Receiver does not distinguishes between 315 and 434 MHz

[sadpony]

I want to transmit two different data on two different frequencies continuously. I used two transmitters of 434and 315Mhz. But the two receiver receives from both the transmitters. It doesn't differentiates between the two frequencies. Please can any one give a way so that the One receivers from only one frequency while other receives from another. I would appreciate any help that you can give. Thanks in advance.

 

[keith1200rs]

It sounds like you have a very poor quality receiver. I guess the receiver could be overloaded - does it work if you separate the transmitters and receivers by more distance?

Keith

 

[sadpony]

Yes the receiver receives even if the distance from the transmitter is large. I just want to ask, is their any way wherein it is possible to increase the selectivity of a ready made receiver by any additional circuitry. If that is possible then major part of the problem can be solved.
Thanks in advance

 

[keith1200rs]

While I could suggest you add a bandpass filter to the front end of the receiver, you would then be starting to design a discrete receiver which raises the question - what is the receiver actually doing? The function of a receiver is to reject nearby signals and certainly signals more than 100MHz away. So, either you have a terrible receiver or are doing something wrong. Are the transmitter and receiver sharing the same power supply? If so, there could be coupling through the power supply lines and it is not a realistic test.

Keith

 

[biff44]

what chips are you using? Many allow a resonator at the discriminator, or a filter in the gain path, to reject out of band interference. If it were me, I might do FM for one frequency, and AM for the other frequency

 

[jiripolivka]

Most receivers for short-range transmission like car keys, garage openers etc. use simple superregen receivers without any filtering. Pulse code is the only way to make sure only "your" device responds.
The only way to make a better receiver is to make a new superhet receiver (down converter) with the second superregen stage. Then you can use a good filter without losing sensitivity.