The EFHW Transformer Redefined

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AF7NX, Jul 22, 2021.

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  1. WA7ARK

    WA7ARK Ham Member QRZ Page

    I have measured rate of temperature rise in the core of the ARRL/HfKits transformer I have been experimenting with, and using a 2 turn primary, constant RF power, the core temperature increases fastest on 40m, less on 20m and least on 10m, which I think is the opposite of what AF7NX said...
     
  2. KX4OM

    KX4OM Ham Member QRZ Page

    The original post is about redefining the EFHW transformer, not redefining the antenna wire and not the height of the antenna wire. I think the linked articles provided by AF7NX are very useful, and to me, some new information.

    Ted, KX4OM
     
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    Why worry about 0.5dB in the transformer when you can gain 3db by putting the radiating wire where it should have been in the first place. Too many that use this antenna end up with one end of the "dipole" a few inches above the dirt.
     
    Last edited: Jul 25, 2021
  4. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    The flux density cuts in half each time the freq is doubled.
     
  5. KX4OM

    KX4OM Ham Member QRZ Page

    My point is, Mike, that I am assuming as a point of discussion the height and positioning of the antenna is a solved problem. Putting the wire in the best configuration achievable. What remains is an optimization of the transformer problem. Less guesswork and more experimental data backed up with solid engineering analysis. The heat transfer problem for example. Ventilation or sinking.

    Ted, KX4OM
     
  6. K7JOE

    K7JOE Subscriber QRZ Page

    Doe
    Mike's comment - is well stated.
     
  7. K7JOE

    K7JOE Subscriber QRZ Page

    For less than half a dB you're better served to get on the air and make contacts. These antennas are a compromise and a one- half of one dB is not even perceptible.
    Waste of effort aside the engineering exercise for the sake of exercise. Does nothing from a practical standpoint of operating.

    The articles are interesting, certainly, and very well written. But the results are pretty much meh....in terms of finding a breakthrough or building any new mousetraps.
     
  8. K8JD

    K8JD Ham Member QRZ Page

    I moved to a pace where I have room for multiple wire antennas and have enjoyed having monobander antennas, like dipoles, EDZ and horiz loop antennas for most of the lower freq bands, also Yagis and vertiicals on the roof. . I had to take down a Butternut vertical when doorknob capacitor physically failed. I don't miss it.
    Not sure I want any more multi band, compromise antennas.
     
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    We are all so happy that you have room for things you like... but a lot of folks who come to this forum to learn about "compromise antennas" do not!
     
  10. K8JD

    K8JD Ham Member QRZ Page

    That's MY REASON for making the move !! :eek:
     

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