is it necessarry to modulate the signal cann't we send it as ASK or OOK
signal
With a modulated signal (typically around 40 KHz) from the sender and a
bandpass filter for the same modulation frequency on the receiver then
you can be relatively immune from spurious signals, particularly big DC
signals like sunlight or even incandescent bulbs.
An outgoing signal is easy to modulate. On the receiver side, you'll
have to run the numbers to see whether it's more cost effective to spend
non-recurring engineering costs in designing your own receiver or to
just buy a canned module.
If it's for self/class/curiousity, then a build-it-yourself would be a
fun project. If for a commercial product, much harder to justify. There
may also be patent issues involved in a new design where, presumably,
royalties and rights for commercial use would already be part of the
price of an off-the-shelf unit.
