# RF signal receiver is short distance and unstable. Can antenna sovle this? How?

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.

• It sounds like the receiver isn't receiving enough power, the easiest fix is to increase the transmitter power (if you can) or buy a higher gain antenna. Oct 12, 2017 at 3:31
• @jramsay42: I connect receiver to 3.3V. The problem is when I connect it to 5V, a lot of noise will be received. 3.3V almost does not receive noise. Oct 12, 2017 at 3:41

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.