Hi, I am using 3 modules receivers of 433Mhz with a remote control (pictures below). They are connected to 5V and an esp32. Right now it receives a signal from about 30 meters, when I used only one module it worked good for 50+ meters with no issues(guess it could do more).
What is the correct and best way to optimize the receiving distance with the antennas it came with? I am putting in a small box, do they have to be straight and out of it?
Any recommendations for other better flexible antennas?
I also have this receiver, and connected a coil shaped antenna to it, but the results were very poor. Is it because of the module or again not soldering or using it correctly?
There is no correct or best method really, but the choices for optimising an antenna for reception range are limited, especially if the module used does not provide an RSSI output.
You will probably be limited to testing on a large open field, somehow make the receiver beep or flash a light when it receives signals from the transmitter and walk away for the receiver until reception stops.
Make changes to the antenna, length, orientation etc, and see what gives you the best distance.
Those coiled antennas will almost always be worse than a straight bit of wire of optimum length.
And whilst you can supposedly calculate the length of the antenna that assumes the receiver device has an antenna input impedance of circa 50ohm. In practice, most cheap RF devices are made of cheap components which vary in value so you often wont get an exact input impedance. Then of course the length for maximum received signal will be different from the classic calculated value.
When you ask about receive antenna optimization, you are beginning a never ending search. Begin by using Google to search for "antenna 433mhz". Look at the images and see if some interest you.
For distance, the antenna at the sender and at the receiver might be best if they are similar. Antennas between devices work best if the antenna is directional and pointed at each other. The antennas that come with the cheap devices are all omnidirectional. Meaning they transmit and receive from ALL directions, equally poorly.
Antenna building at the frequency you are using is quite easy to do. Try some different designs at the ends and see what is optimum for you.
properly, your question should end with "in ( regulatory domain )", because the law factors in
in reality, if you are in the FCC regulatory domain you would have to do something seriously weird to get bothered by the FCC. the rules here are:
the device is certified as a package, including the antenna. the manufactuer designs and calibrates the intentional radiator in a way that produces max legal power with the joke of an antenna they provide.
you can legally use a maximum 8db omni antenna. no directional antennas are permitted
in reality, in reality you there is very little chance that you would interfere with anyone who could figure out who you are and drop a dime.
Thanks all for the responses, I will try the things you said.
Something that I found is that the remote control when held up to the sky and not towards the receiver device functioned better(when they are both on the ground).
