Tetrode dipper (GDO).

Discussion in 'General Electronics Chat' started by ian field, Mar 25, 2015.

  1. ian field

    Thread Starter Distinguished Member

    Oct 27, 2012
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    My google mojo is dragging its feet a bit lately.

    Having found a small stash of VHF tetrodes in the junk box, it occured to me that the famous tetrode kink would be perfect for a simple GDO with an untapped set of coils.

    Searches for "tetrode oscillator" and "tetrode dipper" are not producing much in the way of relevant results.

    Thanks for any help.
     
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    You might check amateur radio archives for "electron coupled oscillators"
     
  3. ian field

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    My hazy reccolection thinks "electron-coupled" has something to do with tubes having more grids than a pentode.

    Something like an ECH82 for example - the second grid is actually the anode for the triode section oscillator stage, this grid (anode) is of course in series with all the other grids in the hexode and the oscillator signal is coupled into the electron stream that finally reaches the anode proper.
     
  4. KL7AJ

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    They sometimes did use pentagrid converters for this, but any tetrode will work. Also check out the "tri-tet" oscillator, affectionately known as the "rock crusher." :)
     
  5. ian field

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    I was really homing in on the tetrode oscillator because its easy to make the negative resistance oscillate just by adding a bare minimum LC tank - that and I found a small stash of 6CY5 VHF tetrodes in the junk box.
     
  6. KL7AJ

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    By the way, when you're building your sampler coils, make them large diameter and fat. My old Navy Surplus AN-PRM-10 GDO is so much better than anything else out there because of the aspect ratios of the coils. Short and fat wins!
     
  7. KL7AJ

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    http://en.wikipedia.org/wiki/Dynatron_oscillator
     
  8. ian field

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  9. BR-549

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    Sep 22, 2013
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    ian...."Electronic Communication" Shrader second edition has an excellent explanation and several examples of the tetrode dynatron.
     
  10. alfacliff

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    the second grid (screen grid) isnt a second plate, it is for accelerating the electrons to the plate and repelling secondary electrons back to the plate.. the penta grid convertor tube was never used in GDO's. mostly tripde tubes were used. when you get right down to it, any tube or transistor with gain can ve used as a GDO except for specialized tubes like klysterons, magnetrons, thyratrons, rectifiers and such.
     
  11. ian field

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    Never said a frequency changer was ever used in a GDO did I!

    I wouldn't actually know - but no doubt someone somewhere has probably tried it.
     
  12. ian field

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    Somehow that seems like common sense to me - although I've seen a kit advertised (now discontinued) that used a motley assortment of commercial inductors as the sampler coil, they ranged from those wire ended RF chokes that look similar to resistors.

    The manufacturer claims they discontinued it because suitable coils were becoming unobtainable - IMO it wouldn't have been much good using those types of coils.
     
  13. alfacliff

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    the penta grid converter tube was mentioned in #3 and 4.. in number 3, it is called a heptode. if you would like some ways others have made GDO's here is a link to kit manufacturers, heathkit and eico made kit form GDO"s.
    http://www.nostalgickitscentral.com/
     
  14. ian field

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    But I never said it was used in a GDO, did I!

    You really should read a post first if you're going to reply to it.

    Just to help you out: someone mentioned electron coupled oscillators, and I mentioned that I thought that was the general idea of a frequency changer valve.
     
  15. ian field

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    The GDO has been a "back burner" project for a while, the mechanical stuff is a bit of a downside, so I really need a bright spark of inspiration so I can get started.

    Its a bit of a balancing act - using a tetrode should be dead easy and I have some. OTOH; a valve design means a bit more effort on the PSU.

    As yet I haven't ruled out solid state, the No1 priority is finding a design that uses simple untapped coils.
     
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