If i have a 4 layered PCB can i use 1 of the inner layers as the Spiral antenna? Or that would produce too much interfearace?
You could, but you’d probably lose a bit of performance due to the need to penetrate the FR4*. A hidden antenna should work just fine.
*This is, of course, that you don’t have any components or copper on any other layer that would be adjacent to the antenna. If you have one spare layer and are trying to cram an antenna on it you’re only going to have problems if it works at all. I don’t know your RF background, though, and mine’s pretty slim too.
look at the chip antennas - many vendors. Size of the nail on your little finger. Widely used in bluetooth devices. Some WiFi too.
Tnx allot Stevech, i didn’t know about these antennas, Really appriciate the info.
here’s a distributor for one manufacturer’s antenna. There are many chip antenna manufacturers, mostly in Asia.
I use ZigBee products with Chip Antennas, e.g., MaxStream XBee.
Yep, that’s the one i had in mind. 
Tnx again for all the info on this, i really appriciate this.