Are you looking for a tiny "rubber ducky" for 433 MHz to put on a PC board? This type antenna has poor efficiency and gain but they are useful if both ends of a link are nearby, like a car and its paired keyless entry keyfob. It is also known as a radial mode helical antenna, as opposed to the axial mode helical antenna which is much larger, is more efficient and has much better efficiency. Your best bet if youre looking for the small keyless entry antenna would be to buy one from ebay or Amazon.
There is a simple nomogram for this design at
http://www.qsl.net/aa1ll/helical2.jpg .
A higher gain antenna will give better pre-detection signal to noise ratio when the received noise is internally limited, i.e., when external noise (atmospheric, galactic, man-made, etc.) is much less than noise generated by stages internal to the radio (LNA, mixer, filter, etc.). Higher SNR will normally result in longer range for a data link. So, yes, when the received noise is due mostly to the internal stages of the radio, a higher gain antenna will increase range. For example, if there is lots of man-made noise around, this will not be true since the antenna is receiving both signal and noise.
--2N5109
