In the wireless bridge video transmission system, the transmission distance of the wireless bridge has a great relationship with the transmission power and frequency of the wireless bridge and the antenna gain. The following is some knowledge of Feng Runda finishing to introduce the relationship between wireless bridge transmission distance, transmitting power, receiving sensitivity and frequency:
[Lfs](dB)=32.44+20lgd(km)+20lgf(MHz), Lfs is the transmission loss, d is the transmission distance, and the unit of frequency is calculated in MHz.
It can be seen from the above equation that the propagation loss (also called attenuation) in the free space is only related to the working frequency f and the propagation distance d. When f or d is doubled, the loss will increase by 6 dB.
Wireless bridges transmit in the air in the form of electromagnetic waves, which are lossy during transmission. The following formula illustrates the loss of radio waves in free space:
Los = 32.44 + 20lg d(Km) + 20lg f(MHz). Los is the propagation loss in dB; d is the distance in Km; f is the operating frequency in MHz.
The following example illustrates the propagation distance of a system in free space with a working frequency of 433.92 MHz, a transmission power of +10 dBm (10 mW) and a receiving sensitivity of -105 dBm:
1. Transmit power +10dBm, receiving sensitivity -105dBm, Los = 115dB.
2, calculated by Los, f d = 30 km.
This is the ideal transmission distance. The actual application will be lower than this value. This is because the wireless communication is affected by various external factors, such as the loss caused by atmosphere, obstacles, multipath, etc. The reference value is included in the above equation, and the approximate communication distance can be calculated.
Assuming that the loss caused by the atmosphere, shielding, etc. is 25 dB, the communication distance can be calculated as: d = 1.7 km.
Conclusion: For every 6 dB increase in wireless transmission loss, the transmission distance is reduced by a factor of two.
It can be seen that some of the most important factors affecting the transmission distance of a wireless bridge are: transmission power, antenna gain, operating frequency, and whether the site environment is blocked or not. Therefore, it is important to understand the situation on the site before setting up the plan. Otherwise, the plan may be very different.
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