[SOLVED] How to select frequency for this rf receiver?

[saavedra29]

Hello.
I have this receiver that shows 3 frequencies printed on the board: 315MHz, 330MHz and 433MHz. I have also two transmitter modules, a 433MHz and a 315MHz.
The 433MHz tx regardless of the receiver's and transmitter's antenna length is able to communicate. But the 315 not. So why does the receiver write 3 different frequencies? I don't see any "switch" on the module. My father show a trimmer on the board somehow sealed with something like gelatine and told me that maybe i could change the frequency from this. Is he right? And if yes why is it sealed?

 

[FvM]

I presume the devices are produced with one fixed frequency. There should be a respective mark in one of the printed fields. The frequency trimmer is hardly suitable for tuning the frequency over a wide range.

As far as I know, 315 and 330 MHz are no license free bands in your country, by the way. You should also not detune the transmitter, because it's operation might become illegal.

 

[saavedra29]

There is no respective mark on any frequency but when i bought them as pairs (1 TX, 1 RX) they came with their equivalent transmitters. So it accepts only the frequency of the transmitter that it comes with. About my countries laws that's an other story Thank's for the help.

 

[betwixt]

The frequency on most of these modules is decided by the SAW resonator fitted to the board and they are single frequency devices. Someone should have marked which that board was set to. The only way to change frequency is to replace the SAW module. If you look closely on the component side, there is usually a round can although the shape may vary, with some numbers etched into it. You can probably match the numbers with the frequency, for example if it says 'xyz433abc' the number part would indicate the output frequency.

Brian.