Problem with RF transmitter/receiver module
I am using RF transmitter/receiver module (315 MHz) to operate a relay. The transmitter uses an encoder chip SC2262 and the receiver is constructed around decoder chip SC2272. The recommended resistor value for encoder is 4.7M & 820K for decoder respectively.
The problem is that the circuit works fine within 10 feet range but when I move transmitter farther, the rely do not operate. Upon checking with oscilloscope, I found that the digital signal frame is still receiving at the receiver module with same amplitude & without any interference, so can anybody help me why the receiver is working within short range while the same signal is receiving with far distance?
Data-sheet is attached
Are you sure that the DC level of the received signal is not changing at the decoder input?
Frank
Both signal are compared (with short distance where the relay operate & with long distance where signals are received but relay does not operate) they are with same amplitude at the decoder input without any noise. The receiver sensitivity is -108dbm.
There might be a multipath fading between transmitter and receiver.If there are some objects that reflect the signal with a time delay that is very difficult to observe with an oscilloscope, it may create a perturbation on received signal.
Just an idea...
BigBoss, I think there might be a fading problem which difficult to observe with an oscilloscope, due to this reason receiver do not operates the relay. So, what is solution to fix this problem? this type of commonly available rf module work around 50 meter satisfactorily but in my case range is 3 meters only.
If it is fading problem, it should work again if receiver moved further away. This problem may be due slightly mistuned receiver. You can try by rotating slug in coil on either side not more than 5-10 degree. Did you put antenna wire on both receiver and transmitter. A hookup wire of around 18 inch works satisfactory. You can get 100ft reliable range if setup correctly.
What type of antenna do you use ? Use antenna polarization e.g. horizantal or vertical.Or, code your data to recover at RX side..
I am thankful to all.
Dear BigBoss, these type module usually requires 23cm wire as antenna (both in transmitter/receiver) as 1/4 wavelength, however 1/8 or 1/16 lengths also used in many application & works satisfactory with slight difference in the range.
Dear ALERTLINKS, these modules are pre-tuned, so i think that opinion of Mr.BigBoss has argument to accept it. But how to fix the problem?