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Mains Transformers as Modulation Transformers

Discussion in 'Amplitude Modulation' started by G3YRO, Jun 7, 2020.

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  1. K5UJ

    K5UJ Ham Member QRZ Page

    You have a lot of questions that you can get answers to by searching on line and reading. Develop the habit of trying to find answers yourself. Some of these have to do with basics on transformer construction. Use youtube, wikipedia, etc.
    K4KYV likes this.
  2. N2DTS

    N2DTS Ham Member QRZ Page

    I do not really care, I thought others might want to know, or talk about transformer stuff.
    KI5HOC likes this.
  3. WZ5Q

    WZ5Q Ham Member QRZ Page

    I have found that very few people really want to know the internal mysteries of Magnetics. It seems that the knowledge of how and why things work is not a prerequisite these days, all they want is a picture of how to hook it up with expectations that it will operate correctly.
    KI5HOC likes this.
  4. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Regarding the topic of the TurboMod which brought up here as a side issue:

    As I said, my circuit is the same one with * designating the same phase as proven by looking at two oscilloscope channels simultaneously; and the 500/600 ohm winding is being used.

    So instead of doing the fanboy routine look at my schematic again and please tell me where disconnect is.

    Think I will ask WA1HLR to draw the dang thing out on a piece of paper... take a picture and send it.

    As I said earlier in post #26, a real schematic from Timtron would clear up a lot of mystery.


    Attached Files:

    Last edited: Jun 25, 2020
    KI5HOC likes this.
  5. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    It would appear that the 500/600Ω section would do nothing but add a few more turns to the turbo winding. This might increase the total ampere-turns in the section the DC is passing through, just enough to cause core saturation if a reactor/capacitor is not used.
    KI5HOC likes this.
  6. WB2GCR

    WB2GCR Ham Member QRZ Page

    A few things.
    Most of these answers are in the Radiotron Designer's Handbook. A free download now online.

    Laminations are indeed special alloys.
    Selected for their permeability and hysteresis curves, etc.

    Toroids of the power type are not powdered core, they are tape wound.

    As of now toroidal types do not work as gapped transformers.

    If you cut the core on any transformer you risk shorting the laminations together.

    Look into "C" cores - that's close to the same idea as cutting into a tape wound core.

    Yes, you can wind ur own power xfmrs easily (if you can buy the copper wire cheap enough)
    Several nice articles were in QST back in the day.

    There are formulas to determine everything including the number of turns and the wire gauge.

    Most are in the Radiotron handbook.
    Other places as well.
  7. WB2GCR

    WB2GCR Ham Member QRZ Page

    I think the schematic shown is valid.
    IF it did not work, something was not wired correctly OR there was a problem with
    the xfmr itself - or so it would seem?
    Many rigs are on the air with the "Timtron Turbo Mod" and sound fine.

    Question: did the mod iron operate properly when normally used and wired?

    (maybe try it first without the 500/600 ohm winding to verify operation?)
  8. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Whose rigs had this mod?

    The mod transformer operated properly before the mod and 600 ohm tap was tested as well.

  9. K5UJ

    K5UJ Ham Member QRZ Page

    I finally got time to watch the video. I am impressed that you are trying to build a push pull 810 final PA and are getting by with a bunch of power supply filter chokes in series to get a modulation reactor. Also that you saw the need for a transmit receive sequencing system and made one. I'll take your word for the fact that the Antek transformers can't have h.v. DC on them. Maybe that's why some who have tried to use them experienced discouraging results. I have never tried the 3 diode peak limiter. I've heard it doesn't work all that well. On some of my rigs I do put in neg. cycle loading, but that's just some reversed diodes off B+ to an anode impedance resistor to ground.

    I've always thought that the other methods by which the reversed diodes conduct over significant parts of the negative cycle, change the load impedance the mod. transformer sees which causes distortion. Maybe it is not that big of a problem.

    Good luck on the 810 PA. Maybe you can start another thread on what the problem is and we might be able to help you.
    K4KYV and W2BTK like this.
  10. W2BTK

    W2BTK Ham Member QRZ Page

    Just dusting this thread off. Bump.

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