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23025Re: A little Regen help please

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  • qrp.gaijin
    Mar 1 5:26 AM
      In regenrx@yahoogroups.com, <david.newkirk@...> wrote :

      BTW, an aspect of the Armstrong (plate-tickler feedback) circuit that 
      > I keep intended to get around to exploring is as follows: I happen to 
      > think that a REGENERATION capacitor capacitance of only a few 
      > hundred picofarads--commonly we see 140 pF or less--is far too low. 
      > If the REGENERATION control is really acting as a variable _bypass_ 
      > capacitance

      [...]

      > I suspect that a large feedback-control capacitance on the order 
      > of multiple parallelled broadcast-variable sections would result in 
      > significantly less tuning change as feedback is adjusted

      Two links that may be of interest to you in connection with this investigation.

      1. Proposed explanation of throttle capacitor operation as being due not to variable RF bypass, but instead due to Miller capacitance and negative feedback: http://www.theradioboard.com/rb/viewtopic.php?t=4516 .

       

      2. Reducing frequency shift with regeneration adjustment (above threshold) by separating the regenerative amplifier and the detector and keeping the amplifier operating in class A: http://theradioboard.com/rb/viewtopic.php?f=1&t=5153 . The key observation being that: (quote by vladn) "In a system with linear losses and linear amplification there is no Gm change required to sustain an arbitrary amplitude. [...] Gm changes only during the transition from the amplitude A1 to the amplitude A2. But the stationary values of Gm_A1 and Gm_A2 are equal (or nearly equal in a practical linear circuit)."

      Best regards,
      qrp.gaijin@...

      P.S. I've been hoping for a while you would update your enticing page at http://dpnwritings.nfshost.com/ej/regenerative_receiver/ . Any plans to do so? :-)

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