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Re: [softrock40] finals from a tube rig?

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  • Pete Ferrand
    Hi Justin: This should work just fine, I ve been a using the amplifier portion of a Swan SS-200 transceiver to amplify the 1 watt output of my Flex-Radio
    Message 1 of 9 , Feb 22, 2010
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      Hi Justin:

      This should work just fine, I've been a using the amplifier portion of a Swan SS-200 transceiver to amplify the 1 watt output of my Flex-Radio SDR-1000 for almost two years now.

      Now the SS-200 is a solid state rig but the principle's the same. The thing is, you probably don't have enough power to easily drive the finals directly, so you feed the SoftRock output to the input of the driver tube. In the case of my SS-200 I'm feeding the pre pre driver transistor with small resistive pad that provides a 50 ohm load back to the SDR-1000. You'll have to figure out what works here given the load impedances. It's a simple and non-detructive mod.

      You'll have to rework the t/r switching of course so the HW-101 finals are bypassed for receive. I did it the simple way with an extra relay as QSK was not a requirement, since the SDR-1000 doesn't do QSK anyway.

      You'll also have to remember to switch the bandswitch on the HW-101!

      GL,
      -Pete
      WB2QLL
      Somers, WI










      -----Original Message-----
      >From: Justin Hall <kb7lak@...>
      >Sent: Feb 22, 2010 6:01 PM
      >To: softrock40@yahoogroups.com
      >Subject: [softrock40] finals from a tube rig?
      >
      >Greetings! I have a question. Is there anyway to build a SoftRock and then pipe that 1 Watt signal through something like a Heathkit HW-101, for example? If there is, I'll get on e-bay and get one right now. That was my first HF back in 1990 when I first licensed. I mean other than piping the audio through the MIC IN jack, is there any way to piggyback on the 6146 finals that make that rig so good? I'm awaiting the opportunity to really build a nice SDR and then have a good way to pump up the power in a more cost-effective way. Thanks for all the good advice you guys put on here. This is what ham radio is all about!
      >Justin L. Hall, Maj, USAF
      >Seoul, ROK
      >KB7LAK
      >
      >
      >
    • Brian Lloyd
      ... The 1962 Radio Amateur s Handbook has a very nice design for an amplifier using a single 6146A in grounded-cathode configuration. It requires about 1W of
      Message 2 of 9 , Feb 23, 2010
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        On Mon, Feb 22, 2010 at 7:54 PM, Hulen Smith <clay1952@...> wrote:
         

        Here's a link for using the HW-101 as an amp. However I'm not so sure you'd get enough drive using this particular mod even to the grids of the 6146's. It would be ok if you already had one to play with. However to buy one for this purpose, I'd doubt it would be worth it unless you wanted it as a secondary rig/standby. It is an interesting mod though for 5-10 watts of drive.

        The 1962 Radio Amateur's Handbook has a very nice design for an amplifier using a single 6146A in grounded-cathode configuration. It requires about 1W of drive for full output (90W input, about 50W output). One of my students is building it and combining it with his Softrock 6.2 board. The parts for the amp are coming from a couple of cast-off boat-anchors similar to the HW-101, i.e. an old Heathkit transmitter and an old Eico transceiver.

        I explained the project to the ham who donated most of the parts and his response I think tells the whole story, "That is just *SO* wrong, and *SO* cool!"


        --
        73 de Brian, WB6RQN/J79BPL

      • James Rogers
        Justin, remember the amp will have to be class AB. Tim/ N4XND ... From: Brian Lloyd Subject: Re: [softrock40] Re: finals from a tube
        Message 3 of 9 , Feb 23, 2010
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          Justin, remember the amp will have to be class AB.
          Tim/ N4XND
          --- On Tue, 2/23/10, Brian Lloyd <brian-wb6rqn@...> wrote:

          From: Brian Lloyd <brian-wb6rqn@...>
          Subject: Re: [softrock40] Re: finals from a tube rig?
          To: softrock40@yahoogroups.com
          Date: Tuesday, February 23, 2010, 2:30 PM

           


          On Mon, Feb 22, 2010 at 7:54 PM, Hulen Smith <clay1952@cmaaccess. com> wrote:
           
          Here's a link for using the HW-101 as an amp. However I'm not so sure you'd get enough drive using this particular mod even to the grids of the 6146's. It would be ok if you already had one to play with. However to buy one for this purpose, I'd doubt it would be worth it unless you wanted it as a secondary rig/standby. It is an interesting mod though for 5-10 watts of drive.

          The 1962 Radio Amateur's Handbook has a very nice design for an amplifier using a single 6146A in grounded-cathode configuration. It requires about 1W of drive for full output (90W input, about 50W output). One of my students is building it and combining it with his Softrock 6.2 board. The parts for the amp are coming from a couple of cast-off boat-anchors similar to the HW-101, i.e. an old Heathkit transmitter and an old Eico transceiver.

          I explained the project to the ham who donated most of the parts and his response I think tells the whole story, "That is just *SO* wrong, and *SO* cool!"


          --
          73 de Brian, WB6RQN/J79BPL


        • Jose A. Amador
          ... There is a simple solution, using passive grid drive. Using a 1:9 unun, loaded with two 910 ohms, 2 W resistors on the secondary, decoupled from the grids
          Message 4 of 9 , Feb 23, 2010
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            El 23/02/2010 15:47, James Rogers escribió:

            Justin, remember the amp will have to be class AB.
            Tim/ N4XND
            --- On Tue, 2/23/10, Brian Lloyd <brian-wb6rqn@...> wrote:

            From: Brian Lloyd <brian-wb6rqn@...>
            Subject: Re: [softrock40] Re: finals from a tube rig?
            To: softrock40@yahoogroups.com
            Date: Tuesday, February 23, 2010, 2:30 PM

            On Mon, Feb 22, 2010 at 7:54 PM, Hulen Smith <clay1952@cmaaccess. com> wrote:
            Here's a link for using the HW-101 as an amp. However I'm not so sure you'd get enough drive using this particular mod even to the grids of the 6146's. It would be ok if you already had one to play with. However to buy one for this purpose, I'd doubt it would be worth it unless you wanted it as a secondary rig/standby. It is an interesting mod though for 5-10 watts of drive.
            The 1962 Radio Amateur's Handbook has a very nice design for an amplifier using a single 6146A in grounded-cathode configuration. It requires about 1W of drive for full output (90W input, about 50W output). One of my students is building it and combining it with his Softrock 6.2 board. The parts for the amp are coming from a couple of cast-off boat-anchors similar to the HW-101, i.e. an old Heathkit transmitter and an old Eico transceiver.

            I explained the project to the ham who donated most of the parts and his response I think tells the whole story, "That is just *SO* wrong, and *SO* cool!"

            --
            73 de Brian, WB6RQN/J79BPL

            There is a simple solution, using passive grid drive. Using a 1:9 unun, loaded with two 910 ohms, 2 W resistors on the secondary, decoupled from the grids with a suitable capacitor (perhaps 1 nF at 250 V or higher) will be a quite near match 50 ohms in the primary and will ideally require 2.7 watts to deliver 50 V peak on the secondary, enough to drive fully the 6146's to some 70-80 watts. The match will degrade on the higher bands, when the reactance of the input capacitance of the 6146's starts to become comparable to 450 ohms. A more complex circuitry may give broadband compensation, absorbing the input capacitance in an input filter terminated in 450 ohms to a certain cutoff frequency, giving broadband 1:1 SWR. I don't know right now how high it could go that way, my gut feeling is that it looks a bit high termination resistance for too much bandwidth, I would have to calculate and model that and it is not that simple while I am "shooting from the hip" right now.

            I used that method for a pair of 4-400A loadad with 200 ohms on the secondary. 50 watts drive yielded 950 watts output on AB2.with no input tuning whatsoever,
            and perfectly stable on all bands.

            My calculations are for 2 x 6146's, class AB1, all the old drive circuitry disconnected, leaving only the biasing components.  But I wonder, are still there 6146's at a reasonable price nowadays?

            The outlined procedure may work as well for high gm horizontal output tubes, but 6KD6 / 6JS6 / EL509 and such are not that easy to locate lately...

            73,

            Jose, CO2JA


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