800-meter transmitter circuit diagram using surface acoustic resonator

There are many forms of wireless transmitting circuits using surface acoustic resonators. Here is another circuit. This circuit was made by me after referring to the article in the electronic newspaper 3 years ago and combining it with the actual sample of the module introduced in the article. After mass production, some parameters were improved, and now this product is really good. But now there are too many imitation products of this stuff, and the quality is also very different. But because it is relatively simple, I think it is still necessary to get it out for everyone. I also found many similar circuit diagrams on the Internet, but Some of them have traps. I hope everyone will pay attention and learn to identify some bugs on their own. For this module, I have not tested the absolute power of its wireless transmission, but we drove the car over the distance on the highway. It can reach a distance of 800 meters when combined with the ordinary 315M super regenerative receiving module. Although my circuit As long as the value of the 8050 base resistor is reduced, the communication distance will be increased to 1200 meters or even further. However, a large number of experiments have proved that that is not very reliable. I am not very clear about the reason. There may be two reasons. One It is because the 8050 conducts slightly when R2 is small, causing the emission to not be cut off quickly. Another reason is that R2 is very small, and the opening current of 8050 is relatively large, which may cause a disturbance to the power supply and fail to meet the oscillation requirements. I once doubted whether my circuit was a good match, so I bought a lot of similar modules that claimed to be 1500 meters long, and found that they also had the same unreliability. The common manifestations were that they occasionally failed to oscillate or the baud rate was less than 2K. Later, I added the R2 resistor. When it is greater than 15K, the emission has been normal, and the distance is about the same as that of 27K, so I use this resistor now. For L1L2 here, I use 0.8mm enameled wire without enameled wire and a 3mm drill bit. It is formed by winding 4 times and half.