Wireless module usage circuit diagram

According to the circuit diagram of the wireless module, when there is no transmission, the DATA output of the receiving module should be at 0 level. However, with the one I bought, when there is no transmission signal, the DATA output of the receiver is messy. 0-5V changing signal. At first I thought the receiving module was bad, but after I replaced it, it was still the same. After turning off all the surrounding electrical appliances and removing interference, only the voltage is stabilized

The power supply and oscilloscope are still the same. But after connecting the transmitting module, as long as the signal (square wave) is transmitted, the receiver will not

There is clutter, and it is a square wave being emitted. After removing the transmitted signal (square wave), about 1-2 seconds later, the receiver has clutter again.
What I do is serial communication between PC and 89C52. Due to the existence of clutter, the microcontroller is always detecting serial port interruptions, which is very annoying. I don’t know what the reason is, can you guys give me some advice? Not grateful! ! !

In fact, I didn't have much hope for this module at first. It's only a small size and has only a few parts. Can it accurately transmit digital signals? Through practice, I feel that the effect is not as bad as imagined. For this module, I think we should pay attention to the following points:
The power supply is very important. Power supplies with large ripples must not be used. This is very important for the reception. The receiving module uses a 78L05 for power supply alone.
Secondly, it must be well isolated from the microcontroller, otherwise it will be affected by the frequency multiplication of the microcontroller's clock and even have no output signal.
There is also the need to connect its antenna. It is best to use a small telescopic antenna.
The preamble is very important. When I use it, the transmitting module is directly connected to RS232 through a level converter to send the signal sent by the computer. The microcontroller receives it. When the preamble is a space (that is, the data bits are all 0 and lasts for 20mM), the effect is Very good, but the effect is not good if the preamble is changed to something else. Logically speaking, a square wave (i.e. 01010...) should work, but the effect after the trial is not very satisfactory. As for the transmission distance, I haven't tested it yet.