X7 Tribander by Cushcraft
Cushcraft X7 antenna design is based on Log periodic-Yagi and has real advantage over conventional multiband trapped tribanders. Core of X7 antenna is 4 element log-periodic driven cell. Parasitic reflectors for 20/15m and trapped director for 20/15/10m complete this antenna into great compromise on 18' boom.
Advantage of it's Log periodic cell over full size dipole (in free space) is 0.45 dBD on 20m, 1.93 dBD on 15m and 2.57 dBD on 10m as modeled by EZNEC. Aside gain, cell has added another great characteristic to this antenna which is low VSWR on all three bands.
Shown bellow is the driven Log-cell of X7 antennas as well as gain graph of cell itself.
Shown bellow are Azimuth radiation patterns in free space for 10/15/20 meters as well as for 12/17 meters. Antenna is designed primarily for 10/15/20 m but shows a good performances on WARC bands.
10m AZ pattern
15m AZ pattern
20m AZ pattern
12m AZ pattern
17m AZ pattern