decode and send 433 mhz rf signals with arduino

Look this up on google for instructions to do this. I cannot get it to work for several possible reasons. The interrupt code I presume to be 'enable receive(0)'. Waiting for a digital zero to start the interrupt code. When there is no signal from my remote for the mains power switch I am getting voltages ranging from 2.7-3.3 which must be random noise voltages from the data out of my receiver. When pressing the remote button I get a steady 1.8v.
For a 5v power supply a low must be below 1.5v. Therefore the interrupt program can't run.
Another problem I see is the 'output' instruction. Shouldn't this be a 'print' instruction so the results can be seen in the serial monitor? Nothing at all appears on my serial monitor.
Can anybody suggest how I can get this sketch to work?

I don't see any sketch.

Please read and follow the directions in the "How to get the best out of the forum" post.

Type into google search these exact words to get everything you need;
‘decode and send 433mhz rf signals with arduino’
If I had to repeat all that is there, this post would be far to long. My problem with the sketch will be obvious when you look this up on google. I suppose I should have made this reference in the first place. I apologise.

Why do you expect us to do the google? You could have posted the link
url=https://www.google.com/search?q=decode+and+send+433mhz+rf+signals+with+arduino

The first hit (at this moment) is Decoding and Sending 433MHz RF Codes With Arduino and Rc-switch : 9 Steps (with Pictures) - Instructables, the second one Decode and Send 433 MHz RF Signals with Arduino | Random Nerd Tutorials

So now the question is which one of the roughly 31,000 hits you are referring to.

Do remember that those you are asking for help on this forum are volunteers.

So if you have a link to a specific tutorial or code you are using, then it will save the volunteers time if you provide it.