Saturday, February 18, 2012

The Improved Neophyte Receiver

Last year I decided to research a good receiver circuit for the 40 Meter band. I kept coming back to "The Improved Neophyte Receiver." The original Neophyte Receiver appeared in the February 1988 issue of QST on page 14 and written by John Dillon, WA3RNC. Over three years ago I bought a kit of parts for the "Improved Neophyte Receiver" from Dan's Small Parts. The article "Improved Neophyte Receiver" was written by Wes Baden, K6EIL. I ordered the circuit board from FAR Circuits. The partially built reciever board stayed incomplete in my junk box for a long time. I decided now was the time to finish it! I completed my build on January 29, 2012.

The first thing that I noticed was that I had my RF gain and Audio gain controls wired backwards. After I fixed that I noticed that the receiver had a real bad drift problem. I immediately asked for some help finding some new capacitors on the QRP-L mail list. Steve Smith, WB6TNL  came to my rescue with some nice NP0 capacitors for C2, C4, C5, C6, and C8. C8 evidently was the worst offender because as soon as I replaced that capacitor the frequency drift improved immediately! Before I replaced C8, the radio was just about useless. Now I can go make a cup of coffee and the radio is still on frequency when I get back to the shack. :)



Now I want to add some modifications to this receiver: a S-meter and a digital display. I will update my blog when those modications are complete.





7 comments:

  1. Hello Alan,congrats,nice project and improvement on it,
    coud you give me more details about L1 and L2 (how many turns ,wire,dimmentions) ernando@oil.com.br,tanks

    ReplyDelete
  2. Toledo,

    Sorry for the delay factor in replying to your question. I will also email you my answer.
    L1 = T-50-2 toroid. Sec. 26 turns #26 enameled wire, pri. 1 turn #26 closewound over bottom of sec.

    L2 = T-50-6 toroid. 22 turns #26

    Good luck on your build of the Neophyte Receiver!

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  3. Thanks for posting this. Do you really need both switches S1A and S1B? Or should I see one of these switches as part of one of the alternative connections?

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  4. Steve, thanks for stopping by the blog. The DPDT switch is so you can turn on/off the filter circuit. If you don't need the filter you can get rid of the switch and the entire filter circuit also. Let me know if you have any more questions.

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  5. I decided to build this rig, following your schematic. It works well on SSB and CW, though I find tuning to be more critical than I'd like. My rig struggles with AM signals though as there's a great deal of heterodyning going on and it's hard to hear much else. I'm sure I'll have fun in days ahead tweaking it and trying to improve it. Thanks very much for posting this schematic. It's a great project.

    ReplyDelete
  6. I decided to build this rig, following your schematic. It works well on SSB and CW, though I find tuning to be more critical than I'd like. My rig struggles with AM signals though as there's a great deal of heterodyning going on and it's hard to hear much else. I'm sure I'll have fun in days ahead tweaking it and trying to improve it. Thanks very much for posting this schematic. It's a great project.

    ReplyDelete
  7. Steve, you are welcome! Congrats on building a working receiver. It is always fun to tweak and improve a circuit. In my opinion, that is when the real learning begins!

    ReplyDelete