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Re: To match or not to match... BS170s in your RXTX

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  • Taka Sugi
    Hello Warren Yes I agree with you, Q5 variability affects Bias voltage. Especially,Vth variability. ‡™Vbias/‡™Vth is about 1.0 ! If Vth@changes
    Message 1 of 19 , Nov 29, 2012
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      Hello Warren

      Yes I agree with you, Q5 variability affects Bias voltage. Especially,Vth variability. ‡™Vbias/‡™Vth is about 1.0 ! If Vth@changes 0.2V, then Vbias changes 0.2V.
      I mentioned before on this message board, I replaced R41(33.2ohm)
      by 50 ohm trimmer for tuning "initial bias voltage/idle current of Q7/Q8" , to remove variability of Q5.

      I selected pair BS170s:Q7/Q8 and tuned idle current 25mA for my
      Ensemble 40/30/20m, and measured IMD3. IMD3 is as follows,...

      PEP(w)@ 40m 30m 20m
      0.1 43dB 41dB 44dB
      0.3 41 38 33
      0.5 39 36 28
      0.7 37 34 26
      1.0 35 32 22

      I usually use less than 0.7W PEP.

      73, JA1TLH/Taka

      > Hi Taka
      >
      > I agree with you partially and I answered somewhat in my post to Alan. I think you are absolutely that the output power-temperature dependence will change somewhat. However, because this is in effect a high gain negative feedback loop it will tend to stabilize.
      >
      > What I have found is initial bias voltage is very dependent upon the selection of the Q5 device. As I mentioned in my reply to Alan, there is a very close correlation between the initial bias voltage and the final power output. It would seem there is a significant variance in the drain-source conductivity among devices for a given gate voltage.
      >
      > That is my guess.... i need more work to verify. Thank you for your reply and let us chat more later when I have time.
      >
      > Regards,
      >
      > Warren Allgyer
    • warrenallgyer
      Hello Taka Congratulations on your excellent IMD3 results. I see you start to have a little bit of problem on 20 meters. I too have noticed this and my
      Message 2 of 19 , Nov 29, 2012
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        Hello Taka

        Congratulations on your excellent IMD3 results. I see you start to have a little bit of problem on 20 meters. I too have noticed this and my 30/20/17 build shows even worse performance on 17 meters where I can find no power level that gives better than 20 dB for IMD3.

        Alan has begun some research which indicates the driver stage may be introducing distortion at 17 and maybe at 20 as well. He is measuring this by using a scope probe to the RXII receiver and checking the driver input versus output. I have not had a chance to verify that my driver also has a problem but I suspect it does. I am wondering if this is something that begins to show at 20 meters.

        This is one more thing I intend to investigate when I return home.

        I like your idea of a 50 ohm trimmer for R41 and I plan to look for suitable components to convert my radios as well. I think this is much better than swapping different devices in the Q5 position.

        Best regards,

        Warren Allgyer - W8TOD
        (now operating temporarily from the home QTH in Ohio)

        --- In softrock40@yahoogroups.com, "Taka Sugi" <taka_sugi1206@...> wrote:
        >
        >
        >
        >
        > Hello Warren
        >
        > Yes I agree with you, Q5 variability affects Bias voltage. Especially,Vth variability. ‡™Vbias/‡™Vth is about 1.0 ! If Vth@changes 0.2V, then Vbias changes 0.2V.
        > I mentioned before on this message board, I replaced R41(33.2ohm)
        > by 50 ohm trimmer for tuning "initial bias voltage/idle current of Q7/Q8" , to remove variability of Q5.
        >
        > I selected pair BS170s:Q7/Q8 and tuned idle current 25mA for my
        > Ensemble 40/30/20m, and measured IMD3. IMD3 is as follows,...
        >
        > PEP(w)@ 40m 30m 20m
        > 0.1 43dB 41dB 44dB
        > 0.3 41 38 33
        > 0.5 39 36 28
        > 0.7 37 34 26
        > 1.0 35 32 22
        >
        > I usually use less than 0.7W PEP.
        >
        > 73, JA1TLH/Taka
        >
        > > Hi Taka
        > >
        > > I agree with you partially and I answered somewhat in my post to Alan. I think you are absolutely that the output power-temperature dependence will change somewhat. However, because this is in effect a high gain negative feedback loop it will tend to stabilize.
        > >
        > > What I have found is initial bias voltage is very dependent upon the selection of the Q5 device. As I mentioned in my reply to Alan, there is a very close correlation between the initial bias voltage and the final power output. It would seem there is a significant variance in the drain-source conductivity among devices for a given gate voltage.
        > >
        > > That is my guess.... i need more work to verify. Thank you for your reply and let us chat more later when I have time.
        > >
        > > Regards,
        > >
        > > Warren Allgyer
        >
      • KQ8M
        Warren, Where are you in Ohio? I am on the east side of Cleveland. 73, Tim Herrick, KQ8M Charter Member North Coast Contesters kq8m@kq8m.com AR-Cluster V6
        Message 3 of 19 , Nov 29, 2012
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          Warren,

           

          Where are you in Ohio? I am on the east side of Cleveland.

           

          73,

          Tim Herrick, KQ8M

          Charter Member North Coast Contesters

          kq8m@...

           

          AR-Cluster V6 kq8m.no-ip.org

          User Ports: 23, 7373  with local skimmer, 7374 without local skimmer

          Server Ports: V6 3607, V4 Active 3605, V4 Passive 3606

           

          From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of warrenallgyer
          Sent: Friday, November 30, 2012 1:37 AM
          To: softrock40@yahoogroups.com
          Subject: [softrock40] Re: To match or not to match... BS170s in your RXTX

           

           


          Hello Taka

          Congratulations on your excellent IMD3 results. I see you start to have a little bit of problem on 20 meters. I too have noticed this and my 30/20/17 build shows even worse performance on 17 meters where I can find no power level that gives better than 20 dB for IMD3.

          Alan has begun some research which indicates the driver stage may be introducing distortion at 17 and maybe at 20 as well. He is measuring this by using a scope probe to the RXII receiver and checking the driver input versus output. I have not had a chance to verify that my driver also has a problem but I suspect it does. I am wondering if this is something that begins to show at 20 meters.

          This is one more thing I intend to investigate when I return home.

          I like your idea of a 50 ohm trimmer for R41 and I plan to look for suitable components to convert my radios as well. I think this is much better than swapping different devices in the Q5 position.

          Best regards,

          Warren Allgyer - W8TOD
          (now operating temporarily from the home QTH in Ohio)

          --- In softrock40@yahoogroups.com, "Taka Sugi" <taka_sugi1206@...> wrote:
          >
          >
          >
          >
          > Hello Warren
          >
          > Yes I agree with you, Q5 variability affects Bias voltage. Especially,Vth variability. ‡™Vbias/‡™Vth is about 1.0 ! If Vth@changes 0.2V, then Vbias changes 0.2V.
          > I mentioned before on this message board, I replaced R41(33.2ohm)
          > by 50 ohm trimmer for tuning "initial bias voltage/idle current of Q7/Q8" , to remove variability of Q5.
          >
          > I selected pair BS170s:Q7/Q8 and tuned idle current 25mA for my
          > Ensemble 40/30/20m, and measured IMD3. IMD3 is as follows,...
          >
          > PEP(w)@ 40m 30m 20m
          > 0.1 43dB 41dB 44dB
          > 0.3 41 38 33
          > 0.5 39 36 28
          > 0.7 37 34 26
          > 1.0 35 32 22
          >
          > I usually use less than 0.7W PEP.
          >
          > 73, JA1TLH/Taka
          >
          > > Hi Taka
          > >
          > > I agree with you partially and I answered somewhat in my post to Alan. I think you are absolutely that the output power-temperature dependence will change somewhat. However, because this is in effect a high gain negative feedback loop it will tend to stabilize.
          > >
          > > What I have found is initial bias voltage is very dependent upon the selection of the Q5 device. As I mentioned in my reply to Alan, there is a very close correlation between the initial bias voltage and the final power output. It would seem there is a significant variance in the drain-source conductivity among devices for a given gate voltage.
          > >
          > > That is my guess.... i need more work to verify. Thank you for your reply and let us chat more later when I have time.
          > >
          > > Regards,
          > >
          > > Warren Allgyer
          >

        • warrenallgyer
          Hi Tim I am in Gnadenhutten, OH. About 100 miles south of you on I77 Warren Allgyer -W8TOD
          Message 4 of 19 , Nov 30, 2012
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            Hi Tim

            I am in Gnadenhutten, OH. About 100 miles south of you on I77

            Warren Allgyer -W8TOD

            --- In softrock40@yahoogroups.com, "KQ8M" <kq8m@...> wrote:
            >
            > Warren,
            >
            >
            >
            > Where are you in Ohio? I am on the east side of Cleveland.
            >
            >
            >
            > 73,
            >
            > Tim Herrick, KQ8M
            >
            > Charter Member North Coast Contesters
            >
            > kq8m@...
            >
            >
            >
            > AR-Cluster V6 kq8m.no-ip.org
            >
            > User Ports: 23, 7373 with local skimmer, 7374 without local skimmer
            >
            > Server Ports: V6 3607, V4 Active 3605, V4 Passive 3606
            >
            >
            >
            > From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of warrenallgyer
            > Sent: Friday, November 30, 2012 1:37 AM
            > To: softrock40@yahoogroups.com
            > Subject: [softrock40] Re: To match or not to match... BS170s in your RXTX
            >
            >
            >
            >
            >
            >
            > Hello Taka
            >
            > Congratulations on your excellent IMD3 results. I see you start to have a little bit of problem on 20 meters. I too have noticed this and my 30/20/17 build shows even worse performance on 17 meters where I can find no power level that gives better than 20 dB for IMD3.
            >
            > Alan has begun some research which indicates the driver stage may be introducing distortion at 17 and maybe at 20 as well. He is measuring this by using a scope probe to the RXII receiver and checking the driver input versus output. I have not had a chance to verify that my driver also has a problem but I suspect it does. I am wondering if this is something that begins to show at 20 meters.
            >
            > This is one more thing I intend to investigate when I return home.
            >
            > I like your idea of a 50 ohm trimmer for R41 and I plan to look for suitable components to convert my radios as well. I think this is much better than swapping different devices in the Q5 position.
            >
            > Best regards,
            >
            > Warren Allgyer - W8TOD
            > (now operating temporarily from the home QTH in Ohio)
            >
            > --- In softrock40@yahoogroups.com <mailto:softrock40%40yahoogroups.com> , "Taka Sugi" <taka_sugi1206@> wrote:
            > >
            > >
            > >
            > >
            > > Hello Warren
            > >
            > > Yes I agree with you, Q5 variability affects Bias voltage. Especially,Vth variability. ‡™Vbias/‡™Vth is about 1.0 ! If Vth@changes 0.2V, then Vbias changes 0.2V.
            > > I mentioned before on this message board, I replaced R41(33.2ohm)
            > > by 50 ohm trimmer for tuning "initial bias voltage/idle current of Q7/Q8" , to remove variability of Q5.
            > >
            > > I selected pair BS170s:Q7/Q8 and tuned idle current 25mA for my
            > > Ensemble 40/30/20m, and measured IMD3. IMD3 is as follows,...
            > >
            > > PEP(w)@ 40m 30m 20m
            > > 0.1 43dB 41dB 44dB
            > > 0.3 41 38 33
            > > 0.5 39 36 28
            > > 0.7 37 34 26
            > > 1.0 35 32 22
            > >
            > > I usually use less than 0.7W PEP.
            > >
            > > 73, JA1TLH/Taka
            > >
            > > > Hi Taka
            > > >
            > > > I agree with you partially and I answered somewhat in my post to Alan. I think you are absolutely that the output power-temperature dependence will change somewhat. However, because this is in effect a high gain negative feedback loop it will tend to stabilize.
            > > >
            > > > What I have found is initial bias voltage is very dependent upon the selection of the Q5 device. As I mentioned in my reply to Alan, there is a very close correlation between the initial bias voltage and the final power output. It would seem there is a significant variance in the drain-source conductivity among devices for a given gate voltage.
            > > >
            > > > That is my guess.... i need more work to verify. Thank you for your reply and let us chat more later when I have time.
            > > >
            > > > Regards,
            > > >
            > > > Warren Allgyer
            > >
            >
          • warrenallgyer
            Hi Taka Here is what I see in this circuit: There is a long voltage divider chain from the 12V rail consisting of Q3, R37(22.1K),Q5, and R41(33.2). As Q5 is
            Message 5 of 19 , Nov 30, 2012
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              Hi Taka

              Here is what I see in this circuit:

              There is a long voltage divider chain from the 12V rail consisting of Q3, R37(22.1K),Q5, and R41(33.2). As Q5 is driven more and more into conduction by heat from the Q5/Q7/Q8 combo two things happen:

              1) As discussed, current through Q5 drives Q4 and effectively reduces the resistance of R40. This lowers the bias level on the finals.

              2) The increased current through Q5 also increases the voltage drop across R37 which reduces the collector voltage on Q6, the 2n2222 driver. This reduces the drive level to the finals, reducing the power output.

              So variances in Q5 produce big variances in the Q6 drive level as well as the operating point of the finals. This is why the Q5 circuitry is so effective at stabilizing the finals and why a choice here affects the power performance of the radio.

              This is my analysis. Do you agree?

              Warren Allgyer - W8TOD

              --- In softrock40@yahoogroups.com, "Taka Sugi" <taka_sugi1206@...> wrote:
              >
              >
              >
              >
              >
              >
              > Hi Warren
              >
              > I don't understand why Q5 dramatically affects output power.
              > Because, Q5/Q4 circuit works as constant voltage circuit to feed bias voltage to PA: Q7,Q8.
              > Q5 and Q7/Q8 are thermally connected, if Q5 is different maker/lot from Q7/Q8, then output power-temperature dependence will be changed.
              >
            • KF4BQ
              ... Hi Warren, Some bias point operation and other issues discussed at: http://groups.yahoo.com/group/softrock40/message/55570 73, Mike Collins KF4BQ
              Message 6 of 19 , Nov 30, 2012
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                --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:
                >
                > So variances in Q5 produce big variances in the Q6 drive level as well as the operating point of the finals. This is why the Q5 circuitry is so effective at stabilizing the finals and why a choice here affects the power performance of the radio.
                >
                > This is my analysis. Do you agree?
                >

                Hi Warren,

                Some bias point operation and other issues discussed at:
                http://groups.yahoo.com/group/softrock40/message/55570

                73, Mike Collins KF4BQ
              • Taka Sugi
                Hi Warren Yes, almost I agree. ... 1. Ib(Q4)= Id(Q5) - Vbe(Q4)/R41 Here Vbe(Q4) is about 0.6V 2. Ic(Q4)=hfe(Q4) x Ib(Q4) 3. Vbias= V1 - (R39 xIc(Q4) + Vd(D3))
                Message 7 of 19 , Dec 2, 2012
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                  Hi Warren

                  Yes, almost I agree.

                  > 1) As discussed, current through Q5 drives Q4 and effectively
                  >reduces the resistance of R40. This lowers the bias level on
                  >the finals.

                  1. Ib(Q4)= Id(Q5) - Vbe(Q4)/R41
                  Here Vbe(Q4) is about 0.6V
                  2. Ic(Q4)=hfe(Q4) x Ib(Q4)
                  3. Vbias= V1 - (R39 xIc(Q4) + Vd(D3))
                  Here V1= S12v - (R37 xIbias-circuit + Ic(Q6))
                  If Id(Q5) is increased, then Ic(Q4) is increased, as a result
                  Vbias is decreased( goes down).

                  If Id(Q7,Q8) goes up by temperature, then Id(Q5, thermally connected
                  to Q7,Q8) also goes up and Vbias goes down, then Id(Q7,Q8) goes down.
                  This is a kind of "feedback".
                  I am not sure about the function of R40(22.1k-ohm),but I think this
                  is to avoide "local oscillation"?

                  > 2) The increased current through Q5 also increases the voltage
                  > drop across R37 which reduces the collector voltage on Q6, the
                  >2n2222 driver. This reduces the drive level to the finals, reducing
                  >the power output.
                  > So variances in Q5 produce big variances in the Q6 drive level as
                  >well as the operating point of the finals. This is why the Q5
                  >circuitry is so effective at stabilizing the finals and why a
                  >choice here affects the power performance of the radio.
                  >
                  > This is my analysis. Do you agree?

                  I think there is little influence to Ic of driver Tr:Q6(2N2222),
                  unless Q5 varies drastically, because R37 is small ( 22.1 ohm).

                  JA1TLH/Taka
                • Alan
                  ... Subject: [softrock40] Re: To match or not to match... BS170s in your RXTX Taka, Did you read this? http://groups.yahoo.com/group/softrock40/message/55570
                  Message 8 of 19 , Dec 3, 2012
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                    ----- Original Message -----
                    Subject: [softrock40] Re: To match or not to match... BS170s in your RXTX


                    Taka,

                    Did you read this? http://groups.yahoo.com/group/softrock40/message/55570

                    Mike points out that Q4 maintains a constant current through R41 and therefore through Q5.
                    The current is constant in Q5, what varies is the voltage across it.
                    This is passed to Q7/8 through D3.
                    Q4 just maintains the constant current.

                    Mike, are you there?

                    73 Alan G4ZFQ



                    > Yes, almost I agree.
                    >
                    >> 1) As discussed, current through Q5 drives Q4 and effectively
                    >>reduces the resistance of R40. This lowers the bias level on
                    >>the finals.
                    >
                    > 1. Ib(Q4)= Id(Q5) - Vbe(Q4)/R41
                    > Here Vbe(Q4) is about 0.6V
                    > 2. Ic(Q4)=hfe(Q4) x Ib(Q4)
                    > 3. Vbias= V1 - (R39 xIc(Q4) + Vd(D3))
                    > Here V1= S12v - (R37 xIbias-circuit + Ic(Q6))
                    > If Id(Q5) is increased, then Ic(Q4) is increased, as a result
                    > Vbias is decreased( goes down).
                    >
                    > If Id(Q7,Q8) goes up by temperature, then Id(Q5, thermally connected
                    > to Q7,Q8) also goes up and Vbias goes down, then Id(Q7,Q8) goes down.
                    > This is a kind of "feedback".
                    > I am not sure about the function of R40(22.1k-ohm),but I think this
                    > is to avoide "local oscillation"?
                    >
                    >> 2) The increased current through Q5 also increases the voltage
                    >> drop across R37 which reduces the collector voltage on Q6, the
                    >>2n2222 driver. This reduces the drive level to the finals, reducing
                    >>the power output.
                    >> So variances in Q5 produce big variances in the Q6 drive level as
                    >>well as the operating point of the finals. This is why the Q5
                    >>circuitry is so effective at stabilizing the finals and why a
                    >>choice here affects the power performance of the radio.
                    >>
                    >> This is my analysis. Do you agree?
                    >
                    > I think there is little influence to Ic of driver Tr:Q6(2N2222),
                    > unless Q5 varies drastically, because R37 is small ( 22.1 ohm).
                  • Taka Sugi
                    Hi Alan ... Yes, I knew. I analyed before and also simulated@by@LTspice. If you have an interest pse refer to...
                    Message 9 of 19 , Dec 4, 2012
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                      Hi Alan
                      > Did you read this? http://groups.yahoo.com/group/softrock40/message/55570

                      Yes, I knew.
                      I analyed before and also simulated@by@LTspice.
                      If you have an interest pse refer to...

                      http://dl.dropbox.com/u/85347415/HAM/temp/PA_Bias%20Circuit.doc

                      JA1TLH/Taka
                    • Alan
                      ... Subject: [softrock40] Re: To match or not to match... BS170s in your RXTX Sorry Taka, I am too dumb to understand. But finally I see. I need simple
                      Message 10 of 19 , Dec 4, 2012
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                        ----- Original Message -----
                        Subject: [softrock40] Re: To match or not to match... BS170s in your RXTX


                        Sorry Taka,

                        I am too dumb to understand.

                        But finally I see. I need simple explanations without mathematics.
                        Q4 is configured to pass a constant current through R41. It does this by controlling Q5.
                        So Q5 source/gate voltage is set by Q4 so it will pass that constant current keeping Q4 base at ~0V7.
                        Q5 gate voltage will vary according to the temperature of Q5 (in thermal contact with Q7/8) and is sent to Q7/8 with D3 dropping
                        ~0V7 to compensate for Q4 base voltage.

                        Simple, but not as simple as me.

                        73 Alan G4ZFQ
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