The relationship between antenna length, frequency and wavelength

2021-07-02

Antennas are widely used in the field of communications. Some customers don’t know the relationship between antenna length, frequency and wavelength, and what is the calculation formula for antenna length. Sometimes I see the antennas sold on the Internet with the same frequency are long and short. Doubts, let’s analyze the relationship between antenna length, frequency and wavelength.

The relationship between antenna length, frequency and wavelength

The length of the antenna is inversely proportional to the frequency and directly proportional to the wavelength. The higher the frequency and the shorter the wavelength, the shorter the antenna can be made.

433MHz copper spring antenna SW433-TH32

Antenna length calculation formula

When the length of the antenna is 1/4 of the wavelength, the transmission and reception conversion efficiency of the antenna is the highest. Therefore, the length of the antenna will be determined according to the frequency or wavelength of the transmitted and received signals. Use the following formula to calculate the wavelength, and then divide the calculated wavelength by 4 to get the corresponding optimal antenna length.

The conversion formula of frequency and wavelength is:

  Wavelength=300,000 km/frequency

  =300000000 meters/frequency (the unit obtained is meters))

   For example: The signal frequency used by the wireless data transmission station is 435MHz, and the wavelength is:

  Wavelength = 300,000 kilometers/435MHz

   = 300000000/435000000

   = 300/435

   = 0.69 meters

The corresponding optimal antenna length should be 0.69/4, which is equal to 0.1725 meters.

The above is the relationship between the length of the antenna and the frequency and wavelength. The length of the antenna is directly related to the wavelength of the working frequency. When buying, we may find that the antenna does not seem to be that long. Straighten the inner circle of wire, the length is also close to a quarter of the wavelength.