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How to reduce the length of antenna ?????

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ZengLei

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For example :there is a small radio station ,and its frequence is 30MHZ,if we use the antennas with 1/4λ,so the length of the antenna is 2.5M,and it's not very convenient to carry,and i want to reduce the length of the atenna without reduce the power the antenna transferred,any idears?????

Thanks~~~~~~~~~~
 

soliquid

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hmmm........modulate the signal
 

jallem

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There techniques for miniaturization of antennas
while keep it resonant.
 

Rf engineer

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u may increase the frequency...it automatically reduces the length....secondly try to make it resonant...but y r u keeping the length smaller...
half wave antyenna is much more than 90% effective radiator.
 

ZengLei

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maher mohamed ::
and~~
i mean that how to reduce the length of the antenna ,with a frequence~~~~~~,
for eaxmple: the frequence of the carrier is 315MHZ,so the length of the antenna may be 1/4λ=23cm,so i want to reduce the length and still use the carrier of 315MHZ~~~~~

THANKS
 

cyberrat

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If you want to reduce the length just for carrying, do you want to be able to use the antenna while you carry it?

because if not you can simply cut it in half & stick it back together (like a fishing rod) when you have done.

Or you can start messing about winding a coil at the bottom to enable you to shorten it but it will lose power, a shorter antenna will not be as efficient as one that is the correct size.

You can make it 1/8 wave.

Are you wanting to use 30 or 315mhz?
 

mateuko

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You can use shorter antenna and make it "electrically longer" by connecting in series an inductor. Have you ever seen car CB radio antenna? It has a few turns on its base and is greatly shorter than
antenna mounted on the roof of CBst house.
 

Mansour_M

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Hi Every One!

To reduce an antenna size we can use dielectrics with high permittivities. Because existance of permittivity will reduce the wavelength, then the final antanna size is shorter. An examle of useage of this method is a Dielectric Resonance Antenna.

Thanks!
 

nikhilele

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You can use Helix or Helical antenna this can do your work.... with conditions apply.
 

jallem

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There are several techniques for reducing size:
1) Inductive loading: is using a inductance in the
point of lower potential or highest current, as some
one said, for ex: in the base of the monopole.
2) Capacitive loading: the opossite concept.
3) meandering: making the antenna lenght equivalent by bend it or folding it.
4) fractals: is another method, is equivalent to
meandering.
5) harmonic tuning antenna: is when the antenna
is tuned to lambda/4 or lambda/8, etc.

All of the method can keep the antenna resonant
while being smaller but there is a price to pay, the
effective area is reduced so is the efficiency of the
antenna.
 

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