I. Location Selection:

1、When used over long distances, the difference in altitude between the two antennas must exceed the curvature of the earth, which is also known as the Fresnel zone.

Fresnel zone influence: Under line-of-sight conditions, the wireless signal travels in a straight line without obstruction between the transmitting end and the receiving end. This requires that there be no objects that block the radio wave within the first Fresnel zone. If the conditions are not met, the signal strength will significantly decrease. The size of the Fresnel zone depends on the frequency of the radio wave and the distance between the transmitting and receiving devices. To ensure normal system communication, the height of the transmitting and receiving antennas should be set so that the obstacles between them are kept within 20% of the Fresnel zone. Otherwise, multipath propagation of electromagnetic waves will have adverse effects, resulting in a decline in communication quality or even communication interruption.

As shown in Figure 1, the 4G frequency reference can quickly determine the appropriate height for the site.

2、When using at a long distance, the Fresnel radius issue needs to be taken into consideration:

As shown in the above figure, points A and B represent the antenna positions at the transmitting and receiving ends respectively. D represents the test distance. Within an ellipsoid centered on the "line" connecting A and B and with a radius of r, there should be no obstruction from mountains or large buildings. r is the Fresnel radius.

Additionally, the microwave equipment operates in the 1.4GHz frequency band. To prevent possible interference from other wireless signals and ensure the accuracy of the distance measurement, it is recommended that the test points A and B be located within a few dozen meters without any visible antenna towers or high-voltage power lines.