Description of the old array 4x6 elements


 

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 degradation

        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 85 watts.

When the 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!

The "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.

When 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 antennas were coupled by a power divisor provided by Labelitaly.

At the top of the tower was placed a watertight box containing the SP-6 preamplifier and the HF-400 coax relay.

 

 

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.

The rotor was provided by Prosistel. The model was the PST-2051 with a modified clamp to avoid any rotation of the mast.

 

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