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Re: Simple transceiver - more details

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  • ltj_designs
    Here is more information on the design (see block diagram below) switch MAX4544 analog switch. It could be done with PIN diodes, but the MAX4544 circuit is
    Message 1 of 10 , May 30, 2006
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      Here is more information on the design (see block diagram below)

      "switch"

      MAX4544 analog switch. It could be done with PIN diodes,
      but the MAX4544 circuit is so simple. The cw key switches the
      DDS60 signal from the Softrock 40 to the buffer amplifier.
      "OFF" isolation is greater than 50 dB. Seems enough to avoid
      backwave. Has about 1.5 insertion loss.

      "buffer"

      IFR510 MOSFET amplifier running in class C. I am using the NB6M
      Miniboots amp, without the antenna switching or input drive
      adjustment network. The buffer supplies about 10 dBm and can
      actually produce 5 watts on its own. However, it is asked only
      to provide about 400 mw. This circuit was chosen because, with
      the addition of a gate bias circuit, it can be adjusted for
      class AB operation. When a suitable SSB generator is available,
      the same amp can be used.

      "4W amp"

      This is the HF Projects PA-100 amplifier project kit. It also
      provides about 10 dB gain and is linear. With extra cooling, it could
      deliver over 15W.

      "LPF"

      A manually tweeked Cauer filter.


      Andy WA3LTJ



      --- In softrock40@yahoogroups.com, "ltj_designs" <arm@...> wrote:
      >
      > I am looking for comments on a simple transceiver based on the
      > SoftRock 40. It looks something like this:
      >
      > Simplified block diagram for cw transceiver
      > based on DDS60 and SoftRock 40
      > (Best viewed with fixed space font, e.g. Courier)
      >
      >
      > computer -----------
      > | |
      > | --->SoftRock 40<------------------
      > | | |
      > | | |
      > DDS60-->switch-->buffer-->4W amp-->LPF-->T/R relay-->antenna
      > ^
      > |
      > |
      > cw key
      >
      > Note, I have all the components built and tested individually.
      > One thing that would make it more interesting is to have a program
      > like Bob WA6UFQ's DDS VFO Controller upgraded for transceiver
      > operation.
      > It would have a "Transmit" push button:
      > Toggle "Transmit" ON to set the output mode to X1 and activate
      > a LPT port bit (for the T/R relay).
      > Toggle "Transmit" OFF to return to X4 or X8 for the SoftRock.
      >
      > The alternative is to program a PIC with LCD. Is that more
      desireable?
      >
      > Andy WA3LTJ
      >
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