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Re: Miniboots amp idea using Mobo minifilters

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  • ke4id
    Hi, John, I built an 80M/40M Ensemble RXTX earlier this year. The initial power power boost comes from a HEXFET amp shown in Experimental Methods in RF
    Message 1 of 18 , Mar 2, 2011
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      Hi, John,
      I built an 80M/40M Ensemble RXTX earlier this year. The initial power power boost comes from a HEXFET amp shown in "Experimental Methods in RF Design" by W7ZOI and company. It is on page 2.36, Figure 2.98. It is forward biased to draw 100 mA for SSB use.

      I added a negative feedback loop from the gate to the drain, consisting of a 4.7 k resistor in series with a .1 uF cap, to cure some instability. Measured gain is 18db.

      Here is the total SDR setup:
      -Outboard Control Module: this was built to externally key the SoftRock, two amplifiers and the input to the sound system. Parts were soldered to the tin project box, purchased from Michael's. Solder lugs were also used.

      -HEXFET amp with built-in relay. This is keyed by the Outboard Control Module. This is also in a tin project box.

      -Outboard Low Pass Filer for 80M (my band of interest these days). This small unit is in an Altoids box.

      -Ameritron AL-811H tube amp. This is also keyed by the Outboard Control Module.

      -A foot switch is used for the PTT function.

      -Connections are via BNC jumpers. I get about 140 watts out on SSB. It works great on AM, too.

      A critical feature to turn on in PowerSDR v1.19.3.15 is the TR sequencing. This can be found in the tool bar: Setup-->General-->Options--> check the box for Enable X2TR Sequencing. I use an X2 delay setting of 60.

      Best regards,
      Jack



      --- In softrock40@yahoogroups.com, John Williams <KE5SSH@...> wrote:
      >
      > I have an Ensemble RXTX 40/30/20 that I want to boost the power a bit ........
      >
      > John Williams
      > WQKA523
      > KE5SSH
      >
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