This array was been succesfully used from september 2002 up to october 2003, when it has been replaced with the current 4x7 elements system. The set up was very useful for all propagation mode, but the poor front to back ratio was not ideal for EME trafik. With this system I completed seven QSO using both first and second lobes.
Array composed by 4 x 6JXX6 antennas, 7,40
meter long boom yagi
Extimated gain on free space 15.55 dbd (17.7 dbi)
Extimated gain with ground gain 19.5 dbd (21.65 dbi)
Center of the double "H" placed at 17 meter above ground
Horizontal spacing 7,40 meter
Vertical spacing 6,20 meter
First lobe at about 4°, second lobe at about 11° with 1,8 db of
Secondary lobe on E-Plane at -16 db
During optimal conditions, with this array I have been able to
hear my own CW echos running a power of
station was not utilized or when a thunderstorm was approaching (and this happens
very often here in the center of Italy, expecially during summer and autumn) the array was lowered using its coaxial
lift moved by an electric hoist. Just after the
station was set up I was using a manual takle, but I immediatly realized that
lift up an array weighting more than 150 Kg was neither easy nor quick!
"double H" was made by alluminium tubes wich are 2mm in thickness and
60mm inside diameter. For the tube connections I used steel plates with u-bolts.
strong winds blow, the lower antennas was wind-braced at the ground using four
nylon/iron tie-rods. This system has survived without damages at north winds blowing
at over 85 Km/h.
The tx line
was made by 28 meter of 1/2 inch "Ecoflex 15" cable with an extimated
loss of 0,6 db. For the rx line I utilized 28 meter of "RT-50/20"
with an extimated loss of 0.7 db.