ad: Radworld-1

My impoved mystery crystal set by G0CWA

Discussion in 'Homebrew and Kit Projects' started by G0CWA, May 9, 2012.

Thread Status:
Not open for further replies.
  1. G0CWA

    G0CWA Ham Member

    Hi as suggested by one of the forum members I have descided to present my home made radios as shown on http://makearadio.com/index.php The first of many I am going to show you is my version of the mystery crystal set with both improved sensitivity and selectivity.

    For a full write up and building instructions check http://makearadio.com/visitors/nick-mystery.php basically I have built a standard set but with an unusual twist to improve its perfomance.

    [​IMG]

    I hope you find this set worth your interest, or even having a go at yourself.

    I made the tuning scale by printing onto a printable mirrored cd and the tuning pointer is a small clock hand on the capacitor shaft

    Happy building and 73 for now Nick G0CWA
     
  2. AF6LJ

    AF6LJ Ham Member

    That is very, very cool.
    Makes me want to build one.
     
  3. G0CWA

    G0CWA Ham Member

    Why not have a go Sue?
     
  4. AF6LJ

    AF6LJ Ham Member

    It's been a project on the back burner for a while.
    An ex-coworker gave some galania (sorry spelling) from his families mine in Idaho.
    The plan has been to mount peaces of the crystal and build a crystal set.
     
  5. KO6WB

    KO6WB Premium Subscriber

    Hi Nick, well another great posting and it got Sue's attention which is good.
    Sue needs to check out some of your other offerings like the mechanical audio amplifier using a carbon rod. That was really neat.
    73
    Gary
     
  6. G0CWA

    G0CWA Ham Member

    Hi Sue

    OK about the galena, but if you do build one put a small signal diode, eg an 1N34A in as well to tune in the stations first before setting the crystal detector it makes things alot easier mine is hidden under the board all you need to do to bring it into play is put the whisker on the brass drawing pin. Also mount the galena pieces in woods metal or low melting point solder usually available from model making shops to solder white metal castings.

    No Gary it is not cheating to use a diode as well!
     
  7. KO6WB

    KO6WB Premium Subscriber

    Okay Nick.....but with a 1N34A you don't get to play with the contact whisker. Some times you can get it to surpass the sensitivity of the 1N34A. Other times... well try again. There have been tricks with the diodes to get them more sensitive. Applying a bias voltage to them works well but that is definately cheating.
    Have fun
    73
    Gary
     
  8. WX7G

    WX7G Ham Member

    I especially like your carbon beam amplifier.
     
  9. G0CWA

    G0CWA Ham Member

    From the nice posative comments I can see the carbon amp should be the next one! thanks. I'll post it in a few days. Thank you for all the comments.

    73 for now Nick G0CWA
     
  10. W4HAY

    W4HAY Subscriber

    Sue, if you'd like, I can drop a microwave diode in the mail to you. I've gotten much better results with them than the 1N34A.

    Neat idea! Now we wanna see the back of the set.

    I have a set with a Tuggle front end, and solenoid and spiderweb coils on sliding tracks. One of these days maybe I can get picture of it. I also have a 76 tube on a wooden base that connects to it as a grid leak detector.
     
  11. W4HAY

    W4HAY Subscriber

    Even if you derive the voltage from lemons, strips of copper, and iron nails?

    Some have used a second set tuned to a nearby "blowtorch" to derive the bias voltage.
     
  12. AF6LJ

    AF6LJ Ham Member

    I have everything else save for the earphone and I know where to get that.
    Sure :)

    A nd yes...
    I know not to check it with an ohmmeter.
    :D
     
  13. K1ZJH

    K1ZJH Ham Member

    As a point of interest, the old microwave diodes in the ceramic cases dating back to WW11
    are silicon devices.

    I'm not convinced adding bias is "cheating." Carborundum detector assemblies included
    a battery and rheostat for optimizing the detector.

    Pete
     
  14. G0CWA

    G0CWA Ham Member

  15. W4HAY

    W4HAY Subscriber

    I noticed that link after it was too late to edit my post. Black and blue text are difficult for my eyes to differentiate between on this old Trinitron monitor.

    Sue, these diodes show a Vf of about 0.28 Volts. The one I'm sending picked up a couple of signals in the 41 Meter band on my "Tuggle Tuner" set.
     
  16. G0CWA

    G0CWA Ham Member

    No problem I understand I was in the same position until I descided to udate my monitor

    73 de Nick G0CWA
     
  17. KO6WB

    KO6WB Premium Subscriber

    There have been quite a few experiementers that have reported better results with the Galena and cat whisker setup than any commerical diode. I'm not sure that's true and the Galena approach can be a pain at times. As for applying bias from lemon juice, rusty nails or another crystal set I would guess that's fine as long as you are experimenting. Even in that aspect using a battery would be okay, it's just not a straight detection method. For a crystal set adding an amplifier to bring the audio up is defeating the purpose of a simple unit but it is fun to do.
    Just have fun
    73
    Gary
     
  18. W4HAY

    W4HAY Subscriber

    There's another little trick that lets you copy CW. Place an oscillator near the crystal set and tune it to the frequencies of interest. A signal generator fed into a solenoid or spiderweb loop for coupling works well. It's effectively a BFO and I've copied very strong signals on 80 and 40 by doing this.

    I discovered this after I'd built a tone-modulated oscillator for the BC band to calibrate my sets. I had the tone turned off and as I swept near the frequency the crystal set was tuned to, I heard numerous faint hetrodynes, each corresponding to a BC station. It seemed to work best with the oscillator placed a foot or more from the crystal set. The oscillator was written up in the September '05 XTAL Set Newsletter.
     
  19. AF6LJ

    AF6LJ Ham Member

    Thank you the diode showed up in the mail this morning. :)
    Happy
    Happy
    :)
     
  20. G0CWA

    G0CWA Ham Member

    Hi Sue

    How's the set going?

    Nick
     
Thread Status:
Not open for further replies.

Share This Page