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Re: Fw: Re: Fw: Re: Fw: Re: [softrock40] FST switches

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  • KD5NWA
    I just received some 74ac74 s from Mouser they have a 134MHz minimum clocking frequency and typical 200MHz, so you don t need to go power crazy to get up
    Message 1 of 29 , Mar 30, 2006
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      I just received some 74ac74's from Mouser they have a 134MHz minimum clocking frequency and typical 200MHz, so you don't need to go power crazy to get up there. Cost $.34 in small qty.


      At 06:27 AM 3/30/2006, you wrote:
      Bob and the group.

      The biggest problem with jitter seems to occur when we use RC based
      phase shift components to obtain operation at higher frequencies.
      This is no surprise, none of us would use an RC network for a VFO,
      even at VLF. Well, these QSD beasts seem to be very susceptible to
      losses from jittter and perhaps a step backwards to a counter based
      QSD is a better answer.

      "FET physics" is severely limited for all but the lowest frequency
      useable-again, this is no surprise. The cmos based logic analog
      switches we use today draw almost no current, are VERY cheap, easy to
      design with and have good isolation and relatively low dynamic on
      resistance. But, saying they 'suck' for the upper part of the HF
      spectrum QSD based projects is a fair assessment.

      The answer of course is phemt based switches and ECL control
      logic-and to use counters rather than RC based phase shift networks
      to minimize jitter losses. Neither of these families are inexpensive
      and circuits built with them would probably draw several hundred
      milliamps of supply current. Higher speed means more power is
      needed....and both ECL and PHEMT draw very substantial amounts of
      quiescent power because they have to be biased in order to avoid the
      sluggish transitions associated with cut off and saturation.

      Before jumping to PHEMT and ECL however, it might be appropriate to
      evaluate 74F and other faster digital solutions with discrete PIN
      switching diodes. Sure, it wouldn't be as compact as an FST3125 cmos
      switch, but I think it might allow counters to be used well into the
      upper HF regions, or possibly at 6 meters.

      My 20 year old Kenwood TS711A 2 meter multimode uses a pin diode
      switch to isolate a 25 watt transmitter from it's own gasfet front
      end-and it hears well. So, these types of switches are viable at VHF.
      I know they are fast enough to allow 2 meter rigs to be used as
      active radar, several hams have done radar on 2 meters using PIN switches.

      A (Fairchild) 74H74 goes to 125 MHz and draws 16 ma. A (TI) 74S74
      goes to 110 MHz and draws 15 ma. Both of these chips enable full QSD
      using the divider method for frequencies up to 10 meters.

      The point I'm trying to make is that there are 'middle of the road'
      options available for high performance QSD based receivers without
      resorting to RC based analog phase shift methods that leave a lot to
      be desired with respect to jitter losses.

      Regards,

      Art




      >In addition, as Cecil Bayona and others have pointed out,  we are never
      >going to get either the QSD or the Moda/H-Mode to work at greater than
      >(say) 100 Mhz reliably until we get away from "FET physics".  You can
      >just count on 5-6 ns of up and down time no matter how good the rest of
      >the circuit is.


      --
      No virus found in this outgoing message.
      Checked by AVG Anti-Virus.
      Version: 7.1.385 / Virus Database: 268.3.2/293 - Release Date: 3/26/2006




       
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      Cecil Bayona
      KD5NWA
      www.qrpradio.com

      I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

    • KD5NWA
      That is one of the big advantages of using FET s over diodes, they are either on, or they are off, they don t operate in the middle( normally). They make much
      Message 2 of 29 , Mar 30, 2006
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        That is one of the big advantages of using FET's over diodes, they are either on, or they are off, they don't operate in the middle( normally). They make much more efficient mixers, but as we been discussing there are some problems. One thing to note is that if you look in the Internet there are folks that have used older FET switches past the 6M band. So the FST family with improved on/off timing and on resistance should too. But I keep sensing a large reluctance to have a pre-amp in front of the QSD and that will limit your success in the higher bands no matter how low the loss of the mixer is.

        On a let's be kinder and gentler note.

        The other day we had a member from Europe give some of his experiences, and he got jumped on pretty hard. Yes you can prove through mathematics that 2 Quadrature 50% mixer is not as efficient as a 4 Quadrature 25% mixer, but guess what? He has had his radio working just fine before many of us started involved in QSD radios. And he has gotten his mixers to work as high as 70MHz using older switches so maybe he knows something that we can benefit from.

        Enough ranting, I'm going back to my tree house, ugh, me Tarzan, you not Jane.


        At 07:11 AM 3/30/2006, you wrote:
        Art,

        PIN diodes cause intermod as well.  An RF signal can cause the PIN diode
        to turn on more, so you get less loss at high signal levels especially
        with low bias currents.   In other words they are non-linear.

        Bill  WB5TCO

        KY1K wrote:

        > Bob and the group.
        >
        > The biggest problem with jitter seems to occur when we use RC based
        > phase shift components to obtain operation at higher frequencies.
        > This is no surprise, none of us would use an RC network for a VFO,
        > even at VLF. Well, these QSD beasts seem to be very susceptible to
        > losses from jittter and perhaps a step backwards to a counter based
        > QSD is a better answer.
        >
        > "FET physics" is severely limited for all but the lowest frequency
        > useable-again, this is no surprise. The cmos based logic analog
        > switches we use today draw almost no current, are VERY cheap, easy to
        > design with and have good isolation and relatively low dynamic on
        > resistance. But, saying they 'suck' for the upper part of the HF
        > spectrum QSD based projects is a fair assessment.
        >
        > The answer of course is phemt based switches and ECL control
        > logic-and to use counters rather than RC based phase shift networks
        > to minimize jitter losses. Neither of these families are inexpensive
        > and circuits built with them would probably draw several hundred
        > milliamps of supply current. Higher speed means more power is
        > needed....and both ECL and PHEMT draw very substantial amounts of
        > quiescent power because they have to be biased in order to avoid the
        > sluggish transitions associated with cut off and saturation.
        >
        > Before jumping to PHEMT and ECL however, it might be appropriate to
        > evaluate 74F and other faster digital solutions with discrete PIN
        > switching diodes. Sure, it wouldn't be as compact as an FST3125 cmos
        > switch, but I think it might allow counters to be used well into the
        > upper HF regions, or possibly at 6 meters.
        >
        > My 20 year old Kenwood TS711A 2 meter multimode uses a pin diode
        > switch to isolate a 25 watt transmitter from it's own gasfet front
        > end-and it hears well. So, these types of switches are viable at VHF.
        > I know they are fast enough to allow 2 meter rigs to be used as
        > active radar, several hams have done radar on 2 meters using PIN switches.
        >
        > A (Fairchild) 74H74 goes to 125 MHz and draws 16 ma. A (TI) 74S74
        > goes to 110 MHz and draws 15 ma. Both of these chips enable full QSD
        > using the divider method for frequencies up to 10 meters.
        >
        > The point I'm trying to make is that there are 'middle of the road'
        > options available for high performance QSD based receivers without
        > resorting to RC based analog phase shift methods that leave a lot to
        > be desired with respect to jitter losses.
        >
        > Regards,
        >
        > Art
        >
        >
        >
        >
        > >In addition, as Cecil Bayona and others have pointed out,  we are never
        > >going to get either the QSD or the Moda/H-Mode to work at greater than
        > >(say) 100 Mhz reliably until we get away from "FET physics".  You can
        > >just count on 5-6 ns of up and down time no matter how good the rest of
        > >the circuit is.
        >
        >
        > --
        > No virus found in this outgoing message.
        > Checked by AVG Anti-Virus.
        > Version: 7.1.385 / Virus Database: 268.3.2/293 - Release Date: 3/26/2006
        >
        >
        >
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        Cecil Bayona
        KD5NWA
        www.qrpradio.com

        I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

      • KD5NWA
        Using high power has it s own set of problems, since the clocks are in the band we are trying to receive, too much power makes it easier to pick up the LO on
        Message 3 of 29 , Mar 30, 2006
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          Using high power has it's own set of problems, since the clocks are in the band we are trying to receive, too much power makes it easier to pick up the LO on the input stages. That is not so good either.

          At 07:12 AM 3/30/2006, you wrote:
          Hi all, Just a quick question. Why are we worried about drawing current?

          If  half an amp is the price for a performance front end for our SDR,
          then so be it. Half an amp at 5Volts ins 2.5 Watts. I dread to thing
          what current my FT-920 draws on receive!.

          Enjoying the technical debate. It beats the hell out of some of the dumb
          comments I see on some other sites.

          73 Clive G0PPO

          KY1K wrote:
          > Bob and the group.
          >
          > The biggest problem with jitter seems to occur when we use RC based
          > phase shift components to obtain operation at higher frequencies.
          > This is no surprise, none of us would use an RC network for a VFO,
          > even at VLF. Well, these QSD beasts seem to be very susceptible to
          > losses from jittter and perhaps a step backwards to a counter based
          > QSD is a better answer.
          >
          > "FET physics" is severely limited for all but the lowest frequency
          > useable-again, this is no surprise. The cmos based logic analog
          > switches we use today draw almost no current, are VERY cheap, easy to
          > design with and have good isolation and relatively low dynamic on
          > resistance. But, saying they 'suck' for the upper part of the HF
          > spectrum QSD based projects is a fair assessment.
          >
          > The answer of course is phemt based switches and ECL control
          > logic-and to use counters rather than RC based phase shift networks
          > to minimize jitter losses. Neither of these families are inexpensive
          > and circuits built with them would probably draw several hundred
          > milliamps of supply current. Higher speed means more power is
          > needed....and both ECL and PHEMT draw very substantial amounts of
          > quiescent power because they have to be biased in order to avoid the
          > sluggish transitions associated with cut off and saturation.
          >
          > Before jumping to PHEMT and ECL however, it might be appropriate to
          > evaluate 74F and other faster digital solutions with discrete PIN
          > switching diodes. Sure, it wouldn't be as compact as an FST3125 cmos
          > switch, but I think it might allow counters to be used well into the
          > upper HF regions, or possibly at 6 meters.
          >
          > My 20 year old Kenwood TS711A 2 meter multimode uses a pin diode
          > switch to isolate a 25 watt transmitter from it's own gasfet front
          > end-and it hears well. So, these types of switches are viable at VHF.
          > I know they are fast enough to allow 2 meter rigs to be used as
          > active radar, several hams have done radar on 2 meters using PIN switches.
          >
          > A (Fairchild) 74H74 goes to 125 MHz and draws 16 ma. A (TI) 74S74
          > goes to 110 MHz and draws 15 ma. Both of these chips enable full QSD
          > using the divider method for frequencies up to 10 meters.
          >
          > The point I'm trying to make is that there are 'middle of the road'
          > options available for high performance QSD based receivers without
          > resorting to RC based analog phase shift methods that leave a lot to
          > be desired with respect to jitter losses.
          >
          > Regards,
          >
          > Art
          >
          >
          >
          >
          >  
          >> In addition, as Cecil Bayona and others have pointed out,  we are never
          >> going to get either the QSD or the Moda/H-Mode to work at greater than
          >> (say) 100 Mhz reliably until we get away from "FET physics".  You can
          >> just count on 5-6 ns of up and down time no matter how good the rest of
          >> the circuit is.
          >>    
          >
          >
          >  



           
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          Cecil Bayona
          KD5NWA
          www.qrpradio.com

          I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ...

        • n7ve
          The power consumed by the 74AC74 parts vary with the clocking frequency. The parts have both a static power consumption and a dynamic power consumption often
          Message 4 of 29 , Mar 30, 2006
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            The power consumed by the 74AC74 parts vary with the clocking
            frequency. The parts have both a static power consumption and a
            dynamic power consumption often specified as Cd. I like the AC family
            because it has a lot of drive capability, and works very well for
            driving a couple of BS170s (a higher power version of a 2n7000) to a
            couple of watts.

            However, the AC family has a rather high Cd rating. I have not
            examined the most recent logic families, but the AHC parts are very
            fast and have a much lower Cd rating, thus using less power.

            In my NC2030, I used a 1/4 wave C/L/C phase delay section. This
            produces much less phase noise than a less expensive R/C delay
            primarily because the resulting sine wave has a very steep slope as it
            goes through it zero crossing compared to the more gradual decay of an
            R/C section. This does help improve phase noise.

            In addition, I use a logic gate to square up the sine wave rather than
            a comparator. I think this is both faster and cheaper than using a
            comparator, but may require more power. A large resistor such as 100K
            is connected from output to input of one of these gates to bias the
            input into the linear range, and the input is AC coupled. Not all
            logic families will square a sine wave to a 50-50 duty cycle output.
            I have seen that a 74AC00 will not, but a 74AHC00 will. I used this on
            both the ScQRPions frequency counter and the NC2030. A caution is
            that this approach oscillates with no input, but in this case, we
            always have LO input.

            The combination of the logic gate squaring and the C/L/C phase delay
            section allowed me to achieve 145 db of blocking dynamic range on the
            NC2030, which would not be possible if phase noise were an issue.

            - Dan, N7VE

            --- In softrock40@yahoogroups.com, KD5NWA <KD5NWA@...> wrote:
            >
            > I just received some 74ac74's from Mouser they have a 134MHz minimum
            > clocking frequency and typical 200MHz, so you don't need to go power
            > crazy to get up there. Cost $.34 in small qty.
            >
            >
            > At 06:27 AM 3/30/2006, you wrote:
            > >Bob and the group.
            > >
            > >The biggest problem with jitter seems to occur when we use RC based
            > >phase shift components to obtain operation at higher frequencies.
            > >This is no surprise, none of us would use an RC network for a VFO,
            > >even at VLF. Well, these QSD beasts seem to be very susceptible to
            > >losses from jittter and perhaps a step backwards to a counter based
            > >QSD is a better answer.
            > >
            > >"FET physics" is severely limited for all but the lowest frequency
            > >useable-again, this is no surprise. The cmos based logic analog
            > >switches we use today draw almost no current, are VERY cheap, easy to
            > >design with and have good isolation and relatively low dynamic on
            > >resistance. But, saying they 'suck' for the upper part of the HF
            > >spectrum QSD based projects is a fair assessment.
            > >
            > >The answer of course is phemt based switches and ECL control
            > >logic-and to use counters rather than RC based phase shift networks
            > >to minimize jitter losses. Neither of these families are inexpensive
            > >and circuits built with them would probably draw several hundred
            > >milliamps of supply current. Higher speed means more power is
            > >needed....and both ECL and PHEMT draw very substantial amounts of
            > >quiescent power because they have to be biased in order to avoid the
            > >sluggish transitions associated with cut off and saturation.
            > >
            > >Before jumping to PHEMT and ECL however, it might be appropriate to
            > >evaluate 74F and other faster digital solutions with discrete PIN
            > >switching diodes. Sure, it wouldn't be as compact as an FST3125 cmos
            > >switch, but I think it might allow counters to be used well into the
            > >upper HF regions, or possibly at 6 meters.
            > >
            > >My 20 year old Kenwood TS711A 2 meter multimode uses a pin diode
            > >switch to isolate a 25 watt transmitter from it's own gasfet front
            > >end-and it hears well. So, these types of switches are viable at VHF.
            > >I know they are fast enough to allow 2 meter rigs to be used as
            > >active radar, several hams have done radar on 2 meters using PIN
            switches.
            > >
            > >A (Fairchild) 74H74 goes to 125 MHz and draws 16 ma. A (TI) 74S74
            > >goes to 110 MHz and draws 15 ma. Both of these chips enable full QSD
            > >using the divider method for frequencies up to 10 meters.
            > >
            > >The point I'm trying to make is that there are 'middle of the road'
            > >options available for high performance QSD based receivers without
            > >resorting to RC based analog phase shift methods that leave a lot to
            > >be desired with respect to jitter losses.
            > >
            > >Regards,
            > >
            > >Art
            > >
            > >
            > >
            > >
            > > >In addition, as Cecil Bayona and others have pointed out, we are
            never
            > > >going to get either the QSD or the Moda/H-Mode to work at greater
            than
            > > >(say) 100 Mhz reliably until we get away from "FET physics". You can
            > > >just count on 5-6 ns of up and down time no matter how good the
            rest of
            > > >the circuit is.
            > >
            > >
            > >--
            > >No virus found in this outgoing message.
            > >Checked by AVG Anti-Virus.
            > >Version: 7.1.385 / Virus Database: 268.3.2/293 - Release Date:
            3/26/2006
            > >
            > >
            > >
            > >
            > >
            > >Yahoo! Groups Links
            > >
            > >
            > >
            > >
            >
            >
            > Cecil Bayona
            > KD5NWA
            > www.qrpradio.com
            >
            > I fail to see why doing the same thing over and over and getting the
            > same results every time is insanity: I've almost proved it isn't;
            > only a few more tests now and I'm sure results will differ this time ...
            >
          • FRANCIS CARCIA
            years ago I worked on radar with tapped LC delay lines. They were always a tapped inductor with a cap to ground at the tap. I ll have to dig through the cob
            Message 5 of 29 , Mar 30, 2006
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              years ago I worked on radar with tapped LC delay lines. They were always a tapped inductor with a cap to ground at the tap. I'll have to dig through the cob webs detween my ears to remember the ns/section and LLC ratios based on operating Z. Ah the old TEK 545B scope was so much better than the 545A.  When set up properly the output was a nice square wave.
              AC parts are great but need a good ground under them and proper bypassing to really work correctly.  fc  

              n7ve <dan.Tayloe@...> wrote:
              The power consumed by the 74AC74 parts vary with the clocking
              frequency.  The parts have both a static power consumption and a
              dynamic power consumption often specified as Cd.  I like the AC family
              because it has a lot of drive capability, and works very well for
              driving a couple of BS170s (a higher power version of a 2n7000) to a
              couple of watts.

              However, the AC family has a rather high Cd rating.  I have not
              examined the most recent logic families, but the AHC parts are very
              fast and have a much lower Cd rating, thus using less power.

              In my NC2030, I used a 1/4 wave C/L/C phase delay section.  This
              produces much less phase noise than a less expensive R/C delay
              primarily because the resulting sine wave has a very steep slope as it
              goes through it zero crossing compared to the more gradual decay of an
              R/C section.  This does help improve phase noise.

              In addition, I use a logic gate to square up the sine wave rather than
              a comparator.  I think this is both faster and cheaper than using a
              comparator, but may require more power.  A large resistor such as 100K
              is connected from output to input of one of these gates to bias the
              input into the linear range, and the input is AC coupled.  Not all
              logic families will square a sine wave to a 50-50 duty cycle output.
              I have seen that a 74AC00 will not, but a 74AHC00 will. I used this on
              both the ScQRPions frequency counter and the NC2030.  A caution is
              that this approach oscillates with no input, but in this case, we
              always have LO input.

              The combination of the logic gate squaring and the C/L/C phase delay
              section allowed me to achieve 145 db of blocking dynamic range on the
              NC2030, which would not be possible if phase noise were an issue.

              - Dan, N7VE

              --- In softrock40@yahoogroups.com, KD5NWA <KD5NWA@...> wrote:
              >
              > I just received some 74ac74's from Mouser they have a 134MHz minimum
              > clocking frequency and typical 200MHz, so you don't need to go power
              > crazy to get up there. Cost $.34 in small qty.
              >
              >
              > At 06:27 AM 3/30/2006, you wrote:
              > >Bob and the group.
              > >
              > >The biggest problem with jitter seems to occur when we use RC based
              > >phase shift components to obtain operation at higher frequencies.
              > >This is no surprise, none of us would use an RC network for a VFO,
              > >even at VLF. Well, these QSD beasts seem to be very susceptible to
              > >losses from jittter and perhaps a step backwards to a counter based
              > >QSD is a better answer.
              > >
              > >"FET physics" is severely limited for all but the lowest frequency
              > >useable-again, this is no surprise. The cmos based logic analog
              > >switches we use today draw almost no current, are VERY cheap, easy to
              > >design with and have good isolation and relatively low dynamic on
              > >resistance. But, saying they 'suck' for the upper part of the HF
              > >spectrum QSD based projects is a fair assessment.
              > >
              > >The answer of course is phemt based switches and ECL control
              > >logic-and to use counters rather than RC based phase shift networks
              > >to minimize jitter losses. Neither of these families are inexpensive
              > >and circuits built with them would probably draw several hundred
              > >milliamps of supply current. Higher speed means more power is
              > >needed....and both ECL and PHEMT draw very substantial amounts of
              > >quiescent power because they have to be biased in order to avoid the
              > >sluggish transitions associated with cut off and saturation.
              > >
              > >Before jumping to PHEMT and ECL however, it might be appropriate to
              > >evaluate 74F and other faster digital solutions with discrete PIN
              > >switching diodes. Sure, it wouldn't be as compact as an FST3125 cmos
              > >switch, but I think it might allow counters to be used well into the
              > >upper HF regions, or possibly at 6 meters.
              > >
              > >My 20 year old Kenwood TS711A 2 meter multimode uses a pin diode
              > >switch to isolate a 25 watt transmitter from it's own gasfet front
              > >end-and it hears well. So, these types of switches are viable at VHF.
              > >I know they are fast enough to allow 2 meter rigs to be used as
              > >active radar, several hams have done radar on 2 meters using PIN
              switches.
              > >
              > >A (Fairchild) 74H74 goes to 125 MHz and draws 16 ma. A (TI) 74S74
              > >goes to 110 MHz and draws 15 ma. Both of these chips enable full QSD
              > >using the divider method for frequencies up to 10 meters.
              > >
              > >The point I'm trying to make is that there are 'middle of the road'
              > >options available for high performance QSD based receivers without
              > >resorting to RC based analog phase shift methods that leave a lot to
              > >be desired with respect to jitter losses.
              > >
              > >Regards,
              > >
              > >Art
              > >
              > >
              > >
              > >
              > > >In addition, as Cecil Bayona and others have pointed out,  we are
              never
              > > >going to get either the QSD or the Moda/H-Mode to work at greater
              than
              > > >(say) 100 Mhz reliably until we get away from "FET physics".  You can
              > > >just count on 5-6 ns of up and down time no matter how good the
              rest of
              > > >the circuit is.
              > >
              > >
              > >--
              > >No virus found in this outgoing message.
              > >Checked by AVG Anti-Virus.
              > >Version: 7.1.385 / Virus Database: 268.3.2/293 - Release Date:
              3/26/2006
              > >
              > >
              > >
              > >
              > >
              > >Yahoo! Groups Links
              > >
              > >
              > >
              > >
              >
              >
              > Cecil Bayona
              > KD5NWA
              > www.qrpradio.com
              >
              > I fail to see why doing the same thing over and over and getting the
              > same results every time is insanity: I've almost proved it isn't;
              > only a few more tests now and I'm sure results will differ this time ...
              >





            • mdgolfbum
              Phil Covington Any news on Phil Harmon s work? 73 jim ab3cv ... wrote: [...]
              Message 6 of 29 , May 8, 2006
              • 0 Attachment
                Phil Covington

                Any news on Phil Harmon's work?

                73

                jim ab3cv

                --- In softrock40@yahoogroups.com, "Phil Covington" <p.covington@...>
                wrote:
                [...]
                > Luckily, Phil Harmon is working on a non-QSD based design that uses
                > the same bus switches, but does not have the degradation of SNR with
                > frequency that the QSD does.
                >
                > 73 de Phil N8VB
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