TheRadioBoard

Looking at old posts I came across Crystalset Q-multiplier, Oct 30, 2009. Intrigued with the single cell design I tried and failed badly to make it work(oscillate) across the BC band. I used recommended semiconductors with an unloaded LC ckt, i.e. no detector diode. High end OK, that is it! Has anyone worked on this Lambda ckt with sucess or what? I need info! cheers john85

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jn85

Looking at the original article, it may be you don't have enough Q lower in the band. You might try different FETs, though.

EDIT: Here's the original thread: http://theradioboard.com/rb/viewtopic.php?t=2242

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

Thanks for your response, but I did try a total of 12 fets and 12 pnps combos with equal results. I am hoping for more responses, I do have the original post!Thanks again. john85

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jn85

I posted the link so others could find it without having to search.

In regen sets we experience the effects of higher reactances as you tune higher in frequency. A regenerative stage will oscillate with less feedback at higher frequencies because the voltage induced across the tuned circuit is higher. It sounds as though you're running into the same problem. If you can't improve the Q, you might try decreasing the LC ratio (less L, more C), so the reactances are higher across the band.

If no one who's built this circuit jumps in, try contacting the original poster. He hasn't been on here in a while, but a PM or email might get a reply.

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

hey John -- if you do PM or email Don Peters, please share his reply. That circuits' been on my "to try" list for awhile so I'd be interested in what you find out. I'm sure others would to.

You've probably already Googled the lambda diode work of Ramon Vargas-Patron. If not, he has done a fair amount with that circuit and may have some hints in his writings. (He answers emails too).

Good luck and keep us posted - sorry I can't help.

73, Dan