POSSIBLE QRZ LIBRARY OF TUBE RF LINEAR DESIGNS

Discussion in 'General Technical Questions and Answers' started by K4LRH, Aug 16, 2019.

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  1. K4LRH

    K4LRH Ham Member QRZ Page

    I know this is not a technical question but does QRZ have a library of tube RF linear amp designs ? I'm wanting to learn the pros & cons of push-pull and other proven [or not so good] designs.

    Thanks,

    Jack; K4LRH
     
  2. NN4RH

    NN4RH Premium Subscriber QRZ Page

    I don’t think QRZ keeps libraries, per se, but of course there are experts around the forums

    I might suggest getting ahold of an older ARRL handbook. At least for me,the older editions are easier for me to understand.

    Also if you are an ARRL member you can find articles in the QST archives.
     
  3. K7TRF

    K7TRF Premium Subscriber QRZ Page

    You're not likely to find a ton of tube based RF push pull power amplifiers as it's much harder to implement a good push pull RF design with tubes than it is a grounded grid design. I've seen some AM transmitter designs, mostly mono band or using plug in output coils to support multi-band operation that rely on push pull output stages but it's not nearly as common as single ended RF amplifiers.

    In the audio world where amps really need minimal distortion with conduction over the full cycle of the input waveform and there isn't a tank circuit to help restore signal integrity (and minimize harmonic components) you'll find a lot more push pull tube designs. Similarly push pull is much easier to implement when working with solid state components even at RF using broadband input and output transformers for signal splitting and combining. But there's not a ton of push pull tube based RF linear designs out there. Both the input and output circuitry gets more complex with push pull designs and tubes really have to be well matched not just for current sharing but for gain characteristics if you want to preserve linearity in a push pull design. Push pull also introduces concerns with crossover distortion that puts more stringent requirements on device biasing and again on device matching.

    There's a reason nearly every modern commercial tube RF linear relies on single ended designs with grounded grid topologies being the most common for external high power RF amps.

    FWIW, here's some good background information on RF amplifier designs:
    http://d1.amobbs.com/bbs_upload782111/files_26/ourdev_534474.pdf


    Here's some vintage info on push pull RF amplifier design, note the additional complexity compared to a GG architecture especially in the output network if you want to support multiple ham bands:
    https://www.americanradiohistory.com/Archive-Radio/30s/Radio-1934-12.pdf
     
    N7UJU likes this.
  4. K4LRH

    K4LRH Ham Member QRZ Page

    Thanks, you've answered several of my concerns. Thanks also for the websites.

    Jack
     
  5. KJ4YEV

    KJ4YEV Premium Subscriber QRZ Page

  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    In at least the first 2 of the ARRL Single Sideband for the Radio Amateur manuals, virtually all of the linear amplifier designs utilize push / pull designs and not the now "standard" parallel tube designs. The 1st edition is copyrighted 1954 and the 2nd edition is copyrighted 1958. I do have copies of both editions.

    Glen, K9STH
     
  7. W1VT

    W1VT Ham Member QRZ Page

    In the old days few hams had access to a spectrum analyzer to evaluate key performance issues like intermodulation distortion, but now you can buy perfectly serviceable new instruments for under a $1000.
    Now may be a great time to conduct your own measurements at relatively low cost.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

  9. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    theres plenty of old handbooks to download as pdfs
    1939, 1941, 1959, 1968
    That american radio history website has a wealth of info
     
  10. KL7AJ

    KL7AJ Ham Member QRZ Page

    Push pull has the most advantage at VHF and higher, since the overall plate capacitance is less....the plates are essentially in series, rather than parallel. However, the circuitry is a bit more convoluted, requiring separate neutralization for both tubes. The Hazeltine neutralization scheme was one of the most effective for this.
     

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