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write your own review of the Universal HD 21-70.
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K8FFO
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Rating: 4/5
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Nov 7, 2009 06:12
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Strong
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Time owned: 0 to 3 months
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I bought mine used and immediately replaced the 14" top section with an 18" top section for added strength. Assembled everything on the ground, including rotor, 8 element LP antenna, 2 meter beam, six meter beam, VHF vertical on top, inverted V antenna and sidearm for my weather station. Universal recommends that everything be assembled on the ground and then walk the tower up. Walking the tower up was impossible as the total weight with everything on the tower was over 600 pounds. Raised it all with a crane without a hitch. This tower is VERY strong and easy to climb (if necessary).
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AA8LL
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Rating: 4/5
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Jul 29, 2007 04:44
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we modified it
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Time owned: more than 12 months
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My tower was originally purchased as an HD21-70
Three of us were able to walk up the bottom four sections. My yard was too small to stand up more than that. The top three were put up with a gin pole. I had a Mosley Pro67B and a Force 12 80-meter rotatable dipole on it on a 10 ft HD Steel mast. I was not happy with the top (14") section as it seemed too light and I weigh 250 lbs. The tower was up for about 10-months and went through the winter OK but in March 1996 we had a big storm. The wind twisted off the top tower section just below the rotor plate. It was ugly. I don't know how strong the winds were but utility poles were blown over about a block away.
My homeowner's insurance would pay for the repairs but my friends KC8MK and K8XU suggested we redesign the top of the tower to help absorb the rotational loads. We replaced the top two sections of the tower with two 18" straight sections. We put an 18" rotor plate at the top with a thrust bearing. We put a second 18" rotor plate about 2' down in the second (from the top) 18" section. We got a 20' aluminum mast with a .5" thick wall (very expensive). Now the rotational loads were cushioned by the rotational flex of the big aluminum mast in the second section and the bending loads were in the top section. I don't know if our engineering is correct but the tower never broke again. Universal says it's "not necessary."
A few years ago we moved and the "powers that be" decided 40' was all the tower we could have. It's another long story and not relevant here. We now have the four bottom sections only up. I had to fabricate 2 rotor plates for the 26" now top section. Universal didn't offer a 26" rotor plate and wouldn't consider making one special for me. This short configuration looks bullet proof. The Mosley doesn't play quite as well at 40' as it did at 70' but it sure is easy to work on with a tow-behind man lifter from the rental yard.
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