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# How to determine the length of the antenna?

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#### eugenehhk

##### Member level 1
calculate antenna length

Hi all ! I am a student, I have a project need me to use RF TX and RX modulus to transmit the data. I would like to ask how to determine the length of the antenna and how to calculate the output power of the signal. (if the RF TX is 433.92MHz and modulate mode is ASK.)
THX

#### boy

calculating antenna length

This migh help

### eugenehhk

Points: 2

#### sinip

##### Full Member level 4
how to calculate antenna length

eugenehhk said:
Hi all ! I am a student, I have a project need me to use RF TX and RX modulus to transmit the data. I would like to ask how to determine the length of the antenna and how to calculate the output power of the signal. (if the RF TX is 433.92MHz and modulate mode is ASK.)
THX
You can find many programs on the net for calculation of antennas. For that frequency you can use dipol, yagi, quad, helical or many other designs. Just decide about what antena you need and search for computer program that does the calculation.
Output power depends upon what you have in power output stage. Datasheets are usually readily available on the net.

### eugenehhk

Points: 2

#### rigdoctor99

##### Member level 1
how to determine antenna length

To calculate the wave-length devide the speed of light by the frequency in Hz. Or simplified, 300/freq.mhz=wave-length in meters.......

#### nycheung

##### Newbie level 6
calculate antenna size

For 433MHz, wavelength = 693mm

assuming you are using dipole antenna, it should be wavelength/2 (346.5mm) each side from the feed point.

Good Luck!!

### eugenehhk

Points: 2

#### sinip

##### Full Member level 4
determining antenna length

nycheung said:
For 433MHz, wavelength = 693mm

assuming you are using dipole antenna, it should be wavelength/2 (346.5mm) each side from the feed point.

Good Luck!!
You should take into consideration so called "shortening factor". Sorry but I don't know if it is called like that in English. It is some multiplier that you have to multiply calculated dimensions to get the real physical one. For plain wire it is something like 0.95, for coaxial cable is something like 0.66 if I remember well. Not that it matters much at high frequencies though...

Points: 2