ikalogic said:
well, to make sure, here is an example:
My sender and receiver are in the range 50 to 80 khz
Say i want to give 3 different orders, sending different frequencies from the transmitter, Then, i would use 3 bandpass filters in the receiver to diferentiate between the 3 orders, which are at 3 different frequencies.
am i on the right path??
I wouldn't have said so, not in the 21st century!.
There are many ways to transmit remote control information, certainly using individual frequencies does work - and was used, back in the 1970's, but probably not since then. However, it's crude, complicated, and expensive. Using multiple bandpass filters is a particularly complicated way to do it, it would be better to use NE567 PLL tone detectors instead, they were often used for that purpose.
But far better is to use a modern, simple, cheap solution, and will provide better reliability and more channels than individual frequencies.
Here's a link to a Holtek encoder datasheet **broken link removed**, it's a LOT simpler than trying to use antique methods.
Also, you should be aware that the very low frequencies you mentioned for the RF link will have much less bandwidth than a higher frequency one, and are probably un-licenceable in most countries.
In any project you have to make design choices, is there a particular reason why you decided on such low frequencies, and complicated systems?.