Vertical radials in spiral circle

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N1IPU, Jan 12, 2021.

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  1. N1IPU

    N1IPU Premium Subscriber QRZ Page

    Had QSO last night and was discussing radials on vertical antennas in limited space. Operator said his field was laid in concentric circles due to limited space. Had a great signal which when switch to dipole he fell into the noise. Layout like this
    Take note just referencing layout here.

    Just curious what you all think of this idea? I used galvy fencing before which has worked well for me but this idea you could lay out multiple bands in a very small space.
    K0UO and AK5B like this.
  2. M0AGP

    M0AGP Ham Member QRZ Page

    My intuition around how radials work is that they are trying to approximate a conducting plane.

    From a physics point of view the monopole above a uniform conducting plane possesses rotational symmetry about the vertical axis where the monopole resides.

    Therefore all RF currents must also possess this symmetry and as a result all currents must flow “radially” either directly away from the monopole or directly towards it.

    This is why radial wires are a good approximation geometrically to the conducting plane.

    Fencing should work, as there are still pathways where rf currents can flow away from the monopole.

    I wouldn’t expect a spiral to be very optimal, as the RF then needs to travel a much longer pathway. I suspect that having short radials out to the edge of the spiral would work as well as the spiral.

    And if he used the same amount of wire as he used in the spiral, I expect many short radials would work better than his spiral radials do.

    The vertical beating the dipole is a giant Pandora’s box I shall not open!
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  3. RW4HFN

    RW4HFN Ham Member QRZ Page

  4. AI3V

    AI3V Ham Member QRZ Page

    Yes, different physical shape antennas will have different radiation patterns.

    Nearby objects- like your house- will have a significant and unpredictable effect.

  5. M0AGP

    M0AGP Ham Member QRZ Page

  6. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    There is a special class of stations called "Traveler's Information Stations" (TISs) on the old AM band in America. The rules of this service, which limit such stations to very small antennas (in terms of wavelength) are intended to limit the radius of such stations to something along the lines of a quarter- to a half-mile. Most if not all of them use vertical polarization since the target is automobile radios.

    Most, if not all of the ones in Austin have badly compromised radial systems, and can only be heard, even by the serious AM DXer, at the range of four or five miles. However, there is one in Austin which can be heard at my house during the day, with the ferrite rod of a good old-fashioned AM/FM transistor portable, at a distance of 18 miles, although of course it cannot compete with Radio Enciclopedia at night.

    I asked a ham radio acquaintance who was also a professional broadcast engineer why this station had such a wide range compared to the others using the same power and antennas. He told me that instead of using very short (in terms of wavelength) radials like most TIS builders, the guy who constructed the "blowtorch" one used full-sized 1/4 wave radials, laid out in a spiral.
    Last edited: Jan 12, 2021
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  7. AK5B

    AK5B Ham Member QRZ Page

    I like the idea of spiraling radials although I believe as configured would be less than optimal compared to the same monopole with the standard spoke pattern---but if the difference is small it may be a godsend for hams in small antenna spaces.

    An in-between version might be the better way to go with the shorter radials going out radially and the longer radials beginning their spiraling at that point just beyond (not sure if this is logistically possible with more than one longest radial, though, as others might have to cross each other which as we all know is a big no-no).

    At any rate I think it would be cool to do a A/B comparison and see what the difference actually is in overall performance. Thanks to the OP for posting an interesting and thought-provoking idea.

    I think the spiral version could be called the "Hemi-TakTenna" Monopole (as Mr. Marconi spirals out of control in his grave).


    K0UO and M0AGP like this.
  8. KD0CAC

    KD0CAC Ham Member QRZ Page

    Looking for options , RV park - very little space for radials .
    I just assume [ that's looking for trouble ;) that anything that does not go with conventional antenna theory - smaller , lower etc. is a compromise - so the Rx & Tx signal is compromised .
    Example an HT antenna is very close to a dummy load , even those can receive & send but to a limited amount .
    WB5YUZ likes this.
  9. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    There is a reason why they are called RADIALS and not CONCENTRICS or SPIRALS. :)

    -No advantage to complex patterns.

    -The difficulty in trying to install such a field is mind boggling.

    -If obstacles or limited space are factors, just terminate the radial as necessary. Install more radials to compensate.

    Easy to read. Real world examples and measurements. Drink deep.
    Rudy Severns, N6LF

    Classic book covering antennas and radial systems. FREE download. Paper copy available from Lulu or Amazon. Get this for your long term library.
    Edmund Laport; Radio Antenna Engineering, 1952

    Direct PDF Download, no registration.
    Last edited: Jan 12, 2021
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  10. AK5B

    AK5B Ham Member QRZ Page

    I almost added "Everything works; it's all a matter of degrees as to how well something works"


    "There is nothing new under the sun"

    to my earlier post. Sometimes, or rather often, some things are just too good to be true.;)
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