In the past I used a remote for a AIWA Hi-Fi to control a AVR processor and circuit I custom made. I used an infrared receiver from Vishay (tuned on the 38 kHz) to demodulate the signal, then fed to the AVR (custom board, not Arduino).
The remote I have uses NEC protocol (http://www.vishay.com/docs/80071/dataform.pdf and https://techdocs.altium.com/display/FPGA/NEC+Infrared+Transmission+Protocol) that is based on pulse distance encoding.
The circuit controls fluorescent lighting (selection of lamp and intensity) in the living room and I found that it has some problems with interferences from the fluorescent tubes. The software already discards most of them but I'd like to improve it.
I would like to use the same remote (due to the multiple and nice looking buttons) but retrofit it with a 433 MHz transmitter.
Would one of the cheap 433 MHz emitters accept the signal meant for the IR LED, after a proper low-pass filter to remove the 38 kHz modulation? or would the 38 kHz modulated signal already work with the transmitter?
On the receiving side I have more freedom and I can put a demodulation circuit if needed, only the remote is space and electronics constrained, that is why I would like the simplest possible solution for the transmitter.
Edit
Clarified protocol and encoding
Best Answer
Yes there's a good chance that the 38 kHz modulation works directly with a 433 MHz transmit module. It so happens that both IR and 433 MHz use the same OOK modulation at 38 kHz. So I would say that it would not work if you removed the 38 kHz signal !
A simple receiver module (BTW get one with an AGC on it like this one) will get rid of the 38 kHz for you, the same as that the IR receiver (which is currently in your AVR processor) will do.
I think you can just replace both transmitter and receiver and it should just work. No additional filter is needed.