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I bought two RF modules that were made by different manufacturers. They were both labeled 315MHz on the manufacturers' websites. However, when I tested their frequencies with SDR#, I saw that even though they both fell into the 315MHz range, their frequencies aren't exactly the same.

Will the two RF modules be able to communicate with each other?

Please kindly refer to the screenshot below for the tested frequencies:

enter image description here

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    $\begingroup$ Hello, and welcome to ham.stackexchange.com! I take it that the signals from the two modules are the two vertical lines in the orange horizontal bars. How far apart are they in frequency roughly, about 100 kHz? Are your modules tunable? What kind of modulation were you thinking of using? Sorry to be ignorant, but what do you mean by "module"---is that an oscillator and an amplifier combination? Please edit your question to provide more information, including the general idea of what you're trying to design. $\endgroup$
    – rclocher3 ♦
    Dec 30 '17 at 17:06
  • $\begingroup$ I'm not sure if you should send on 315 MHz if that's a military air frequency. (Might be different in your country) $\endgroup$
    – Thomas Weller
    Dec 30 '17 at 22:32
  • $\begingroup$ @ThomasWeller I noticed that too, but when I Googled 315 MHz band, what he is doing seems perfectly legal in more than one country. $\endgroup$
    – Mike Waters ♦
    Dec 30 '17 at 22:54
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It is difficult to give a specific answer based on the limited information supplied. Here are some general considerations:

  1. Most receivers will have a tolerance for locking onto a transmitter's frequency. The specific tolerance is fully dependent on the design that has been implemented by the manufacturer. But consider that even with modules supplied by the same manufacturer, there will be a tolerance associated with the transmit frequency for which the receiver must adjust accordingly.
  2. There is more to consider than simply frequency tolerance when mixing modules from different manufacturers. The modulation mode, the modulation index, the encoding methods, etc. must be matched between the receiver and the transmitter. For example, if the transmitter is sending with amplitude modulation (AM) and the receiver is decoding signals using frequency modulation (FM), even if they are on the same frequency, the two will not be compatible.
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