How to choose a radio frequency wireless module? What are the considerations for radio amateurs in today's society?

How far should the wireless module be able to communicate?

Currently, many amateur radio enthusiasts can communicate over thousands of kilometers with just 5 watts of power. Even using the common 430MHz frequency band for shortwave communication, many amateur radio enthusiasts can use several watts of power to communicate with amateur communication satellites and send images across continents from near ground points to achieve over 1,000 kilometers of communication.

So how far can realistic wireless devices communicate? Take the 430MHz frequency band, which is also known as the line-of-sight frequency band, for example. You can communicate in places where you can see with your eyes. Many radio amateurs around the world use the 430M frequency band to communicate via lunar surface reflection, which can cover half the earth. A better example is the amateur radio station on the International Space Station, and everyone's communication power is not great.

In reality, how far can 1 milliwatt of power transmit? This is easy to test. Connect a radio frequency signal source to an antenna and emit FM signals at frequencies of 75kHz and 5kHz respectively. Use a good amateur radio walkie-talkie in broadband mode and narrowband mode to receive the signals. You will find that the broadband mode is good for less than 100 meters, while the narrowband mode can reach much greater distances.

Bandwidth determines distance because the energy density is not concentrated. Try using 20mW and you will find that narrowband FM communication can reach 20km easily when the antenna is good, while broadband communication is much closer. This is why radio and television stations require such high-power transmitters. Therefore, when there is a requirement for communication distance, the first thing to consider is what communication mode to use.

How much power should the radio frequency wireless module use?

Use a spectrum analyzer and connect it to an antenna. Take a walkie-talkie and move it 5 meters away from the instrument. Press the transmit button and you will see the spectrum of the transmission. Swing the walkie-talkie widely and you will find that the spectrum changes greatly, with changes of over 10 dB. Therefore, if you want to use it while moving, you need to have about 10 times power reserve.

How to extend the communication distance of the radio frequency wireless module?

Networking. Both the area network and the complex small area network can greatly improve the reliability of long-distance communication. Any measures taken, such as increasing transmit power, will not make a qualitative change. Because such chips are not designed for long-distance use.

Long-distance communication mainly depends on the receiver. For the 430M frequency band, at least two intermediate frequencies should be used in conjunction with good filters. For narrowband communications, there are many ready-made crystal and ceramic filters to choose from, while for wideband filters, the selection is not so easy. It can be said that achieving high indicators is very complex and expensive. Filters basically determine the quality of your receiver.