TL;DR: How would one send a fixed radio signal at 447,54MHz with Arduino?

Background: I recently purchased a (receive only) SDR and recorded my garage door fob. I found it sends a fixed signal at the frequency 447,54MHz, which I was able to decode. Now I want to try activating the garage door via Arduino. The standard 433MHz senders obviously don't work, since they have a totally different frequency.

I tried searching for senders of my frequency (447MHz) and also for senders with different or variable frequencies. I didn't really find much. Also I read in some post (that I don't remember currently), that building an own sender circuit is not easy (since the exact PCB design plays a big role in the behavior in the ciruit). It didn't seem, that this would be a valid way for me.

Has someone here experience with such frequencies? While I know, that this site doesn't do product recommendations, maybe I just searched for the wrong term and you can help me with that. Or maybe there are no (or very very few) "maker-ready" products for this out there currently. Maybe the creator of the garage door system wanted a non-standard frequency for security-through-obscurity (since that doesn't protect against attackers with a sending SDR).

Also I researched about frequency bands. Normally I would think of a garage door fob as a Short Range Device (SRD), but instead my frequency is right above (and outside) of the band PMR. Maybe this is because the system is really old (can easily be between 15 and 30 years).

I'm kinda lost on how to proceed here, or if proceeding is even viable here.

  • you have to find a 447,54 MHz transmitter that has a digital input pin ... your question is not about Arduino, so you are limiting your success by posting here – jsotola Mar 17 at 21:14
  • Did you try tuning the standard 433 MHz receiver, adjusting the coil parameters for your secret frequency and don't share your frequency someone can jam your signal or listen to incoming data! – Avon97 Mar 18 at 1:06
  • @Avon97 Is it possible to detune a standard 433MHz sender with different coils to a frequency so far away from 433MHz? The sender modules that I have don't even have a coil on them, though I know, that many others that you can buy have (a fixed) one. I shared the frequency, because it is integral to the question. And its really security through obscurity. If someone would really want to jam my signal, he could just record your fobs signal with an SDR (for example, when we go out for work) to get the frequency. Just as I did. – chrisl Mar 18 at 7:27
  • 447 MHz is not realy a problem to build. The little chinese 433 MHz T/R module pairs prove that. ;-) But there are legal issues you could run into outside of a public band. Here is an example: cdt21.com/wp/wp-content/uploads/support/download/docs/… Search for PLL Synthesizer (Modules|Chips) for 447 MHz to find more. – Peter Paul Kiefer Mar 18 at 11:49
  • Try to receive a 433 MHz device (a car key or something) on your SDR just to double check your setup. – Wirewrap Mar 19 at 19:40

The standard 433MHz senders obviously don't work, since they have a totally different frequency.

I think "433 MHz" is used as a band name, with 433 MHz actually being at the lower limit of a band that covers approximately 40 MHz. Your garage door opener will likely be referred to as a "433 MHz garage door opener", even though it operates at 447.54 MHz.

For your experiments, you might try the HC-12 module. It's billed as a 433 MHz radio, but in fact it covers 433 MHz to 473 MHz in 100 bands with 400 kHz spacing, so it will cover your desired 447.54 MHz. The link above has some Arduino code examples that might help get you started. And of course there is much more information on this topic if you're interested.

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