First of all, we have to say that wifi jammer is very useful in some places where they are needed. The radio frequency band is divided into many discontinuous frequency bands from low frequency to high frequency. Commonly used are the HF frequency band, VHF frequency band, and UHF frequency band. The microwave frequency band with higher frequency is only used for amateur satellite communication and microwave communication experiments. The following are the propagation laws of the commonly used amateur radio bands.
2.80m frequency band (3.50～3.90MHz)
The propagation law of this frequency band is similar to that of the 160m frequency band, and it is mainly based on the mixed propagation of the F layer and the E layer. In summer and daytime, due to the high electron density in the D and E layers, the radio waves below this frequency band will be absorbed and cannot be reflected by the ionosphere. During the day, only a 100-200km distance can be communicated. At the same time, thunder and lightning often occur in summer, so that there is a lot of noise in the frequency band, and weak signals cannot be heard. In the evening or dawn in winter, the effect of long-distance communication is better than that of the 160m frequency band, and the chance of connecting to a long-distance radio station is also greater. The antenna in this band is also relatively large, but it has been much smaller than the antenna in the 160m bands. Besides, there are also many shortened product antennas, which makes it easier to set up an antenna in this band. Generally, it is simple to erect multi-purpose horizontal half-wave dipole antennas. The shortened products are mostly vertical grounded antennas. With a large erection site and sufficient funds, a huge Yagi directional antenna can be erected on an iron tower of tens of meters. !An antenna with a good effect should be set high and long enough.
1.160m frequency band (1.80～2.00MHz)
This is the lowest frequency band allowed for amateur radio stations. The propagation law of this band is very similar to that of medium waves. During the day, ground waves are mainly used for short-distance communication, and at night, long-distance communication can be carried out through the reflection of the ionosphere D layer. The best communication timing is double communication.
Fang is at the junction of sunrise and sunset. In the evening or dawn in winter, it is time to use the 160m band for long-distance communication. Because the frequency of this frequency band is relatively low, a huge antenna needs to be erected, and the ionosphere has a relatively large attenuation to it, and requires a large power to achieve long-distance communication. Therefore, fewer people operate, and CW is used for communication.
4.20m frequency band (14.00～14.350MHz)
This frequency band is the famous DX (long-distance communication) frequency band because this frequency band mainly relies on the F layer of the ionosphere for global communication. The characteristics of this band are that the propagation is relatively stable, the solar activity and seasonal changes have relatively little influence on the propagation, and the ionosphere is open for a long time. In winter, the transmission is slightly worse, and the transmission is mainly opened in Southeast Asia. 
In the spring and autumn, global transmission is opened. In the summer, there is the possibility of DX communication even during the day. Most international competitions and radio expeditions can operate in this frequency band, and most of the radio stations using this frequency band are also for the purpose of DX communication. Therefore, this frequency band is the best frequency band for hunting rare radio stations. The most famous one in China is the China Old Ham Network with a frequency of 14.180MHz. For decades, the Chinese old hams in Southeast Asia gather at this frequency every morning, which is called morning tea gathering. The other is the China Radio Sports Association (CRSA) network on the 14.330MHz frequency. It is controlled by BY1PK at 10:00 am every Tuesday, and informs about the activities of various places and the recent work arrangements of CRSA. In addition to the commonly used CW and USB communication modes, this frequency band can also carry out RTTY and SSTY communication. Antennas in this frequency band can already be made relatively small, and Yagi directional antennas are often used, and the gain of the antenna is relatively high, and many of them use multi-band shared antennas for operation.
The above is a brief introduction to the frequency band division of wifi frequency jammer. If you want to know more about jammers, please continue to read other articles
