Navigation, identification, and collision avoidance antenna systems

An antenna to operate about a center wavelength and in association with a ground plane, comprising:

• first and second monopoles that are spaced apart above said ground plane wherein each of said first and second monopoles includes:
• a feed post;
• a shorted post spaced from said feed post, coupled to said ground plane, and having a length less than one fourth of said center wavelength;
• and
• a top load coupled to said feed post and said shorted post and configured along orthogonal minor and major axes of said top load to have a width along said minor axis and a length along said major axis that exceeds said width;
• and wherein:
• said first and second monopoles are spaced apart along a monopole axis of said antenna;
• and
• said major axis is rotated from said monopole axis by a rotation angle between 40 and 50 degrees.

An antenna system to operate about a center wavelength, comprising:

• first and second antennas each formed with a ground plane and first and second monopoles that each includes:
• a feed post;
• a shorted post spaced from said feed post, coupled to said ground plane, and having a length less than one fourth of said center wavelength;
• and
• a top load coupled to said feed post and said shorted post and configured along orthogonal minor and major axes of said top load to have a width along said minor axis and a length along said major axis that exceeds said width;
• wherein said first and second monopoles are spaced apart along a monopole axis of their respective antenna and the major axis of each of said first and second top loads is rotated from said monopole axis by a rotation angle between 40 and 50 degrees;
• and wherein said first and second antennas are arranged with the ground plane of one facing the ground plane of the other and the monopole axis of one substantially orthogonal to the monopole axis of the other.