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Parasitic Suppresser

Discussion in 'Amateur Radio Amplifiers' started by KA5ROW, Jun 13, 2012.

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  1. AB1QP

    AB1QP Premium Subscriber QRZ Page

    Would it be too much to ask that you start your own thread, maybe titled "6K Groupies unite" or " Dont stop believin'"
    Even good sex just becomes friction if it goes on too long.

    AB1QP
     
  2. G0HZU

    G0HZU QRZ Member

    At the risk of sounding like a stuck record, Rich I do think it would be useful to revisit the subject again in 2012 using modern analysis tools.

    The reason I suggest another 'parasitic revisit' is because I do think that a modern analysis would show up other (potential) methods to enhance stability that would compliment the classic RL suppressor. It would also explain the suppressor theory much better than what is out there at the moment.

    I have the tools and general RF design experience but sadly I don't have any hands on experience of big tube amplifiers like you and the other people here. So that makes me a less than ideal candidate to present a more up to date 'revisit' on my own.

    What is particularly alien to me is the attitude on here to my attempts to try and push for this fresh look. You see, I work in an environment where it is seen as healthy to question and debate stuff. Nobody really minds if someone corrects someone's design or theory error because we all KNOW that none of us holds all the answers. However, if we pool knowledge and don't get hung up on who was right or wrong on Thursday's debate then everyone benefits from knowing the correct answer.

    That's how it happens where I work. We peer review each other's designs and criticism is positively welcomed.

    Here any criticism seems to be life threatening to overly sensitive, over inflated egos. It isn't healthy :(
     
  3. AB1QP

    AB1QP Premium Subscriber QRZ Page

    It's the pubescent snark thats annoying, not the critique or attempts to revisit the subject.
     
  4. AG6K

    AG6K QRZ Member QRZ Page

     The article "Parasitics Revisited" (Sept., 1990 QST) needs a follow-up article. Unfortunately I fear some QST advertisers would interfere if I sought to publish it in QST - which means I am obliged to publish it on the Web.
    • A valid explanation of how a VHF oscillation suppressor works is that it simply reduces VHF amplification by reducing the parallel-equivalent VHF load-R presented to the anode at the anode's parasitic resonance so that there is not enough VHF amplification to support VHF regeneration.
    • I find this saga somewhat amazing because it happened because amplifier designers chose to summarily dismiss the C-feedback figure in amplifier-tube mfg. spec sheets because they thought it was too small to matter -- which was true at HF -- but Xc wasn't all that small at VHF/UHF. . . It was a nasty combination of hubris and Murphy's Law.
    cheers.

    postscript:
    Eimac's Willis B. Foote was right in saying we build amplifying devices, it's up to amplifier designers to make them stable.
     
  5. AG6K

    AG6K QRZ Member QRZ Page

     It's never too much to ask Frank - but I choose not to vacate at this time. Perhaps you should take this up with the person who is forcing to read this thread. cheers
     
  6. AG6K

    AG6K QRZ Member QRZ Page

     Not an exact science is right Sue. Toyota experienced a mysterious problem with the computers in their Prius. Sometimes something would switch on the transistor that controls the engine throttle - and you were off to the races. In my opinion the cause could be background-radiation. Nissan had this figured out long ago when they added throttle-down command whenever the anti-lock brakes were applied. This allowed the owner to stop the runaway vehicle without having to think to shift into neutral when the throttle was stuck wide-open.

    cheers
     
  7. G0HZU

    G0HZU QRZ Member

    Yes, but I was thinking along the lines of a demonstration of what causes the problem (at system level) using a basic model and also some simple calculations to calculate the new value of anode impedance once the suppressor gets added and also how much the suppressor shifts the anode resonance slightly down in frequency. Also a demonstration of how limited the suppressor is in terms of bandwidth and how varying the L and R values can demonstrate the optimal choice of R and L for a given scenario. The sums to do all this are very simple. No big equations or scary theory needed.
     
  8. W1BR

    W1BR Ham Member QRZ Page

    Jeremy, a lot of your comments towards JI seemed to be asking HIM to validate your opinion.
    You might do better doing the research, and presenting the facts in a website presentation to
    support your position. This endless discussion about JI and others isn't proving the science one
    way or the other.

    Pete
     
  9. N3JBH

    N3JBH Ham Member QRZ Page

    Rich why not do it here on QRZ ? This site seams more receptive towards you then say EHAM. So it be good to see it posted on a site like this where several folk's visit it. And who knows maybe it get rave reviews and compliments?
     
  10. AG6K

    AG6K QRZ Member QRZ Page

     Good idea Allan. E-Ham is an incorrigible good ol' boys club. My guess is that the article will be short.
     
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