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Re: SV: [softrock40] Re: Fst3251 max frequency ?

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  • Flemming Nielsen
    Hi Cecil.   Thanks for your reply!   I do not think that noise will be the problem because it only changes the filter and switch between tx and rx, not qsd
    Message 1 of 6 , Apr 1, 2010
    • 0 Attachment
      Hi Cecil.
       
      Thanks for your reply!
       
      I do not think that noise will be the problem because it only changes the filter and switch between tx and rx, not qsd circuits. . It may be possible at higher frequencies it will have a gain problem but fortunately UHFSDR has a high gain in the RX side. I was concerned about it should have an opamp after the bandpass filter but it is not necessary.
       
      2m is probably worth a try ! .
       
      I am a little worry about gain in ( on hf ) , because my antenna is only a 10 m long wire with a ( homemade made ) 1:9 balun to
      ground. Strong signals is not a problem here .With better antennas it maybe will be best with a 10 or 20db attenuator.
       
      Mobo PCBs are very kombatibelt (if you're a little creative) I have also used v 3.6 with 3. transverters and a separate si570
      pcb . There you must modify  transformer and  component to 28mhz between dbm and the stage to the rx side , and antenna direkt to the transverter pcb.
       
      This only works on rx side !
      It might be fun to mount the automatic band pass filter from kb9yig in the last of the 4 slots.
      Maybe there will be a gain loss!  2*2 fst32xx .
      I think that I will have a lot of fun with the new mobo!
       
      We could use a mobo pcb designed for the v 9 only for rx.

      73 vy OZ5AGk / Flemming




      --- Den tors 1/4/10 skrev k5nwa <k5nwa@...>:

      Fra: k5nwa <k5nwa@...>
      Emne: Re: SV: [softrock40] Re: Fst3251 max frequency ?
      Til: softrock40@yahoogroups.com
      Dato: torsdag 1. april 2010 17.49

       
      The typical on time is 2.5 ns, I talked to one of the engineers that worked on that chip and he stated it's more like 1ns to get 90% conduction.

      The main problem with the device is that the turn on time is faster than the turn off time. This makes it have increasing noise with frequency.

      I did some experiments some time back where I had a special clock generator (4 quadrature clocks) that created clocks that had a few ns of space between I and Q  so that a switch could turn off completely before the next turned on and it made a big difference in noise at 10M and 6M.

      At 10:35 AM 4/1/2010, you wrote:


      Hi sv1eia
       
      Datasheet is a god thing but it,s  not always that the data stays with in the specified field.
       
      Eks. si570 cmos , says 160mhz but I have one there works very well on 250mhz .
      I am  making some mods on the mobo 4,3 for the uhfsdr from wb6dhw . ( when it arrivals ) transformers ,Pa,ect .  The uhfsdr is finnish and works very well.
       
      One linie to the mobo and one for 2m , but I hope that I can have 4m-6m runnning on the mobo . Maybee also 2m.
       
      It,s good with some info from some one , there  have been playing with it in praxis !
       
      Best regards Flemming / oz5agk


      --- Den tors 1/4/10 skrev sv1eia <sv1eia@yahoo. com>:

      Fra: sv1eia <sv1eia@yahoo. com>
      Emne: [softrock40] Re: Fst3251 max frequency ?
      Til: softrock40@yahoogro ups.com
      Dato: torsdag 1. april 2010 16.39

       
      Hi Flemming,

      You can check the datasheet, it specifies something between 6.0ns to 6.5ns on the switching so it seems that it can go around 180MHz (/4 = 45MHz VFO)

      Why do you ask others for something that you can find easily on your own?

      73,
      SV1EIA

      --- In softrock40@yahoogro ups.com, "daekt1" <daekt1@...> wrote:
      >
      > Hi !
      >
      > Are there any members of the group who know the max frequency of
      > fst3251 ?
      >
      >
      > 73 vy OZ5AGK / Flemming
      >


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      Cecil
      K5NWA
      www.softrockradio. org  www.qrpradio. com

      "Blessed are the cracked, for they shall let in the light."

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    • Michael
      What was the verdict on the max freq passed through? Did it make it to 600mhz-the or higher? Mike KC7NOA
      Message 2 of 6 , Mar 5 12:07 PM
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        What was the verdict on the max freq passed through? Did it make it to 600mhz-the or higher?

        Mike KC7NOA

        --- In softrock40@yahoogroups.com, Flemming Nielsen <daekt1@...> wrote:
        >
        > Hi Cecil.
        >  
        > Thanks for your reply!
        >  
        > I do not think that noise will be the problem because it only changes the filter and switch between tx and rx, not qsd circuits. . It may be possible at higher frequencies it will have a gain problem but fortunately UHFSDR has a high gain in the RX side. I was concerned about it should have an opamp after the bandpass filter but it is not necessary.
        >  
        > 2m is probably worth a try ! .
        >  
        > I am a little worry about gain in ( on hf ) , because my antenna is only a 10 m long wire with a ( homemade made ) 1:9 balun to
        > ground. Strong signals is not a problem here .With better antennas it maybe will be best with a 10 or 20db attenuator.
        >  
        > Mobo PCBs are very kombatibelt (if you're a little creative) I have also used v 3.6 with 3. transverters and a separate si570
        > pcb . There you must modify  transformer and  component to 28mhz between dbm and the stage to the rx side , and antenna direkt to the transverter pcb.
        >  
        > This only works on rx side !
        >
        > It might be fun to mount the automatic band pass filter from kb9yig in the last of the 4 slots.
        > Maybe there will be a gain loss!  2*2 fst32xx .
        >
        > I think that I will have a lot of fun with the new mobo!
        >  
        > We could use a mobo pcb designed for the v 9 only for rx.
        >
        > 73 vy OZ5AGk / Flemming
        >
        >
        >
        >
        > --- Den tors 1/4/10 skrev k5nwa <k5nwa@...>:
        >
        >
        > Fra: k5nwa <k5nwa@...>
        > Emne: Re: SV: [softrock40] Re: Fst3251 max frequency ?
        > Til: softrock40@yahoogroups.com
        > Dato: torsdag 1. april 2010 17.49
        >
        >
        >  
        >
        >
        >
        > The typical on time is 2.5 ns, I talked to one of the engineers that worked on that chip and he stated it's more like 1ns to get 90% conduction.
        >
        > The main problem with the device is that the turn on time is faster than the turn off time. This makes it have increasing noise with frequency.
        >
        > I did some experiments some time back where I had a special clock generator (4 quadrature clocks) that created clocks that had a few ns of space between I and Q  so that a switch could turn off completely before the next turned on and it made a big difference in noise at 10M and 6M.
        >
        > At 10:35 AM 4/1/2010, you wrote:
        >
        >
        >
        > Hi sv1eia
        >  
        > Datasheet is a god thing but it,s  not always that the data stays with in the specified field.
        >  
        > Eks. si570 cmos , says 160mhz but I have one there works very well on 250mhz .
        > I am  making some mods on the mobo 4,3 for the uhfsdr from wb6dhw . ( when it arrivals ) transformers ,Pa,ect .  The uhfsdr is finnish and works very well.
        >  
        > One linie to the mobo and one for 2m , but I hope that I can have 4m-6m runnning on the mobo . Maybee also 2m.
        >  
        > It,s good with some info from some one , there  have been playing with it in praxis !
        >  
        > Best regards Flemming / oz5agk
        >
        >
        > --- Den tors 1/4/10 skrev sv1eia <sv1eia@yahoo. com>:
        >
        >
        >
        > Fra: sv1eia <sv1eia@yahoo. com>
        >
        > Emne: [softrock40] Re: Fst3251 max frequency ?
        >
        > Til: softrock40@yahoogro ups.com
        >
        > Dato: torsdag 1. april 2010 16.39
        >
        >
        >  
        >
        > Hi Flemming,
        >
        >
        > You can check the datasheet, it specifies something between 6.0ns to 6.5ns on the switching so it seems that it can go around 180MHz (/4 = 45MHz VFO)
        >
        >
        > Why do you ask others for something that you can find easily on your own?
        >
        >
        > 73,
        >
        > SV1EIA
        >
        >
        > --- In softrock40@yahoogro ups.com, "daekt1" <daekt1@> wrote:
        >
        > >
        >
        > > Hi !
        >
        > >
        >
        > > Are there any members of the group who know the max frequency of
        >
        > > fst3251 ?
        >
        > >
        >
        > >
        >
        > > 73 vy OZ5AGK / Flemming
        >
        > >
        >
        >
        > ____________ _________ _________ _________ _________ __
        > Bruger du Yahoo!?
        > Er du træt af spam? Yahoo!Mail har den bedste spambeskyttelse, der findes
        > http://dk.mail yahoo.com
        >
        >
        >
        > Cecil
        > K5NWA
        > www.softrockradio. org  www.qrpradio. com
        >
        > "Blessed are the cracked, for they shall let in the light."
        >
        >
        >
        >
        >
        >
        > __________________________________________________
        > Bruger du Yahoo!?
        > Er du træt af spam? Yahoo!Mail har den bedste spambeskyttelse, der findes
        > http://dk.mail.yahoo.com
        >
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