Question E9C12:
Which of the following describes an extended double Zepp antenna?  

Choices:  
A: An end-fed full-wave dipole antenna  
B: A center-fed 1.5-wavelength dipole antenna  
C: A center-fed 1.25-wavelength dipole antenna  
D: An end-fed 2-wavelength dipole antenna    

Correct Answer is  C: A center-fed 1.25-wavelength dipole antenna  

To identify an extended double Zepp (EDZ), remember: it is a “double Zepp” (two legs, center-fed) that’s “extended” beyond a half-wave per leg.

Why the correct answer (C) is correct:
- An EDZ is a center-fed wire whose total length is $1.25\lambda$.
- Each leg is $0.625\lambda$ (5/8-wave), giving some broadside gain over a half-wave dipole (about 2–3 dB).
- Hence: center-fed 1.25-wavelength dipole antenna.

Why the other choices are incorrect:
- A: End-fed full-wave dipole (1.0λ, end-fed) — EDZ is center-fed and longer (1.25λ).
- B: Center-fed 1.5-wavelength dipole (3/2-wave) — that’s not the EDZ geometry; different length and pattern.
- D: End-fed 2-wavelength dipole — wrong feed (end-fed) and wrong length (2.0λ).

Useful formulas and rules of thumb:
- Total length: $L_{\text{EDZ}} \approx 1.25\lambda$
- Per leg: $L_{\text{leg}} \approx 0.625\lambda$
- In feet (free space): 
  - $$L_{\text{EDZ}}(\text{ft}) \approx \frac{1230}{f_{\text{MHz}}}$$
  - $$L_{\text{leg}}(\text{ft}) \approx \frac{615}{f_{\text{MHz}}}$$
  - Practical builds often shorten a few percent for end effects.
- Feed: High and reactive feedpoint impedance; typically fed with balanced line and a tuner.
- Pattern: Stronger broadside gain and narrower main lobes than a half-wave dipole; multiple sidelobes appear as length increases beyond $1/2\lambda$.