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why antenna is of quarter wavelength

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bizoo

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can any one tel me why the antenna for transceivers works optimum if its is size is of quarter wavelenght? wats so special is at quarter wavelength?
 

Maximum power transfer.

Quarter wave one direction....reflects back another quarter wave= 180 degrees

combines witth the incoming wave....therefore it cancels. All the energy is transmitted.
 

I think it probably evolved from a 1/2 wave horizontal dipole which has an approximate impedance of 75 ohms. 1/2 wave is chosen since it presents a reasonable real impedance at the feed point. Replace one half of the dipole with a ground plane and you have a 1/4 wave length antenna fed against a ground plane with an approximate impedance of 37 ohms.

Actually, a 5/8 wave length vertical is the best length because the major lobe of radiation is the lowest angle to the horizon, hence you get the longest distance. However, it needs a matching network to transform the feed impedance to something common like 50 ohms.
 

At the length half lambda, the antenna resonates. The antenna reaches
a maximal radiation resistance, so the antenna works optimal.

If you bring the antenna above a metallic plate of 'infinite' extent, you
can save the length to the half

regards
 

yendori

Maximum power transfer.

Quarter wave one direction....reflects back another quarter wave= 180 degrees

combines witth the incoming wave....therefore it cancels. All the energy is transmitted.


hai yendori ,


i am unable to visualize it.. could u plz explain it some aids
 

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