EZ-NEC seems not to match the Antenna Book?
 

In the 1976 edition of the ARRL Antenna book, at page 147 I see a graph (Fig.
4-37) showing the gain of a two-element array consisting of a driven element and
a self-resonant parasitic element (i.e. same length as driven element, no
de-tuning).

The graph shows gain (in the two orthogonal directions) as a function of
spacing. For spacing = 0.14 wavelength, the graph shows a bi-directional gain of
about 4 dB (and then a front-to-back ratio of 0 dB).

Unless I did something wrong, on EZ-NEC the same array with 0.14 WL spacing
shows a free-space zero-elevation gain of about 6.4 dB in one of the two
directions, with a front-to-back ratio of about 10.5 dB.

Which of the three is wrong: Antenna Book, EZ-NEC or me?

BTW: as far as radiation resistance is concerned, EZ-NEC gives about 17.9 ohm at
resonance, against the nearly 21 ohm shown by the Antenna Book.

Tony I0JX

Rome, Italy

EZ-NEC seems not to match the Antenna Book?
 

The graph shows gain (in the two orthogonal directions) as a function of
spacing. For spacing = 0.14 wavelength, the graph shows a bi-directional gain
of about 4 dB (and then a front-to-back ratio of 0 dB).

Unless I did something wrong, on EZ-NEC the same array with 0.14 WL spacing
shows a free-space zero-elevation gain of about 6.4 dB in one of the two
directions, with a front-to-back ratio of about 10.5 dB.

Re-thinking on the results, the gain difference is probably due to the fact that
the ARRL Antenna Book graph gives dBd, whilst EZ-NEC gives dBi.

But what about the great difference in front-to-back?

Tony I0JX

EZ-NEC seems not to match the Antenna Book?
 

Antonio Vernucci wrote:
But what about the great difference in front-to-back?

A later edition of The ARRL Antenna Book shows that
equal bilateral gain occurs at a little over 0.1WL
spacing. EZNEC agrees.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

EZ-NEC seems not to match the Antenna Book?
 

Thanks that's right.
73

Tony I0JX

"Cecil Moore" ha scritto nel messaggio
...
Antonio Vernucci wrote:
But what about the great difference in front-to-back?

A later edition of The ARRL Antenna Book shows that
equal bilateral gain occurs at a little over 0.1WL
spacing. EZNEC agrees.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com