Monthly Archives: November 2016

Cheap 433MHz Transmitters

Due to WordPress’s abysmal handling of code blocks this blog post is now hosted at

I decided the other day that it would be a good idea to spend 99p on a 433MHz transmitter and receiver pair from eBay. Not to use, but to take a look and see just how bad these modules are (and I expected them to be pretty awful too).


These modules are the absolute bare minimum you can get away with for transmitting data. There isn’t actually any modulation as such, the data pin on the transmitter (which is the smaller of the two modules) just turns the carrier frequency on and off. This is called On Off Keying, or OOK (No, not Ook, Ook! or Ook?, but OOK). The receiver just tells you if it can “hear” that carrier frequency.  There’s no data protocol, no packets, no nothing. You just tickle one end and the other end giggles.

They’re great for sending UART data across the air waves. Connect the transmitter to the TX pin of one Arduino and the receiver to the RX pin of another and you can send data between them pretty simply.

Sounds great, yes? Well, actually no, not really. Let’s take a look why. Continue reading