I am using a 315MHz RF receiver and transmitter pair, which are connected with Arduino UNO board. The objective is to copy 315MHz RF signal, and replay it back. FYI, the design is very similar with this.
The overall design works already. But, the problem is: the RF receiver must very close to RF signal source when copying (e.g. less than 10cm).
When the distance is more than 15cm, the copied signal is always unstable (e.g. the value of LOW and HIGH vary). When the distance is more than 25cm, the receiver always cannot receive the signal.
How to solve this? Can this solve by software? Maybe add antenna? I do not have such knowledge about antenna.
Best Answer
Yes!
Yesterday I started with my 433 MHz wireless transmitter and I noticed as well that it only worked within 10 cm. Then I looked around on the interwebz to find a solution, just like you, and I found out that adding an antenna with a length equal to a quarter of the wavelength makes wonders. So now it works for a couple of meters.
So you need to hook up two wires that is roughly \$\frac{c}{4f}=\frac{3×10^6}{4×315×10^6}=23.8\$ cm long. One for the sender and one for the receiver.
The antenna will radiate in a donut shape around the wire. So the orientation of the antenna makes a huge difference.