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Re: [softrock40] Re: Linear Amp for QRP

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  • Lawrence Galea
    Fastest fuse on three legs Regards Lawrence ________________________________ Da: John Rabson A: softrock40@yahoogroups.com Inviato:
    Message 1 of 12 , Jun 2, 2012
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      Fastest fuse on three legs
      Regards
      Lawrence


      Da: John Rabson <john.rabson@...>
      A: softrock40@yahoogroups.com
      Inviato: Sabato 2 Giugno 2012 7:36
      Oggetto: Re: [softrock40] Re: Linear Amp for QRP

       
      On 1 Jun 2012, at 22:45CEST, Dave B wrote:

       

      Should be OK, clean/linear, and rugged (VSWR tollerant) at 50W or so, so
      long as you have good (FAST!) over current protection on the DC supply.

      And a power semicondictor is the fastest fuse known to man.

      John F5VLF



    • Jasmine Strong
      Not quite as fast as a laserdiode. Spikes as short as 2 ns can destroy a laserdiode. -J.
      Message 2 of 12 , Jun 2, 2012
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        Not quite as fast as a laserdiode. Spikes as short as 2 ns can destroy a laserdiode.

        -J.

        On 2 Jun 2012, at 12:59, Lawrence Galea wrote:

         

        Fastest fuse on three legs
        Regards
        Lawrence


        Da: John Rabson <john.rabson@...>
        A: softrock40@yahoogroups.com
        Inviato: Sabato 2 Giugno 2012 7:36
        Oggetto: Re: [softrock40] Re: Linear Amp for QRP

         
        On 1 Jun 2012, at 22:45CEST, Dave B wrote:

         

        Should be OK, clean/linear, and rugged (VSWR tollerant) at 50W or so, so
        long as you have good (FAST!) over current protection on the DC supply.

        And a power semicondictor is the fastest fuse known to man.

        John F5VLF





      • Dave B
        Oh yes!... How fast a power semi self destructs, is directly proportional to the cost x diffulty of it s replacement! Protection is everything! The use of
        Message 3 of 12 , Jun 3, 2012
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          Oh yes!...

          How fast a power semi' self destructs, is directly proportional to the
          cost x diffulty of it's replacement!

          Protection is everything! The use of active current limiting/foldback
          on the DC supply, is just as esential as active monitoring of both
          forward and reflected power levels, with any needed warnings, trips, or
          automatic drive level reduction under extreme load VSWR contitions.

          It's especially a problem when such amps are driving very low impedances
          (as the devices "see" them) the currents developed rise scarily fast.
          That coupled with transmission line effects due to standing waves can
          result in an instant device failure, if something goes "open circuit"
          somewhere downstream. (1/4 wave transformer effects...)

          A solid state RF PA, is in essance a controled voltage generator, with
          (relatively) uncontroled currents. (DC and RF!) Yes, the device
          controls current itself, but under normal conditions that current is also
          a function of the DC input voltage and output load impedance, as "seen"
          by the PA stage. If the dynamic working point of the device stray's out
          of the "Safe Operating Area" into Secondary Breakdown teretory, the rest
          as they say is history. And very fast too.

          A Tube amp by comparison, is a controled current source, that can
          withstand (in the most part) high voltages under fault conditions, so can
          be less problematical, though not always in narrowband configurations,
          and especially not at VHF, where its often other parts that fail first,
          not the tube itself. (Cap's flashing over etc.)

          Tubes tend not to fail "Instantly" for the most part (if the amp is
          correctly designed for the tube in use) but give enough warning to the
          user that something is wrong by way of real time meetering in sight of
          the operator. But of course, the operator needs to know how to
          interperate those readings, and keep an eye on them. There are some
          commercial tube amps that automate all that, some better than others.

          I have yet to see even a commercial solid state PA, that has DC input
          current meetering, though often Fwd and Refl power metering is included.

          73

          Dave G0WBX.
        • Alex
          ... I have a ensemble rxtx and I built a kit amp from http://www.golddredgervideo.com/kc0wox/wa2ebyamp/ Take a look at this amp 40w out with 1w in. It works
          Message 4 of 12 , Jun 3, 2012
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            --- In softrock40@yahoogroups.com, Bruce Tanner <bet110@...> wrote:
            >
            > The thought did cross my mind!
            >
            > On 5/31/2012 3:40 PM, MIKE DURKIN wrote:
            > >
            > > With a pair of 2sc2879's .... 120w each .... id guess more are sold to
            > > CB'rs than hams ...
            > >
            > > -----Original Message-----
            > >
            > > From: Mike WA8BXN
            > > Sent: 31 May 2012 16:34:31 GMT
            > > To: softrock40@yahoogroups.com
            > > Subject: Re: [softrock40] Linear Amp for QRP
            > >
            > > It looks like it lacks bandpass filters.
            > >
            > >
            > >
            > >
            > > -------Original Message-------
            > >
            > > From: k2bet1
            > > Date: 5/31/2012 11:32:24 AM
            > > To: softrock40@yahoogroups.com <mailto:softrock40%40yahoogroups.com>
            > > Subject: [softrock40] Linear Amp for QRP
            > >
            > >
            > > I wonder if anyone has looked more closely at this amp? No affiliation
            > > just
            > > wondering what you think. Looks a bit like the Tokyo Hy-Power HL-45B.
            > >
            > > http://www.ebay
            > > com/itm/SSB-CW-HF-LINEAR-AMP-180W-QRP-SDR-817s-/150805937814?_trksid=p4340
            > > m1374&_trkparms=algo%3DUPI
            > > GIROS%26its%3DI%252BC%252BS%26itu%3DUCI%252BUCC%26otn%3D13%26pmod%3D290718831
            > > 68%26ps%3D63%26clkid%3D8806789656698524272
            > >
            > > bet
            > >
            > >
            > >
            > >
            > >
            > >
            > > __________ Information from ESET Smart Security, version of virus
            > > signature database 7185 (20120531) __________
            > >
            > > The message was checked by ESET Smart Security.
            > >
            > > http://www.eset.com
            >Hi Bruce,

            I have a ensemble rxtx and I built a kit amp from http://www.golddredgervideo.com/kc0wox/wa2ebyamp/
            Take a look at this amp 40w out with 1w in. It works absolutely beautiful with the softrock ensemble rxtx. I get about 45w out and everyone tells me how great it sound.
            You can easily get all parts from mouser or digikey.
            There is a link on the arrl article for this amp on where to get the printed circuit boards. Not hard to build at all.

            Good luck W6ACT
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