-tx> gives some idea on signal levels and how to check them.

          73 Alan G4ZFQ
        • km5ht
          I use HDSDR. Put a dummy load on the output and set HDSDR to FM. You can measure the output at the antenna jack with a scope or rf probe. I built this one
          Message 4 of 16 , Jun 29, 2013
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            I use HDSDR. Put a dummy load on the output and set HDSDR to FM. You can measure the output at the antenna jack with a scope or rf probe. I built this one and use it with a fluke digital multimeter. http://www.n5ese.com/rfprobe2.htm

            Good luck and 73
            KM5HT

            --- In softrock40@yahoogroups.com, "jnfritz07" <jnfritz07@...> wrote:
            >
            > I purchased a used Softrock Ensemble RXTX from another ham who indicated that the unit received well but did not transmit. He was true to his word. 
            >
            > I have carefully checked most of the unit over and done a fair amount of troubleshooting. From this I know that the RX/TX switching circuitry is acting as it should. All the switching component voltages are what they should be for both transmit and receive. I get all the correct voltages including the 8 volts on the junction of R50 and R51 which does follow the transmit toggling on HDSDR. 
            >
            > However, there is still no output in transmit and no hint of a signal on a Kenwood transceiver located right next to the RXTX. Using the terrific on-line guide by WB5RVZ I have checked voltages in the RF transmitter sections. I haven't exhausted every single test, but I have run checks until my eyes are crossed and can't find the cause.
            >
            > I can continue checking, but if someone has some hints for obvious places to look or test for where things have gone wrong in the transmitter section, that would be very much appreciated. 
            >
            > I am open to any and all suggestions. 
            >
            > 73,
            >
            > Jeff, WB1AAL
            >
          • jnfritz07
            Excellent suggestion, Dave. I ll give that a try. Thanks! 73, Jeff, WB1AAL
            Message 5 of 16 , Jun 29, 2013
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              Excellent suggestion, Dave. I'll give that a try. Thanks!

              73,

              Jeff, WB1AAL

              --- In softrock40@yahoogroups.com, Dave Matthews <n36078@...> wrote:
              >
              > Check the output level on the sound card. I have been bitten by that
              > before.
              >
              > Dave
              > W2IJL
            • jnfritz07
              I can t even hear the LO, Alan, and I have no signal or output even in CW mode with the paddle input shorted. I don t think that the transmitter RF stages are
              Message 6 of 16 , Jun 29, 2013
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                I can't even hear the LO, Alan, and I have no signal or output even in CW mode with the paddle input shorted. I don't think that the transmitter RF stages are working, but as I told Dave, I still need to check the audio levels into the RXTX. I didnt think that audio level would matter in CW mode, but I am still learning about SDR radios so I could easily be mistaken.

                73,

                Jeff, WB1AAL

                --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                >
                > I guess you tuned around and heard the LO at the centre but nothing else?
                >
                > Make sure you do have audio going in to it, mixer settings, cable.
                > <https://sites.google.com/site/g4zfqradio/levels-measured-in-a-softrock-tx> gives some idea on signal levels and how to check them.
                >
                > 73 Alan G4ZFQ
                >
              • jnfritz07
                Thanks very much for the suggestion. I have a working low power wattmeter, so I did as you suggested. I put HDSDR in FM mode and put the wattmeter and dummy
                Message 7 of 16 , Jun 29, 2013
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                  Thanks very much for the suggestion. I have a working low power wattmeter, so I did as you suggested. I put HDSDR in FM mode and put the wattmeter and dummy load on the RXTX. There was no output. Measuring at the BNC show zero AC voktage as well.

                  73,

                  Jeff, WB1AAL

                  --- In softrock40@yahoogroups.com, "km5ht" <km5ht@...> wrote:
                  >
                  > I use HDSDR. Put a dummy load on the output and set HDSDR to FM. You can measure the output at the antenna jack with a scope or rf probe. I built this one and use it with a fluke digital multimeter. http://www.n5ese.com/rfprobe2.htm
                  >
                  > Good luck and 73
                  > KM5HT
                • Alan
                  ... Subject: [softrock40] Re: RXTX No Transmit--Looking For Help ... Jeff, The LO is always heard at a low level. At the LO frequency. If you do not hear it
                  Message 8 of 16 , Jun 29, 2013
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                    ----- Original Message -----
                    Subject: [softrock40] Re: RXTX No Transmit--Looking For Help


                    >I can't even hear the LO, Alan, and I have no signal or output even in CW mode with the paddle input shorted. I don't think that
                    >the transmitter RF stages are working, but as I told Dave, I still need to check the audio levels into the RXTX. I didnt think that
                    >audio level would matter in CW mode, but I am still learning about SDR radios so I could easily be mistaken.
                    >

                    Jeff,

                    The LO is always heard at a low level. At the LO frequency. If you do not hear it check the LO. Does it receive properly?
                    Audio is what drives SDRs, whatever mode. CW, a single tone. Well two tones, IQ 90° apart.

                    73 Alan G4ZFQ
                  • jnfritz07
                    Excellent, excellent suggestions and help! Thanks so very much to everyone who responded to my cry for help on the RXTX that won t transmit. Your help and
                    Message 9 of 16 , Jun 29, 2013
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                      Excellent, excellent suggestions and help! Thanks so very much to everyone who responded to my cry for help on the RXTX that won't transmit. Your help and input is appreciated!

                      In looking into the no transmit issue further, I did find two missing components in the transmitter section (a 220 pf cap and a 68.1 K Ohm resistor off of the emitter of Q6.) I added them back in the circuit but that wasn't the issue. In fact, the original builder who sold me the RXTX told me that those are not supposed to be there for the 40-30-20 meter RXTX. Should I remove these?

                      73,

                      Jeff, WB1AAL
                    • Alan
                      ... Subject: [softrock40] Re: RXTX No Transmit--Looking For Help ... Jeff, Robby s pages will tell you this. But in any case they will not make much
                      Message 10 of 16 , Jun 29, 2013
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                        ----- Original Message -----
                        Subject: [softrock40] Re: RXTX No Transmit--Looking For Help


                        > In looking into the no transmit issue further, I did find two missing components in the transmitter section (a 220 pf cap and a
                        > 68.1 K Ohm resistor off of the emitter of Q6.) I added them back in the circuit but that wasn't the issue. In fact, the original
                        > builder who sold me the RXTX told me that those are not supposed to be there for the 40-30-20 meter RXTX. Should I remove these?
                        >

                        Jeff,

                        Robby's pages will tell you this.
                        But in any case they will not make much difference.

                        73 Alan G4ZFQ
                      • jnfritz07
                        The receiver works very well, Alan. It is sensitive, tunable and works on all three bands (40, 30 and 20 meters.) It is now time to work from your excellent
                        Message 11 of 16 , Jun 29, 2013
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                          The receiver works very well, Alan. It is sensitive, tunable and works on all three bands (40, 30 and 20 meters.) It is now time to work from your excellent audio troubleshooting page, but first perhaps you can help with a translation about voltages.

                          For example, your page says, "Audio voltages may be measured at the hairpins of R26, 25, 28, and 27. For 500mW out I measured about 1V2 peak-peak on an oscilloscope and about 0V5 RMS with a digital meter."

                          The voltage format is throwing me because we don't use that here. Is 1V2 equivalent to what we would describe as 1.2 volts? Similarly is 0V5 the same as 0.5 volts?

                          Many thanks and 73,

                          Jeff, WB1AAL

                          --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:

                          > Jeff,
                          >
                          > The LO is always heard at a low level. At the LO frequency. If you do not hear it check the LO. Does it receive properly?
                          > Audio is what drives SDRs, whatever mode. CW, a single tone. Well two tones, IQ 90° apart.
                          >
                          > 73 Alan G4ZFQ
                        • jnfritz07
                          Got it, Alan. Thanks! 73, Jeff, WB1AAL
                          Message 12 of 16 , Jun 29, 2013
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                            Got it, Alan. Thanks!

                            73,

                            Jeff, WB1AAL

                            > Jeff,
                            >
                            > Robby's pages will tell you this.
                            > But in any case they will not make much difference.
                            >
                            > 73 Alan G4ZFQ
                          • Alan
                            ... Subject: [softrock40] Re: RXTX No Transmit--Looking For Help ... Jeff, But you can not hear the LO with a RX when you TX? ... Yes, it saves typing. A
                            Message 13 of 16 , Jun 29, 2013
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                              ----- Original Message -----
                              Subject: [softrock40] Re: RXTX No Transmit--Looking For Help


                              >The receiver works very well, Alan. It is sensitive, tunable and works on all three bands (40, 30 and 20 meters.)

                              Jeff,

                              But you can not hear the LO with a RX when you TX?

                              >The voltage format is throwing me because we don't use that here. Is 1V2 equivalent to what we would describe as 1.2 volts?
                              >Similarly is 0V5 the same as 0.5 volts?

                              Yes, it saves typing. A fairly common format, 1A0 one amp, 1R0 ...

                              73 Alan G4ZFQ
                            • jnfritz07
                              Alan has been kindly and diligently working with me on the no transmit issue with my used Softrock Ensemble RXTX. (Thank you so much, Alan!) We have tried a
                              Message 14 of 16 , Jun 30, 2013
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                                Alan has been kindly and diligently working with me on the no transmit issue with my used Softrock Ensemble RXTX. (Thank you so much, Alan!)

                                We have tried a number of things to sort this out and everything points to an issue in the RF I/O Switching circuitry. However, at this point, it is time for a dose of reality.

                                I thought that I might find an obvious building mistake, fix it and have a nice QRP transceiver. (I've fixed building errors on other kits and wound up with some rather nice gear.) However, the time and effort that this is taking is not worth the intended use.

                                I bought the Softrock Ensemble RXTX primarily to learn about SDR and have an SDR 40 and 20 meter receiver to play with--which is why I wasn't put off by the seller saying that he could never get the board to transmit.

                                I consider myself lucky because will all of my messing around, shorting things, cutting things, etc. the receiver still works perfectly. Therefore, I am not going to press my luck any further and risk damaging the receiver. So, at this point, I am going to be content to use it as a very nice SDR ham band receiver.

                                But I am not going to do this without first thanking the Yahoo Softrock group for all your insight, patience and very great help. I sincerely appreciate your assistance to me!

                                Thank you again!

                                73,

                                Jeff, WB1AAL
                              • ejfelix4976
                                Hi Jeff, Sorry to hear your giving up. Did you probe pins 3,4,5,6 of the QSE chip with an oscope ?? If you feed in a signal from HDSDR you should see sine
                                Message 15 of 16 , Jun 30, 2013
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                                  Hi Jeff,
                                  Sorry to hear your giving up.
                                  Did you probe pins 3,4,5,6 of the QSE chip with an oscope ??
                                  If you feed in a signal from HDSDR you should see sine waves
                                  At these pins.
                                  Be sure your scope ground is on the 12v gnd and not the USB gnd.

                                  If not probe pin 2 of both u6 and u7 opamps.
                                  This comes right out of the jack.
                                  If you get signal there check pins 1 and 7.
                                  You should see the same signal level as on pin 2 as they are in unity gain.

                                  I once had a faulty jack that really had me going, check signal
                                  Right out of the jack.

                                  If you have signal on pins 3,4,5,6 of the QSE check pins 7 and 9.
                                  If you get a strange waveform, look at T2, it may be mis wound or
                                  Installed incorrectly.
                                  If you get no signal out of 7 and 9 check pins 1 and 15.
                                  During transmit these should be low ( no voltage) the chip is disabled
                                  If 1 and 15 are high.
                                  Hope this helps.
                                  Good luck

                                  Ed



                                  --- In softrock40@yahoogroups.com, "jnfritz07" <jnfritz07@...> wrote:
                                  >
                                  > Alan has been kindly and diligently working with me on the no transmit issue with my used Softrock Ensemble RXTX. (Thank you so much, Alan!)
                                  >
                                  > We have tried a number of things to sort this out and everything points to an issue in the RF I/O Switching circuitry. However, at this point, it is time for a dose of reality.
                                  >
                                  > I thought that I might find an obvious building mistake, fix it and have a nice QRP transceiver. (I've fixed building errors on other kits and wound up with some rather nice gear.) However, the time and effort that this is taking is not worth the intended use.
                                  >
                                  > I bought the Softrock Ensemble RXTX primarily to learn about SDR and have an SDR 40 and 20 meter receiver to play with--which is why I wasn't put off by the seller saying that he could never get the board to transmit.
                                  >
                                  > I consider myself lucky because will all of my messing around, shorting things, cutting things, etc. the receiver still works perfectly. Therefore, I am not going to press my luck any further and risk damaging the receiver. So, at this point, I am going to be content to use it as a very nice SDR ham band receiver.
                                  >
                                  > But I am not going to do this without first thanking the Yahoo Softrock group for all your insight, patience and very great help. I sincerely appreciate your assistance to me!
                                  >
                                  > Thank you again!
                                  >
                                  > 73,
                                  >
                                  > Jeff, WB1AAL
                                  >
                                • Alan
                                  ... Subject: [softrock40] Re: RXTX No Transmit--Looking For Help ... Ed, We had got to the point of finding that S12V was high with Q3 removed. As it was still
                                  Message 16 of 16 , Jun 30, 2013
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                                    ----- Original Message -----
                                    Subject: [softrock40] Re: RXTX No Transmit--Looking For Help


                                    > Did you probe pins 3,4,5,6 of the QSE chip with an oscope ??

                                    Ed,

                                    We had got to the point of finding that S12V was high with Q3 removed.
                                    As it was still receiving Jeff decided to stop.
                                    I was hoping another six email exchanges would be enough. Maybe in a little while he will have another go.

                                    73 Alan G4ZFQ
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