Bob2. Retired Nuclear Instrumentation System Engineer (formerly with Exelon Quad Cities Nuclear Power Station and TVA Browns Ferry).
Top picture is the primary VHF/UHF tower. 80' stationary with 50' K0XG rotating top. Pairs of long boom 6M through 3456 MHz antennas. 6M antennas are on 50' booms at 105' and 130'. The main lobe for the pair has about 15dbd (free space gain) at a 2 degree arrival angle. The 2M ants are on 32' booms and are at 140' and 154'.
The 4 Bay 6M Array completed May of 2013. 8x7el. Each bay has 2 antennas stacked at 1/2WL (~10' - close spaced to suppress noisy high angle vertical lobes rather than produce maximum stacking gain). Each bay is "hard phased" with a 3/4 WL power divider of 75 ohm coax. The pair emulates the gain of a longer boom antenna with ~13dbd free space gain, but has a much broader AZ pattern.
The bottom bay is at 1WL above ground (for high angle), then 1.5WL spacing (20, 50, 80, 110 feet to the center of each bay). The 4 bays are selectable in any combination to take advantage of different wave arrival angles from 2.5 to about 25 degrees. Total gain with all bays selected is about 19dbd (free space) at a 3.5 degree radiation angle, however this does not tell the real story. During Es and other propagation modes with varying arrival angles, switching the arrival angle can increase received signal by 20 db or more. This array often opens the band first and closes it last; and is very effective for ionoscatter out past 1000 miles on an otherwise "dead" band.
Top of the 160' K0XG Rotating Tower showing the top bay of the 6M array but with the June 2014 addition of a KT-34XA 6el Tribander and a HyGain Explorer Shorty 40. Both antennas were in the garage for almost 20 years and put up for the ARRL Centennial QSO Party to operate as W1AW/9 from Illinois. A homebrew 4 EL 10M at 35 feet is not shown.
The horizon from the lower 11el 6M antenna's perspective at 105'. 6M array is to the right. Looks pretty much the same 360 degrees around.
1974575 Last modified: 2015-05-18 20:19:27, 3793 bytes
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