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Old July 1st 08, 05:05 PM posted to rec.radio.amateur.antenna
Wimpie[_2_] Wimpie[_2_] is offline
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First recorded activity by RadioBanter: Mar 2008
Posts: 329
Default Optimised antenna

On 1 jul, 14:36, Alan Peake wrote:
Q. What is the optimum antenna type to give the maximum gain given a
fixed overall length of elements? Or, alternately, what's the minimum
amount of wire/tubing to give a specified gain? (Neglecting support
structures)
As an example, for a gain of 15 dBi, an 11 element Yagi appears to have
about the same gain as two stacked 6 element Yagis which collectively
use one more element. But what about collinears, V Beams, arrays of
different sized Yagis etc. etc.?
Just out of curiosity.

Alan


Hello Alan,

There is no optimum antenna design that fits everything. Some factors:
Center Frequency
Side lobe level requirements
Gain requirements
Available materials
Required bandwidth.
Design skills / Experience
Ease of production
Number of antennas to be produced,
Available volume
Sentimental
Environmental aspects
Visibility (think of covert antennas).

There are (physical) limitations on antenna gain and antenna size.
Antennas with high gain must have a size far above wavelength.
Reduction of side lobes with given gain also requires a larger
antenna.

Omni directional gain requires large vertical antenna structures.
Every 3 dB gain increase, requires double the (vertical) size.

Best regards,

Wim
PA3DJS
www.tetech.nl
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