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Re: FM pulse counting receiver

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  • Peter Blakey
    I believe that the venerable 30-year old TDA7000 IC is a complete implementation of a pulse counting FM receiver. This IC was very popular as a simple way to
    Message 1 of 20 , Apr 1, 2013
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      I believe that the venerable 30-year old TDA7000 IC is a complete implementation of a pulse counting FM receiver. This IC was very popular as a simple way to obtain very high quality (but mono) reception of FM signals. The IC is still readily available, and kits based on the TDA7000 can still be purchased, e.g. on ebay.


      Peter, kk7wm


      [Non-text portions of this message have been removed]
    • Dayle Edwards
      Peter, yes, I had forgotten that one. It also uses a clever frequency locking arrangement too , the AFC voltage is largely unfiltered, so that its fed back to
      Message 2 of 20 , Apr 1, 2013
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        Peter, yes, I had forgotten that one. It also uses a clever frequency
        locking arrangement too , the AFC voltage is largely unfiltered, so
        that its fed back to the oscillator to aid the correct signal, and
        cancels the image, although both carriers are received equally. This
        also allows a high bandwidth signal to fit through a narrow IF. ..the
        IF frequency used by memory is very low, like 50 Kcs or even less. I
        think these are now only available in SM packages making them a tad
        difficult to use..





        On Tue, Apr 2, 2013, at 01:42 AM, Peter Blakey wrote:



        I believe that the venerable 30-year old TDA7000 IC is a complete
        implementation of a pulse counting FM receiver. This IC was very
        popular as a simple way to obtain very high quality (but mono)
        reception of FM signals. The IC is still readily available, and kits
        based on the TDA7000 can still be purchased, e.g. on ebay.

        Peter, kk7wm

        [Non-text portions of this message have been removed]





        --
        Dayle Edwards
        dayleedwards@...

        References

        1. http://groups.yahoo.com/group/regenrx/post;_ylc=X3oDMTJyanVkamliBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARtc2dJZAMxNzI0MgRzZWMDZnRyBHNsawNycGx5BHN0aW1lAzEzNjQ4MjAxNTk-?act=reply&messageNum=17242
        2. mailto:pblakey@...?subject=Re%3A%20FM%20pulse%20counting%20receiver
        3. mailto:regenrx@yahoogroups.com?subject=Re%3A%20FM%20pulse%20counting%20receiver
        4. http://groups.yahoo.com/group/regenrx/post;_ylc=X3oDMTJmZzdzcmRkBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDZnRyBHNsawNudHBjBHN0aW1lAzEzNjQ4MjAxNTk-
        5. http://groups.yahoo.com/group/regenrx/message/17236;_ylc=X3oDMTM3azUyZ2dzBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARtc2dJZAMxNzI0MgRzZWMDZnRyBHNsawN2dHBjBHN0aW1lAzEzNjQ4MjAxNTkEdHBjSWQDMTcyMzY-
        6. http://groups.yahoo.com/group/regenrx/members;_ylc=X3oDMTJnYzQ5aTdyBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDdnRsBHNsawN2bWJycwRzdGltZQMxMzY0ODIwMTU5?o=6
        7. http://groups.yahoo.com/group/regenrx;_ylc=X3oDMTJmNWcybGg3BF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDdnRsBHNsawN2Z2hwBHN0aW1lAzEzNjQ4MjAxNTk-
        8. http://groups.yahoo.com/;_ylc=X3oDMTJlMDJkdmpmBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDZnRyBHNsawNnZnAEc3RpbWUDMTM2NDgyMDE1OQ--
        9. mailto:regenrx-traditional@yahoogroups.com?subject=Change%20Delivery%20Format:%20Traditional
        10. mailto:regenrx-digest@yahoogroups.com?subject=Email%20Delivery:%20Digest
        11. mailto:regenrx-unsubscribe@yahoogroups.com?subject=Unsubscribe
        12. http://docs.yahoo.com/info/terms/
        13. mailto:ygroupsnotifications@yahoogroups.com?subject=Feedback%20on%20the%20redesigned%20individual%20mail%20v1


        [Non-text portions of this message have been removed]
      • Dave McGuire
        ... Eh...Different, not necessarily difficult. It requires different tools and a different skill set. I started with through-hole (like most everyone I
        Message 3 of 20 , Apr 1, 2013
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          On 04/01/2013 08:55 AM, Dayle Edwards wrote:
          > Peter, yes, I had forgotten that one. It also uses a clever frequency
          > locking arrangement too , the AFC voltage is largely unfiltered, so
          > that its fed back to the oscillator to aid the correct signal, and
          > cancels the image, although both carriers are received equally. This
          > also allows a high bandwidth signal to fit through a narrow IF. ..the
          > IF frequency used by memory is very low, like 50 Kcs or even less. I
          > think these are now only available in SM packages making them a tad
          > difficult to use..

          Eh...Different, not necessarily difficult. It requires different tools and
          a different skill set. I started with through-hole (like most everyone I
          suppose) but now I can't stand it, much preferring the speed and ease of
          surface mount. (plus, every through-hole package on a board dramatically
          increases assembly cost, a concern for commercial designs)

          -Dave

          --
          Dave McGuire, AK4HZ
          New Kensington, PA
        • aurel.zlatko
          ... Yes TDA7000 use very much similar method with +/- 70kHz osc frequency. But in first place i want to know how circuit work with transistors not with chip,
          Message 4 of 20 , Apr 1, 2013
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            --- In regenrx@yahoogroups.com, Dave McGuire <Mcguire@...> wrote:
            >
            > On 04/01/2013 08:55 AM, Dayle Edwards wrote:
            > > Peter, yes, I had forgotten that one. It also uses a clever frequency
            > > locking arrangement too , the AFC voltage is largely unfiltered, so
            > > that its fed back to the oscillator to aid the correct signal, and
            > > cancels the image, although both carriers are received equally. This
            > > also allows a high bandwidth signal to fit through a narrow IF. ..the
            > > IF frequency used by memory is very low, like 50 Kcs or even less. I
            > > think these are now only available in SM packages making them a tad
            > > difficult to use..
            >
            > Eh...Different, not necessarily difficult. It requires different tools and
            > a different skill set. I started with through-hole (like most everyone I
            > suppose) but now I can't stand it, much preferring the speed and ease of
            > surface mount. (plus, every through-hole package on a board dramatically
            > increases assembly cost, a concern for commercial designs)
            >
            > -Dave
            >
            > --
            > Dave McGuire, AK4HZ
            > New Kensington, PA
            >

            Yes TDA7000 use very much similar method with +/- 70kHz osc frequency.
            But in first place i want to know how circuit work with transistors not with chip, clones of tda7000 works very fine with clear sound.
            I have fond something with schmidt trigers and i must look at it better...
          • Dave McGuire
            ... That s good thinking, there. ... Schmitt triggers for FM demodulation?? Sounds like an interesting trick! -Dave -- Dave McGuire, AK4HZ New Kensington, PA
            Message 5 of 20 , Apr 1, 2013
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              On 04/01/2013 10:21 AM, aurel.zlatko wrote:
              >>> Peter, yes, I had forgotten that one. It also uses a clever frequency
              >>> locking arrangement too , the AFC voltage is largely unfiltered, so
              >>> that its fed back to the oscillator to aid the correct signal, and
              >>> cancels the image, although both carriers are received equally. This
              >>> also allows a high bandwidth signal to fit through a narrow IF. ..the
              >>> IF frequency used by memory is very low, like 50 Kcs or even less. I
              >>> think these are now only available in SM packages making them a tad
              >>> difficult to use..
              >>
              >> Eh...Different, not necessarily difficult. It requires different tools and
              >> a different skill set. I started with through-hole (like most everyone I
              >> suppose) but now I can't stand it, much preferring the speed and ease of
              >> surface mount. (plus, every through-hole package on a board dramatically
              >> increases assembly cost, a concern for commercial designs)
              >
              > Yes TDA7000 use very much similar method with +/- 70kHz osc frequency.
              > But in first place i want to know how circuit work with transistors not with chip, clones of tda7000 works very fine with clear sound.

              That's good thinking, there.

              > I have fond something with schmidt trigers and i must look at it better...

              Schmitt triggers for FM demodulation?? Sounds like an interesting trick!

              -Dave

              --
              Dave McGuire, AK4HZ
              New Kensington, PA
            • Bill Cromwell
              ... Hi Dave, That bit about assembly is true enough for manufacturers. But most (all?) of the list members are hobbyists. It is often pointed out, to the
              Message 6 of 20 , Apr 1, 2013
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                On Mon, 2013-04-01 at 10:10 -0400, Dave McGuire wrote:

                >
                >
                > Eh...Different, not necessarily difficult. It requires different tools
                > and
                > a different skill set. I started with through-hole (like most everyone
                > I
                > suppose) but now I can't stand it, much preferring the speed and ease
                > of
                > surface mount. (plus, every through-hole package on a board
                > dramatically
                > increases assembly cost, a concern for commercial designs)
                >
                > -Dave
                >
                > --
                > Dave McGuire, AK4HZ
                > New Kensington, PA


                Hi Dave,

                That bit about assembly is true enough for manufacturers. But most
                (all?) of the list members are hobbyists. It is often pointed out, to
                the discouragement od many, that "they need a factory to make
                those" (whatever the "those" may be). We only need a factory and only
                concern ourselves about how long it takes to make things in mass
                production. Anybody can make one of almost anything without a factory no
                big hurry if it's a hobby.

                73,

                Bill KU8H
              • Dave McGuire
                ... Very true, and while most of my designs are volume-produced in a factory, I do all the prototyping (usually only a dozen units or so) by hand. Hand
                Message 7 of 20 , Apr 1, 2013
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                  On 04/01/2013 11:16 AM, Bill Cromwell wrote:
                  >> Eh...Different, not necessarily difficult. It requires different tools
                  >> and
                  >> a different skill set. I started with through-hole (like most everyone
                  >> I
                  >> suppose) but now I can't stand it, much preferring the speed and ease
                  >> of
                  >> surface mount. (plus, every through-hole package on a board
                  >> dramatically
                  >> increases assembly cost, a concern for commercial designs)
                  >
                  > That bit about assembly is true enough for manufacturers. But most
                  > (all?) of the list members are hobbyists. It is often pointed out, to
                  > the discouragement od many, that "they need a factory to make
                  > those" (whatever the "those" may be). We only need a factory and only
                  > concern ourselves about how long it takes to make things in mass
                  > production. Anybody can make one of almost anything without a factory no
                  > big hurry if it's a hobby.

                  Very true, and while most of my designs are volume-produced in a factory, I
                  do all the prototyping (usually only a dozen units or so) by hand. Hand
                  construction of surface-mount stuff is what I was talking about, appropriate
                  for the context of this list. Lots of people shy away from it because they
                  "tried it" with their through-hole soldering tools, experience, and muscle
                  memory. Everything is different for SM.

                  -Dave

                  --
                  Dave McGuire, AK4HZ
                  New Kensington, PA
                • Bill Cromwell
                  Hi Dave, I m approaching the surface mount stuff here. I ve used really small through hole soldering irons with those parts before - successfully but I have
                  Message 8 of 20 , Apr 1, 2013
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                    Hi Dave,

                    I'm approaching the surface mount stuff here. I've used really small
                    "through hole" soldering irons with those parts before - successfully
                    but I have to find something better to do very much of it. I'm not sure
                    I could successfully do multi-terminal parts without destroying
                    sumpthin'. I'll see what I can do about that.

                    73,

                    Bill KU8H
                  • Dave McGuire
                    ... I can make some equipment recommendations when the time comes. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
                    Message 9 of 20 , Apr 1, 2013
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                      On 04/01/2013 02:32 PM, Bill Cromwell wrote:
                      > I'm approaching the surface mount stuff here. I've used really small
                      > "through hole" soldering irons with those parts before - successfully
                      > but I have to find something better to do very much of it. I'm not sure
                      > I could successfully do multi-terminal parts without destroying
                      > sumpthin'. I'll see what I can do about that.

                      I can make some equipment recommendations when the time comes.

                      -Dave

                      --
                      Dave McGuire, AK4HZ
                      New Kensington, PA
                    • Dayle Edwards
                      I well remember my first SM repair. I put on TWO pair of reading glasses, a big magnifier and took a look at the faulty chip. Great I thought, its now a little
                      Message 10 of 20 , Apr 1, 2013
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                        I well remember my first SM repair. I put on TWO pair of reading
                        glasses, a big magnifier and took a look at the faulty chip. Great I
                        thought, its now a little larger than a normal 16 pin DIL....I can deal
                        to that. Came to get the iron tip into view, it was 6 inches long and 2
                        inches wide, the .5 mill solder looked like fencing wire. Managed the
                        repair.......just! A similar thing when ICs first arrived in the late
                        60s. Here they were commonly used by local manufacturers with the left
                        over or even current miniature valve type components, making me wonder
                        what the point of miniaturisation actually was. I can see now that the
                        human race is expected to evolve in Darwinian fashion, getting smaller
                        fingers, better eyes, and to operate ever smaller smart and clever
                        devices as our under used brains turn to nano dust.

                        You tube has some excellent SM soldering tutorials, one uses a normal
                        iron, but with a hollowed tip. ALL 150 odd pins are plastered with
                        solder, then cunningly redone with this tip that pulls out the excess..
                        a perfect job done in seconds!!



                        On Tue, Apr 2, 2013, at 07:39 AM, Dave McGuire wrote:



                        On 04/01/2013 02:32 PM, Bill Cromwell wrote:
                        > I'm approaching the surface mount stuff here. I've used really small
                        > "through hole" soldering irons with those parts before - successfully
                        > but I have to find something better to do very much of it. I'm not
                        sure
                        > I could successfully do multi-terminal parts without destroying
                        > sumpthin'. I'll see what I can do about that.

                        I can make some equipment recommendations when the time comes.

                        -Dave

                        --
                        Dave McGuire, AK4HZ
                        New Kensington, PA




                        --
                        Dayle Edwards
                        dayleedwards@...

                        References

                        1. http://groups.yahoo.com/group/regenrx/post;_ylc=X3oDMTJycmE5b21qBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARtc2dJZAMxNzI1MARzZWMDZnRyBHNsawNycGx5BHN0aW1lAzEzNjQ4NDE1NzM-?act=reply&messageNum=17250
                        2. mailto:mcguire@...?subject=Re%3A%20%5Bregenrx%5D%20Re%3A%20FM%20pulse%20counting%20receiver
                        3. mailto:regenrx@yahoogroups.com?subject=Re%3A%20%5Bregenrx%5D%20Re%3A%20FM%20pulse%20counting%20receiver
                        4. http://groups.yahoo.com/group/regenrx/post;_ylc=X3oDMTJmdmQwazV2BF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDZnRyBHNsawNudHBjBHN0aW1lAzEzNjQ4NDE1NzM-
                        5. http://groups.yahoo.com/group/regenrx/message/17236;_ylc=X3oDMTM3M2NmNDVqBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARtc2dJZAMxNzI1MARzZWMDZnRyBHNsawN2dHBjBHN0aW1lAzEzNjQ4NDE1NzMEdHBjSWQDMTcyMzY-
                        6. http://groups.yahoo.com/group/regenrx/members;_ylc=X3oDMTJnN2hyZmRsBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDdnRsBHNsawN2bWJycwRzdGltZQMxMzY0ODQxNTcz?o=6
                        7. http://groups.yahoo.com/group/regenrx;_ylc=X3oDMTJmMDNpbW9xBF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDdnRsBHNsawN2Z2hwBHN0aW1lAzEzNjQ4NDE1NzM-
                        8. http://groups.yahoo.com/;_ylc=X3oDMTJlNnFwbzU5BF9TAzk3MzU5NzE0BGdycElkAzEzOTk2OTA3BGdycHNwSWQDMTcwNTA2MzEwOARzZWMDZnRyBHNsawNnZnAEc3RpbWUDMTM2NDg0MTU3Mw--
                        9. mailto:regenrx-traditional@yahoogroups.com?subject=Change%20Delivery%20Format:%20Traditional
                        10. mailto:regenrx-digest@yahoogroups.com?subject=Email%20Delivery:%20Digest
                        11. mailto:regenrx-unsubscribe@yahoogroups.com?subject=Unsubscribe
                        12. http://docs.yahoo.com/info/terms/
                        13. mailto:ygroupsnotifications@yahoogroups.com?subject=Feedback%20on%20the%20redesigned%20individual%20mail%20v1


                        [Non-text portions of this message have been removed]
                      • Dave McGuire
                        ... Yep. ... That technique is called dragging . That s what I usually use for small volumes. Drowning the area with a good-quality liquid flux helps a lot.
                        Message 11 of 20 , Apr 1, 2013
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                          On 04/01/2013 07:28 PM, Dayle Edwards wrote:
                          > I well remember my first SM repair. I put on TWO pair of reading
                          > glasses, a big magnifier and took a look at the faulty chip. Great I
                          > thought, its now a little larger than a normal 16 pin DIL....I can deal
                          > to that. Came to get the iron tip into view, it was 6 inches long and 2
                          > inches wide, the .5 mill solder looked like fencing wire. Managed the
                          > repair.......just! A similar thing when ICs first arrived in the late
                          > 60s. Here they were commonly used by local manufacturers with the left
                          > over or even current miniature valve type components, making me wonder
                          > what the point of miniaturisation actually was. I can see now that the
                          > human race is expected to evolve in Darwinian fashion, getting smaller
                          > fingers, better eyes, and to operate ever smaller smart and clever
                          > devices as our under used brains turn to nano dust.

                          Yep.

                          > You tube has some excellent SM soldering tutorials, one uses a normal
                          > iron, but with a hollowed tip. ALL 150 odd pins are plastered with
                          > solder, then cunningly redone with this tip that pulls out the excess..
                          > a perfect job done in seconds!!

                          That technique is called "dragging". That's what I usually use for small
                          volumes. Drowning the area with a good-quality liquid flux helps a lot.
                          Surface tension works in your favor, and it's very easy to clean it up. If
                          I'm having a good day, by using this technique I can do an entire 144-pin QFP
                          with 0.5mm pin spacing with no wick cleanup afterwards...soldering 144 pins
                          in less than a minute. I adore surface mount. :)

                          -Dave

                          --
                          Dave McGuire, AK4HZ
                          New Kensington, PA
                        • aurelsetwich
                          ... Please guys...do we can back to topic and not discuse about soldering ???? Just friendly tip! Anyone maybe have something new about FM pulse counting
                          Message 12 of 20 , Apr 1, 2013
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                            --- In regenrx@yahoogroups.com, Dave McGuire <Mcguire@...> wrote:
                            >
                            > On 04/01/2013 07:28 PM, Dayle Edwards wrote:
                            > > I well remember my first SM repair. I put on TWO pair of reading
                            > > glasses, a big magnifier and took a look at the faulty chip. Great I
                            > > thought, its now a little larger than a normal 16 pin DIL....I can deal
                            > > to that. Came to get the iron tip into view, it was 6 inches long and 2
                            > > inches wide, the .5 mill solder looked like fencing wire. Managed the
                            > > repair.......just! A similar thing when ICs first arrived in the late
                            > > 60s. Here they were commonly used by local manufacturers with the left
                            > > over or even current miniature valve type components, making me wonder
                            > > what the point of miniaturisation actually was. I can see now that the
                            > > human race is expected to evolve in Darwinian fashion, getting smaller
                            > > fingers, better eyes, and to operate ever smaller smart and clever
                            > > devices as our under used brains turn to nano dust.
                            >
                            > Yep.
                            >
                            > > You tube has some excellent SM soldering tutorials, one uses a normal
                            > > iron, but with a hollowed tip. ALL 150 odd pins are plastered with
                            > > solder, then cunningly redone with this tip that pulls out the excess..
                            > > a perfect job done in seconds!!
                            >
                            > That technique is called "dragging". That's what I usually use for small
                            > volumes. Drowning the area with a good-quality liquid flux helps a lot.
                            > Surface tension works in your favor, and it's very easy to clean it up. If
                            > I'm having a good day, by using this technique I can do an entire 144-pin QFP
                            > with 0.5mm pin spacing with no wick cleanup afterwards...soldering 144 pins
                            > in less than a minute. I adore surface mount. :)
                            >
                            > -Dave
                            >
                            > --
                            > Dave McGuire, AK4HZ
                            > New Kensington, PA
                            >

                            Please guys...do we can back to topic and not discuse about
                            soldering ????
                            Just friendly tip!
                            Anyone maybe have something new about FM pulse counting receiver????
                          • Electrojim
                            My firm uses a pulse-counting FM detector in our FM Mod-Monitor for broadcasters. The 10.7MHz first IF is taken down to a 700kHz second IF, then 4000-series
                            Message 13 of 20 , Apr 2, 2013
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                              My firm uses a pulse-counting FM detector in our FM Mod-Monitor for broadcasters. The 10.7MHz first IF is taken down to a 700kHz second IF, then 4000-series CMOS chips and discrete parts do the rest. It's a push-pull design that pretty well removes the 700kHz from the recovered FM baseband signal, which is flat out to 100kHz, and distortion and stereo separation are excellent. Download the manual here:
                              http://www.inovonicsbroadcast.com/wp-content/uploads/catablog/downloads/531Manual.pdf
                              for schematics and circuit descriptions. Parts-intensive and not simple, but sure does work well.


                              --- In regenrx@yahoogroups.com, Dave McGuire <Mcguire@...> wrote:
                              >
                              > On 04/01/2013 10:21 AM, aurel.zlatko wrote:
                              > >>> Peter, yes, I had forgotten that one. It also uses a clever frequency
                              > >>> locking arrangement too , the AFC voltage is largely unfiltered, so
                              > >>> that its fed back to the oscillator to aid the correct signal, and
                              > >>> cancels the image, although both carriers are received equally. This
                              > >>> also allows a high bandwidth signal to fit through a narrow IF. ..the
                              > >>> IF frequency used by memory is very low, like 50 Kcs or even less. I
                              > >>> think these are now only available in SM packages making them a tad
                              > >>> difficult to use..
                              > >>
                              > >> Eh...Different, not necessarily difficult. It requires different tools and
                              > >> a different skill set. I started with through-hole (like most everyone I
                              > >> suppose) but now I can't stand it, much preferring the speed and ease of
                              > >> surface mount. (plus, every through-hole package on a board dramatically
                              > >> increases assembly cost, a concern for commercial designs)
                              > >
                              > > Yes TDA7000 use very much similar method with +/- 70kHz osc frequency.
                              > > But in first place i want to know how circuit work with transistors not with chip, clones of tda7000 works very fine with clear sound.
                              >
                              > That's good thinking, there.
                              >
                              > > I have fond something with schmidt trigers and i must look at it better...
                              >
                              > Schmitt triggers for FM demodulation?? Sounds like an interesting trick!
                              >
                              > -Dave
                              >
                              > --
                              > Dave McGuire, AK4HZ
                              > New Kensington, PA
                              >
                            • Dave McGuire
                              ... Wow, that s pretty impressive. And VERY impressive documentation! That level of in-depth circuit description is pretty rare these days. I am particularly
                              Message 14 of 20 , Apr 2, 2013
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                                On 04/02/2013 10:40 AM, Electrojim wrote:
                                > My firm uses a pulse-counting FM detector in our FM Mod-Monitor for broadcasters. The 10.7MHz first IF is taken down to a 700kHz second IF, then 4000-series CMOS chips and discrete parts do the rest. It's a push-pull design that pretty well removes the 700kHz from the recovered FM baseband signal, which is flat out to 100kHz, and distortion and stereo separation are excellent. Download the manual here:
                                > http://www.inovonicsbroadcast.com/wp-content/uploads/catablog/downloads/531Manual.pdf
                                > for schematics and circuit descriptions. Parts-intensive and not simple, but sure does work well.

                                Wow, that's pretty impressive.

                                And VERY impressive documentation! That level of in-depth circuit
                                description is pretty rare these days.

                                I am particularly intrigued by the fancy filter design on page 48.

                                -Dave

                                --
                                Dave McGuire, AK4HZ
                                New Kensington, PA
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