I built a simple one-way RF communication system, using a couple of cheap 433 MHz transimtter/receiver modules. Some experienced people told me to change them because they're worth nothing, and so will I do. But I'll not be able to purchase new modules in the next couple of months, so I would like to improve the existing system to be able to continue working on my project.
I need the rf signal to be as strong as possible, because the receiver is in a noisy environment (surrounded by small and fast-spinning brushed motors without terminal-case capacitor). At this very moment the transimtter module is connected to a straight single-core insulated copper wire quarter-wave lenght antenna and is powered by a 9V battery; the receiver has a symilar antenna and is powered at 3.7V (I can't change this voltage).
I transmit 48-72 bits data packets. The transmitter generates a 433 MHz signal during x microseconds if the bit is 1 and nothing (for the same time) if it is 0, where x can be any value (I set it to 1000, but it can be higher (or lower)). I'll always transmit within less than 4-6 meters, and I don't need the transmission to be 100% reliable (even if, say, a packet every two gets lost it would not be a problem... but the other 50% must reach the receiver!)