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"The 4 Elephant " Antenna
That's 4 elements - 80 Meters (NO TRAPS NO COILS FULL LENGTH)...
(an overly optimistic number as we found out soon enough)
Additional notes (Fall 2000)by VE6JY
The yagi has been up for since fall of 1998 but not unscathed. The reflector was bent by one of our winter storms at a wind speed much lower than it was designed to handle. It was obvious by looking at it during a wind that any element strength calculation was not valid for such a long and heavy element. The inertia of the element as it swung about created an extra stress which I estimate to be at least equal to the moment caused from wind pressure. Another wind a year later actually straightened out the bend - perfectly! However that didn't really make me feel good as we all know what happens to aluminum that is bent and then bent back.
One other problem was the rotor, or more properly the top bearing. I had used a 6000 pound "implement hub" designed for heavy agricultural loads in a stub axle configuration. Even though it would be subject to large offset forces in my application, I know it would have to carry such weights in it's normal usage. Well, I was quite wrong again as it showed signs of leaning early on. Here you can see Barry VA6DX standing on the sprocket that is bolted to the hub. While nothing had failed to the point of being dangerous, it was time to do it "more right" this time. Getting the yagi in position at the start (1998) had been a full 2 day job using a gin pole and winch - taking it down that way would be not much less work and certainly not fun.
Strengthening the elements was fairly basic with 1 or 2 extra sizes of pipe inserted into the "weak" spots. Even though only the reflector was bent, all elements were reinforced.
The mast was changed to a more conventional system - a 10 cm (4") pipe with 1.2 Cm (.5 inch) wall supported by 2 bearings and hubs (surplus jet aircraft wheels).
Drive power is from a 500 rpm gearhead AC
1/2 horspower motor and so far, appears to have
adequate power to rotate under windy conditions.
Just over 2 minutes is required for a full rotation.
"80-Meters at sunset " Just looking West
"80-Meters at sunset " Just looking West80msunset-b.jpg
The rotor system was reworked and reinstalled on Thursday, September 28, 2000 at about 20:00 hr. UTC.
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