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GM3SBC QRO Modifications

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  • Ed
    Hello All, I have uploaded the information on modifying the Softrock Ensemble RXTX to increase the TX RF Output Power. This information is detailed in the
    Message 1 of 15 , Mar 4, 2013
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      Hello All,

      I have uploaded the information on modifying the Softrock Ensemble RXTX to increase the TX RF Output Power. This information is detailed in the folder "GM3SBC QRO Modifications" within the files section.

      Thanks to the Moderator for freeing up some space.

      Best Regards to all and good DX !
      Ed GM3SBC
    • Chris Coe
      thanks, will take a look at it! -Chris
      Message 2 of 15 , Mar 4, 2013
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        thanks, will take a look at it!

        -Chris


        On Mon, Mar 4, 2013 at 1:49 PM, Ed <ed.murphy31@...> wrote:
         

        Hello All,

        I have uploaded the information on modifying the Softrock Ensemble RXTX to increase the TX RF Output Power. This information is detailed in the folder "GM3SBC QRO Modifications" within the files section.

        Thanks to the Moderator for freeing up some space.

        Best Regards to all and good DX !
        Ed GM3SBC


      • John Williams
        Ed, I did not see a BS170 matching procedure. I think you should add an appendix that describes how to match the 4 BS170 transistors, for easy reference. There
        Message 3 of 15 , Mar 4, 2013
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          Ed,

          I did not see a BS170 matching procedure. I think you should add an appendix that describes how to match the 4 BS170 transistors, for easy reference. There is a procedure external to your doc but over time links to external docs get stale.

          The reference to the ebay item will disappear in a few months. I think you need to list a well known manufacturer part number or farnell equiv.

          Otherwise an excellent writeup, anxious to start ordering parts!

          John - ke5ssh

          On 3/4/2013 12:49 PM, Ed wrote:
           

          Hello All,

          I have uploaded the information on modifying the Softrock Ensemble RXTX to increase the TX RF Output Power. This information is detailed in the folder "GM3SBC QRO Modifications" within the files section.

          Thanks to the Moderator for freeing up some space.

          Best Regards to all and good DX !
          Ed GM3SBC


          -- 
          
          John Williams
          
          KE5SSH - ham since 2007
          WQKA523 - GMRS for family use on the farm
          
        • warrenallgyer
          John Even with an unmodified RXTX I have not been able to quantify an operational benefit from matching BS170s. In the case of Ed s modifications I suspect
          Message 4 of 15 , Mar 4, 2013
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            John

            Even with an unmodified RXTX I have not been able to quantify an operational benefit from matching BS170s. In the case of Ed's modifications I suspect there is even less of one because he is using them well up on their current specification and the source resistors will tend to equalize the currents in each device at this level.

            Match if you like in order to distribute the static current but there is really not much value to it.

            Warren Allgyer - W8TOD

            --- In softrock40@yahoogroups.com, John Williams <KE5SSH@...> wrote:
            >
            > Ed,
            >
            > I did not see a BS170 matching procedure. I think you should add an
            > appendix that describes how to match the 4 BS170 transistors, for easy
            > reference. There is a procedure external to your doc but over time links
            > to external docs get stale.
            >
            > The reference to the ebay item will disappear in a few months. I think
            > you need to list a well known manufacturer part number or farnell equiv.
            >
            > Otherwise an excellent writeup, anxious to start ordering parts!
            >
            > John - ke5ssh
            >
            > On 3/4/2013 12:49 PM, Ed wrote:
            > >
            > > Hello All,
            > >
            > > I have uploaded the information on modifying the Softrock Ensemble
            > > RXTX to increase the TX RF Output Power. This information is detailed
            > > in the folder "GM3SBC QRO Modifications" within the files section.
            > >
            > > Thanks to the Moderator for freeing up some space.
            > >
            > > Best Regards to all and good DX !
            > > Ed GM3SBC
            > >
            > >
            >
            > --
            >
            > John Williams
            >
            > KE5SSH - ham since 2007
            > WQKA523 - GMRS for family use on the farm
            >
          • warrenallgyer
            In reading Ed s documents I note he does indeed call for four matched BS170. He has done extensive testing on this configuration and I would certainly defer to
            Message 5 of 15 , Mar 4, 2013
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              In reading Ed's documents I note he does indeed call for four matched BS170. He has done extensive testing on this configuration and I would certainly defer to him if he has found a benefit or necessity for matching.

              Warren Allgyer - W8TOD

              --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:
              >
              > John
              >
              > Even with an unmodified RXTX I have not been able to quantify an operational benefit from matching BS170s. In the case of Ed's modifications I suspect there is even less of one because he is using them well up on their current specification and the source resistors will tend to equalize the currents in each device at this level.
              >
              > Match if you like in order to distribute the static current but there is really not much value to it.
              >
              > Warren Allgyer - W8TOD
              >
              > --- In softrock40@yahoogroups.com, John Williams <KE5SSH@> wrote:
              > >
              > > Ed,
              > >
              > > I did not see a BS170 matching procedure. I think you should add an
              > > appendix that describes how to match the 4 BS170 transistors, for easy
              > > reference. There is a procedure external to your doc but over time links
              > > to external docs get stale.
              > >
              > > The reference to the ebay item will disappear in a few months. I think
              > > you need to list a well known manufacturer part number or farnell equiv.
              > >
              > > Otherwise an excellent writeup, anxious to start ordering parts!
              > >
              > > John - ke5ssh
              > >
              > > On 3/4/2013 12:49 PM, Ed wrote:
              > > >
              > > > Hello All,
              > > >
              > > > I have uploaded the information on modifying the Softrock Ensemble
              > > > RXTX to increase the TX RF Output Power. This information is detailed
              > > > in the folder "GM3SBC QRO Modifications" within the files section.
              > > >
              > > > Thanks to the Moderator for freeing up some space.
              > > >
              > > > Best Regards to all and good DX !
              > > > Ed GM3SBC
              > > >
              > > >
              > >
              > > --
              > >
              > > John Williams
              > >
              > > KE5SSH - ham since 2007
              > > WQKA523 - GMRS for family use on the farm
              > >
              >
            • Alan
              ... Subject: [softrock40] Re: GM3SBC QRO Modifications ... Warren, There have been a few cases where one of the BS170s has had a greatly different Gate
              Message 6 of 15 , Mar 4, 2013
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                ----- Original Message -----
                Subject: [softrock40] Re: GM3SBC QRO Modifications


                >
                > In reading Ed's documents I note he does indeed call for four matched BS170. He has done extensive testing on this configuration
                > and I would certainly defer to him if he has found a benefit or necessity for matching.
                >

                Warren,

                There have been a few cases where one of the BS170s has had a greatly different Gate Threshold Voltage. The specifications give a
                large possible range.
                Ed's mod makes that a bit more likely.

                I've not studied Ed's document thoroughly but see he's done very a good job.

                73 Alan G4ZFQ
              • warrenallgyer
                Hi Alan Yes I have seen a wide variance in Gate Threshold Voltage in the devices I have tested. I have not however been able to translate that into a
                Message 7 of 15 , Mar 5, 2013
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                  Hi Alan

                  Yes I have seen a wide variance in Gate Threshold Voltage in the devices I have tested. I have not however been able to translate that into a measurable impact on power output, inter-modulation, harmonic content, or stability. As I noted, I defer to Ed based on his extensive testing but I would be interested to know if anyone has observed any measurable operating impact from this variance.

                  Warren Allgyer - W8TOD

                  --
                  > Warren,
                  >
                  > There have been a few cases where one of the BS170s has had a greatly different Gate Threshold Voltage. The specifications give a
                  > large possible range.
                  > Ed's mod makes that a bit more likely.
                  >
                  > I've not studied Ed's document thoroughly but see he's done very a good job.
                  >
                  > 73 Alan G4ZFQ
                  >
                • Alan
                  ... Subject: [softrock40] Re: GM3SBC QRO Modifications ... I see Ed says 4 BS170s need to be matched but surely the one used as a bias source is also best
                  Message 8 of 15 , Mar 5, 2013
                  • 0 Attachment
                    ----- Original Message -----
                    Subject: [softrock40] Re: GM3SBC QRO Modifications


                    > Hi Alan
                    >
                    > Yes I have seen a wide variance in Gate Threshold Voltage in the devices I have tested. I have not however been able to translate
                    > that into a measurable impact on power output, inter-modulation, harmonic content, or stability. As I noted, I defer to Ed based
                    > on his extensive testing but I would be interested to know if anyone has observed any measurable operating impact from this
                    > variance.
                    >


                    I see Ed says 4 BS170s need to be matched but surely the one used as a bias source is also best matched?

                    The last instance of bad matching was due to a mis-matched Q5, causing the bias to be so low it cut off the PA devices. If all are
                    matched then the bias should be correct without requiring any adjustment.
                    And maybe no change to R41?

                    I cannot comment on the tolerable amount of mis-match, I'd guess a BS170 might be non-linear if it were cut off with no drive?

                    73 Alan G4ZFQ
                  • warrenallgyer
                    It remains a controversial subject.... I have not seen any evidence of the need but I am sure willing to be proven wrong. One possible weakness with Ed s
                    Message 9 of 15 , Mar 5, 2013
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                      It remains a controversial subject.... I have not seen any evidence of the need but I am sure willing to be proven wrong.

                      One possible weakness with Ed's design, and a possible reason for worrying more about the match, is the added two PAs on the bottom of the board are not thermally coupled to the bias BS170. This thermal coupling is largely responsible for the temperature stability of the original design. As the temperature of the assembly rises the bias is adjusted to compensate so they do not run away. The bottom two FETs are not coupled and potentially, I suppose, could run away without the bias FET being aware. The forced air cooling should prevent this but it does not have the benefit of the closed loop that the original design has.

                      As far as matching the bias FET.... I have posted my findings and opinions on that in the past and I have not had reason to change that position. To me it is "chicken soup"..... "it couldn't hurt".

                      Warren Allgyer - W8TOD

                      --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                      >
                      >
                      > ----- Original Message -----
                      > Subject: [softrock40] Re: GM3SBC QRO Modifications
                      >
                      >
                      > > Hi Alan
                      > >
                      > > Yes I have seen a wide variance in Gate Threshold Voltage in the devices I have tested. I have not however been able to translate
                      > > that into a measurable impact on power output, inter-modulation, harmonic content, or stability. As I noted, I defer to Ed based
                      > > on his extensive testing but I would be interested to know if anyone has observed any measurable operating impact from this
                      > > variance.
                      > >
                      >
                      >
                      > I see Ed says 4 BS170s need to be matched but surely the one used as a bias source is also best matched?
                      >
                      > The last instance of bad matching was due to a mis-matched Q5, causing the bias to be so low it cut off the PA devices. If all are
                      > matched then the bias should be correct without requiring any adjustment.
                      > And maybe no change to R41?
                      >
                      > I cannot comment on the tolerable amount of mis-match, I'd guess a BS170 might be non-linear if it were cut off with no drive?
                      >
                      > 73 Alan G4ZFQ
                      >
                    • Sid Boyce
                      Hi Warren, Looks like an alternative could be to mount the 4 FET s on a separate larger heatsink with 3 short leads from each pair to the board to address the
                      Message 10 of 15 , Mar 5, 2013
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                        Hi Warren,
                        Looks like an alternative could be to mount the 4 FET's on a separate larger heatsink with 3 short leads from each pair to the board to address the thermal issue? Ferrite beads on the gates?
                        73 ... Sid.

                        On 05/03/13 10:29, warrenallgyer wrote:
                         

                        It remains a controversial subject.... I have not seen any evidence of the need but I am sure willing to be proven wrong.

                        One possible weakness with Ed's design, and a possible reason for worrying more about the match, is the added two PAs on the bottom of the board are not thermally coupled to the bias BS170. This thermal coupling is largely responsible for the temperature stability of the original design. As the temperature of the assembly rises the bias is adjusted to compensate so they do not run away. The bottom two FETs are not coupled and potentially, I suppose, could run away without the bias FET being aware. The forced air cooling should prevent this but it does not have the benefit of the closed loop that the original design has.

                        As far as matching the bias FET.... I have posted my findings and opinions on that in the past and I have not had reason to change that position. To me it is "chicken soup"..... "it couldn't hurt".

                        Warren Allgyer - W8TOD

                        --- In softrock40@yahoogroups.com, "Alan" wrote:
                        >
                        >
                        > ----- Original Message -----
                        > Subject: [softrock40] Re: GM3SBC QRO Modifications
                        >
                        >
                        > > Hi Alan
                        > >
                        > > Yes I have seen a wide variance in Gate Threshold Voltage in the devices I have tested. I have not however been able to translate
                        > > that into a measurable impact on power output, inter-modulation, harmonic content, or stability. As I noted, I defer to Ed based
                        > > on his extensive testing but I would be interested to know if anyone has observed any measurable operating impact from this
                        > > variance.
                        > >
                        >
                        >
                        > I see Ed says 4 BS170s need to be matched but surely the one used as a bias source is also best matched?
                        >
                        > The last instance of bad matching was due to a mis-matched Q5, causing the bias to be so low it cut off the PA devices. If all are
                        > matched then the bias should be correct without requiring any adjustment.
                        > And maybe no change to R41?
                        >
                        > I cannot comment on the tolerable amount of mis-match, I'd guess a BS170 might be non-linear if it were cut off with no drive?
                        >
                        > 73 Alan G4ZFQ
                        >



                        -- 
                        Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                        Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                        Senior Staff Specialist, Cricket Coach
                        Microsoft Windows Free Zone - Linux used for all Computing Tasks
                        
                      • warrenallgyer
                        Sid It could be.... but Ed is clearly no amateur at this and it may not be a problem. I would be willing to try it. My 30/20/17 build puts out 2.6 watts in
                        Message 11 of 15 , Mar 5, 2013
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                          Sid

                          It could be.... but Ed is clearly no amateur at this and it may not be a problem. I would be willing to try it. My 30/20/17 build puts out 2.6 watts in its' stock condition. I tried some destructive testing on it I put it in full-power, key down operation for an hour and logged the power output and current consumption on one minute intervals. It was remarkably stable and did not run away for the entire hour. I am willing to bet that Ed's design may do the same so long as the fan is running. If, for some reason, the fan stops then all bets are off. It will rely on the match between the FETs being close enough that the thermal coupling between the top-of-board FETs and the bias FET can control the bias. I have no way of predicting if this will work other than trying it. And, assuming it does work... then the key would be within what matching parameters?

                          The original design is deceptively simple in appearance and very robust in operation. Ed's may be as well.... but it needs to be tested.

                          Warren Allgyer - W8TOD


                          --- In softrock40@yahoogroups.com, Sid Boyce <sboyce@...> wrote:
                          >
                          > Hi Warren,
                          > Looks like an alternative could be to mount the 4 FET's on a separate
                          > larger heatsink with 3 short leads from each pair to the board to
                          > address the thermal issue? Ferrite beads on the gates?
                          > 73 ... Sid.
                          >
                          > On 05/03/13 10:29, warrenallgyer wrote:
                          > >
                          > > It remains a controversial subject.... I have not seen any evidence of
                          > > the need but I am sure willing to be proven wrong.
                          > >
                          > > One possible weakness with Ed's design, and a possible reason for
                          > > worrying more about the match, is the added two PAs on the bottom of
                          > > the board are not thermally coupled to the bias BS170. This thermal
                          > > coupling is largely responsible for the temperature stability of the
                          > > original design. As the temperature of the assembly rises the bias is
                          > > adjusted to compensate so they do not run away. The bottom two FETs
                          > > are not coupled and potentially, I suppose, could run away without the
                          > > bias FET being aware. The forced air cooling should prevent this but
                          > > it does not have the benefit of the closed loop that the original
                          > > design has.
                          > >
                          > > As far as matching the bias FET.... I have posted my findings and
                          > > opinions on that in the past and I have not had reason to change that
                          > > position. To me it is "chicken soup"..... "it couldn't hurt".
                          > >
                          > > Warren Allgyer - W8TOD
                          > >
                          > > --- In softrock40@yahoogroups.com
                          > > <mailto:softrock40%40yahoogroups.com>, "Alan" wrote:
                          > > >
                          > > >
                          > > > ----- Original Message -----
                          > > > Subject: [softrock40] Re: GM3SBC QRO Modifications
                          > > >
                          > > >
                          > > > > Hi Alan
                          > > > >
                          > > > > Yes I have seen a wide variance in Gate Threshold Voltage in the
                          > > devices I have tested. I have not however been able to translate
                          > > > > that into a measurable impact on power output, inter-modulation,
                          > > harmonic content, or stability. As I noted, I defer to Ed based
                          > > > > on his extensive testing but I would be interested to know if
                          > > anyone has observed any measurable operating impact from this
                          > > > > variance.
                          > > > >
                          > > >
                          > > >
                          > > > I see Ed says 4 BS170s need to be matched but surely the one used as
                          > > a bias source is also best matched?
                          > > >
                          > > > The last instance of bad matching was due to a mis-matched Q5,
                          > > causing the bias to be so low it cut off the PA devices. If all are
                          > > > matched then the bias should be correct without requiring any
                          > > adjustment.
                          > > > And maybe no change to R41?
                          > > >
                          > > > I cannot comment on the tolerable amount of mis-match, I'd guess a
                          > > BS170 might be non-linear if it were cut off with no drive?
                          > > >
                          > > > 73 Alan G4ZFQ
                          > > >
                          > >
                          > >
                          >
                          >
                          > --
                          > Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                          > Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                          > Senior Staff Specialist, Cricket Coach
                          > Microsoft Windows Free Zone - Linux used for all Computing Tasks
                          >
                        • warrenallgyer
                          Sid Off my soapbox and responding directly to your suggestion: for the original design concept to work you need would need to tightly couple the 4 PAs and the
                          Message 12 of 15 , Mar 5, 2013
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                            Sid

                            Off my soapbox and responding directly to your suggestion: for the original design concept to work you need would need to tightly couple the 4 PAs and the bias FET. The key to the original circuit is the tight thermal coupling between the PAs and the bias FET. Once I realized this I took each of mine apart and applied a THIN layer of thermal grease on the backside of the heatsink. The bias FET must "feel the pain" of the two PAs in order to be stable under extended periods of high load.... like WSPR operations.

                            Under full load the negative feedback generated by the source resistance, together with the thermal adjustment of the bias, makes a very stable circuit. The two botom side PAs in the QRO design operate outside this thermal feedback loop and rely on air flow to keep them under control. This SHOULD work.... but they have no way to protest if it does not.

                            Warren Allgyer - W8TOD

                            --- In softrock40@yahoogroups.com, Sid Boyce <sboyce@...> wrote:
                            >
                            > Hi Warren,
                            > Looks like an alternative could be to mount the 4 FET's on a separate
                            > larger heatsink with 3 short leads from each pair to the board to
                            > address the thermal issue? Ferrite beads on the gates?
                            > 73 ... Sid.
                            >
                            > On 05/03/13 10:29, warrenallgyer wrote:
                            > >
                            > > It remains a controversial subject.... I have not seen any evidence of
                            > > the need but I am sure willing to be proven wrong.
                            > >
                            > > One possible weakness with Ed's design, and a possible reason for
                            > > worrying more about the match, is the added two PAs on the bottom of
                            > > the board are not thermally coupled to the bias BS170. This thermal
                            > > coupling is largely responsible for the temperature stability of the
                            > > original design. As the temperature of the assembly rises the bias is
                            > > adjusted to compensate so they do not run away. The bottom two FETs
                            > > are not coupled and potentially, I suppose, could run away without the
                            > > bias FET being aware. The forced air cooling should prevent this but
                            > > it does not have the benefit of the closed loop that the original
                            > > design has.
                            > >
                            > > As far as matching the bias FET.... I have posted my findings and
                            > > opinions on that in the past and I have not had reason to change that
                            > > position. To me it is "chicken soup"..... "it couldn't hurt".
                            > >
                            > > Warren Allgyer - W8TOD
                            > >
                            > > --- In softrock40@yahoogroups.com
                            > > <mailto:softrock40%40yahoogroups.com>, "Alan" wrote:
                            > > >
                            > > >
                            > > > ----- Original Message -----
                            > > > Subject: [softrock40] Re: GM3SBC QRO Modifications
                            > > >
                            > > >
                            > > > > Hi Alan
                            > > > >
                            > > > > Yes I have seen a wide variance in Gate Threshold Voltage in the
                            > > devices I have tested. I have not however been able to translate
                            > > > > that into a measurable impact on power output, inter-modulation,
                            > > harmonic content, or stability. As I noted, I defer to Ed based
                            > > > > on his extensive testing but I would be interested to know if
                            > > anyone has observed any measurable operating impact from this
                            > > > > variance.
                            > > > >
                            > > >
                            > > >
                            > > > I see Ed says 4 BS170s need to be matched but surely the one used as
                            > > a bias source is also best matched?
                            > > >
                            > > > The last instance of bad matching was due to a mis-matched Q5,
                            > > causing the bias to be so low it cut off the PA devices. If all are
                            > > > matched then the bias should be correct without requiring any
                            > > adjustment.
                            > > > And maybe no change to R41?
                            > > >
                            > > > I cannot comment on the tolerable amount of mis-match, I'd guess a
                            > > BS170 might be non-linear if it were cut off with no drive?
                            > > >
                            > > > 73 Alan G4ZFQ
                            > > >
                            > >
                            > >
                            >
                            >
                            > --
                            > Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                            > Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                            > Senior Staff Specialist, Cricket Coach
                            > Microsoft Windows Free Zone - Linux used for all Computing Tasks
                            >
                          • Sid Boyce
                            Thanks Warren, It s worth a try so I ll have a closer look at it. Out of 10 BS170 s in the pack from RS Components only 3 matched closely within 0.01V and the
                            Message 13 of 15 , Mar 5, 2013
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                              Thanks Warren,
                              It's worth a try so I'll have a closer look at it.

                              Out of 10 BS170's in the pack from RS Components only 3 matched closely within 0.01V and the 2 removed were in the same ball park.

                              The spread on the 10 were 3.13V - 3.18V. Whether the 3.18V ones would be OK to mix with 3.13V is the question.
                              73 ... Sid.
                               
                              On 05/03/13 15:10, warrenallgyer wrote:
                               

                              Sid

                              Off my soapbox and responding directly to your suggestion: for the original design concept to work you need would need to tightly couple the 4 PAs and the bias FET. The key to the original circuit is the tight thermal coupling between the PAs and the bias FET. Once I realized this I took each of mine apart and applied a THIN layer of thermal grease on the backside of the heatsink. The bias FET must "feel the pain" of the two PAs in order to be stable under extended periods of high load.... like WSPR operations.

                              Under full load the negative feedback generated by the source resistance, together with the thermal adjustment of the bias, makes a very stable circuit. The two botom side PAs in the QRO design operate outside this thermal feedback loop and rely on air flow to keep them under control. This SHOULD work.... but they have no way to protest if it does not.

                              Warren Allgyer - W8TOD

                              --- In softrock40@yahoogroups.com, Sid Boyce wrote:
                              >
                              > Hi Warren,
                              > Looks like an alternative could be to mount the 4 FET's on a separate
                              > larger heatsink with 3 short leads from each pair to the board to
                              > address the thermal issue? Ferrite beads on the gates?
                              > 73 ... Sid.
                              >
                              > On 05/03/13 10:29, warrenallgyer wrote:
                              > >
                              > > It remains a controversial subject.... I have not seen any evidence of
                              > > the need but I am sure willing to be proven wrong.
                              > >
                              > > One possible weakness with Ed's design, and a possible reason for
                              > > worrying more about the match, is the added two PAs on the bottom of
                              > > the board are not thermally coupled to the bias BS170. This thermal
                              > > coupling is largely responsible for the temperature stability of the
                              > > original design. As the temperature of the assembly rises the bias is
                              > > adjusted to compensate so they do not run away. The bottom two FETs
                              > > are not coupled and potentially, I suppose, could run away without the
                              > > bias FET being aware. The forced air cooling should prevent this but
                              > > it does not have the benefit of the closed loop that the original
                              > > design has.
                              > >
                              > > As far as matching the bias FET.... I have posted my findings and
                              > > opinions on that in the past and I have not had reason to change that
                              > > position. To me it is "chicken soup"..... "it couldn't hurt".
                              > >
                              > > Warren Allgyer - W8TOD
                              > >
                              > > --- In softrock40@yahoogroups.com
                              > > , "Alan" wrote:
                              > > >
                              > > >
                              > > > ----- Original Message -----
                              > > > Subject: [softrock40] Re: GM3SBC QRO Modifications
                              > > >
                              > > >
                              > > > > Hi Alan
                              > > > >
                              > > > > Yes I have seen a wide variance in Gate Threshold Voltage in the
                              > > devices I have tested. I have not however been able to translate
                              > > > > that into a measurable impact on power output, inter-modulation,
                              > > harmonic content, or stability. As I noted, I defer to Ed based
                              > > > > on his extensive testing but I would be interested to know if
                              > > anyone has observed any measurable operating impact from this
                              > > > > variance.
                              > > > >
                              > > >
                              > > >
                              > > > I see Ed says 4 BS170s need to be matched but surely the one used as
                              > > a bias source is also best matched?
                              > > >
                              > > > The last instance of bad matching was due to a mis-matched Q5,
                              > > causing the bias to be so low it cut off the PA devices. If all are
                              > > > matched then the bias should be correct without requiring any
                              > > adjustment.
                              > > > And maybe no change to R41?
                              > > >
                              > > > I cannot comment on the tolerable amount of mis-match, I'd guess a
                              > > BS170 might be non-linear if it were cut off with no drive?
                              > > >
                              > > > 73 Alan G4ZFQ
                              > > >
                              > >
                              > >
                              >
                              >



                              -- 
                              Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                              Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                              Senior Staff Specialist, Cricket Coach
                              Microsoft Windows Free Zone - Linux used for all Computing Tasks
                              
                            • John Williams
                              Ed, What is the motivation of changing the 2n2222 to a BS170? Does it offer an independent improvement or is it in conjunction with the piggybacking of the
                              Message 14 of 15 , Mar 13, 2013
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                                Ed,

                                What is the motivation of changing the 2n2222 to a BS170? Does it offer
                                an independent improvement or is it in conjunction with the piggybacking
                                of the main BS170 quad circuit? Looking to understand the design theory...

                                John - ke5ssh
                                On 3/4/2013 12:49 PM, Ed wrote:
                                > modifying the Softrock Ensemble RXTX to increase the TX RF Output Power

                                --

                                John Williams

                                KE5SSH - ham since 2007
                                WQKA523 - GMRS for family use on the farm
                              • Adam Jacobs
                                Sorry to resurrect a very old thread, but I m interested in this as well. I noticed that the amplifier design theory is not described very well at all (if at
                                Message 15 of 15 , May 8, 2013
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                                  Sorry to resurrect a very old thread, but I'm interested in this as well. I noticed that the amplifier design theory is not described very well at all (if at all) in the uploaded word document and I don't see any discussion in this email thread either. Is Ed still on the list to give a design theory explanation?

                                  Thanks,
                                   -73 Adam W7QI


                                  On Wed, Mar 13, 2013 at 7:59 AM, John Williams <KE5SSH@...> wrote:
                                   

                                  Ed,

                                  What is the motivation of changing the 2n2222 to a BS170? Does it offer
                                  an independent improvement or is it in conjunction with the piggybacking
                                  of the main BS170 quad circuit? Looking to understand the design theory...

                                  John - ke5ssh
                                  On 3/4/2013 12:49 PM, Ed wrote:
                                  > modifying the Softrock Ensemble RXTX to increase the TX RF Output Power

                                  --

                                  John Williams

                                  KE5SSH - ham since 2007
                                  WQKA523 - GMRS for family use on the farm


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