Zepp, exteded Zepp, double extended Zepp?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AA7EJ, May 19, 2016.

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  1. AA7EJ

    AA7EJ Ham Member QRZ Page

    What are the correct / common used names ( if any) for these length of Zepp configurations?

    Zepp - end fed half wave (dipole)

    extended Zepp - end fed 5/8 wavelength radiator
    extended Zepp - end fed 1 1/4 wavelength radiator

    double extended Zepp - center fed 2x 5/8 wavelength radiators
    double extended Zepp - center fed 2x 1 1/4 wavelength radiators

    73 Shirley
  2. KA0GKT

    KA0GKT Ham Member QRZ Page

    Technically, a Zepp (or Zeppelin) antenna is an end-fed 1/2-wave antenna fed through a 1/4-wave matching section (If this sounds like a J-Pole, that's because a J-Pole is a Zepp); so physically, a Zepp is 3/4 of a wavelength long.

    An Extended Double Zepp (EDZ) is a center fed 2x 5/8 (1-1/4 total) wavelength, but the way the phasing works out, it is actually like a pair of collinear half-wave antennas separated by 1/4 wavelength. It is the greater element separation which increases the gain over the typical collinear.
  3. AA7EJ

    AA7EJ Ham Member QRZ Page

    So if it is fed with 450 ohms ladder line terminated with 450 ohms balanced tuner the 1/4 wave stub would not be necessary, hence the "real" Zepp is still only 1/2 wavelength long.
    I am not sure if a matching stub should be counted as radiator lenght since its function is not to radiate anyway.

    Granted 450 ohms feed line is just commercial convenience, higher impedance ladder line would work better.

    Again, such separation stub should not be described as an active part of the antenna and whole setup should be fed at the end. Than it should not be called EDZepp but collinear 5/8 radiators as you pointed out.
    So far I have not seen EDZepp fed at the end.

    Woops, the "reply" did not formatted the text the way I wanted , sorry.
  4. KC8VWM

    KC8VWM Ham Member QRZ Page

    But the attached stub is a part of the "active" antenna.

    KA0GKT likes this.
  5. NL7W

    NL7W Premium Subscriber QRZ Page

    As far as I know, the stub doesn't radiate, or supposedly doesn't in theory? It provides a means of matching.
    I wouldn't consider that "active," but this could all be semantics.
    Last edited: May 19, 2016
  6. K9STH

    K9STH Ham Member QRZ Page

    A true Zepp is an end fed antenna 1/2-wavelength at the lowest frequency. It is not a dipole! This antenna works very well at the "powers of 2" times the lowest frequency.

    That is 2^0 = 1, 2^1 = 2, 2^2 = 4, 2^3 = 8, 2^4 = 16, and so forth. For example, a Zepp cut for 160-meters works very well on 80-meters, 40-meters, 20-meters, and 10-meters. But, a Zepp doesn't work well at other multiples such as on 15-meters which is 12-times the original frequency.

    Many years ago, I had a Zepp cut for 160-meters. That antenna worked very well on 160, 80, 40, 20, and 10-meters. However, not at all for 15-meters. But, I had a 2-element yagi for 15-meters so I did not have to worry about that band. Although the WARC bands were long in the future, had they been in existence, at that time, the Zepp would definitely not worked well on any of those bands.

    Glen, K9STH
  7. NL7W

    NL7W Premium Subscriber QRZ Page

    Nice to know!
    My initial reaction: This appears to be the case because of the lower to high impedance stub transformation, and its general maintenance for the mentioned multiples, eh?
    Have a good weekend, Glen.
  8. K8JD

    K8JD Ham Member QRZ Page

    What do I Call IT ?
    I use an extended double 20M Zepp, but it is fed with a random length of 450 Ohm twinlead (I match it to the transmitter with a MFJ974 balanced line tuner) so I guess it is not a real Zepp.
    It's a double 0.65 wave ceterfed antena on 20M.
    It is also a double halfwave centerfed on 30M and a halfwave dipole on 60M (roughly). .
    On 40M it is a 3/4 wave dipole.
    Seems to work fine on several bands.
    It had a decent bidirectional gain on 20M.
  9. NL7W

    NL7W Premium Subscriber QRZ Page

    Center-fed dipole resembling an EDZ on 20M. :)
  10. AA7EJ

    AA7EJ Ham Member QRZ Page

    I would suggest to look-up (mathematical) definition of dipole antenna.

    My initial question was about various configurations / definitions of antenna commonly called Zepp.
    If it is 1/2 wavelength long it is given that it will "work" on certain harmonic frequencies no matter what we call it or how we feed it. But now we are getting off the original subject.

    It looks as 1/2 wavelength radiator fed at the end can be called "true Zepp".

    So if we feed DEZepp or collinear array in center calling it Zepp it no longer follows the "true Zepp" - end fed setup.

    Just to make sure - I am not looking to split hair , just looking for some consistency.

    I believe the EDZepp current distribution in the stub ( post #4) is incorrect - may have wrong phasing relations to main radiator.
    Any modeling software should show current in the stub and antenna.
    I currently do not have one handy.

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