This can be used in conjunction with an antenna that can be mounted up high to get better line of site. The receiver itself has a grey wire that is an antenna. However the receiver is not water tight and needs to be kept in a housing. So the grey antenna can be dangled out of the housing but it would be difficult to place it so it achieves better line of site. This is when the coaxial connector comes into play. We have an antenna pre-sized for 318 mhz on the site. It s the LR318 Extended range antenna. The can be purchased and modified for 433 mhz. The length of the antenna at the end of the coaxial cable is what has to be a specific length for each frequency. The 433 antenna should be approximately 6.7 inches long.