An IFF antenna is disposed symmetrically about a vertical axis. A power divider and a pair of transmission lines are provided to symmetrically feed the IFF antenna. A GPS antenna is disposed coaxially of the vertical axis and above the IFF antenna. A gap is provided between the top of the IFF antenna and the bottom of the GPS antenna having a predetermined width. A three wire balun is disposed coaxially of the vertical axis and within the IFF antenna to feed the GPS antenna and a conductive shield is disposed coaxially of the vertical axis surrounding the three wire balun and interconnecting the IFF antenna and the GPS antenna for isolation therebetween.