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Reviews Categories | Towers, masts, accessories, climbing gear | Universal HD 21-70 Help


Reviews Summary for Universal HD 21-70
Reviews: 4 Average rating: 4.3/5 MSRP: $(missing—add MSRP)
Description: Freestanding Aluminum Tower
Product is in production.
More info: http://www.universaltowers.com/pdf/HD_models/09-model%23-hd-21-70.pdf
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AB7FS Rating: 5/5 Nov 10, 2011 09:07 Send this review to a friend
Sturdy tower  Time owned: more than 12 months
Summary - a sturdy tower capable of carrying a lot of antennas and surviving high winds. I am more than pleased with mine!

I put up my HD21-70 ten years ago section by section using a gin pole -- although the manufacturer recommends erecting on the ground and walking it up -- it is clearly impractical with such a tall tower -- we were able to walk up three sections - 30 feet - and that was tough going LOL.

The tower carries a KLM 205 - 5 element monobander at 70 feet (12 sq ft), a Tennadyne T7 Log Periodic (6 sq ft) on a mast at 79 feet and a Comet G3 at 80 feet and supports an OCF dipole with a DX Engineering balun at 68 feet. With antenna switches, the balun and support, the mast, tower lights and coax the total wind load is at 21 square feet. The tower is rated to 70mph with 21 square feet.

Initially I had the rotator mounted 15 feet down inside the tower to rotate from the sturdier 18" tower section as the 10' top section (14") is of a very light construction. The mast is 2" thick wall (1/4") aluminum.

Couple of winters back we had sustained high winds of over 60 mph with gusts to 84 mph. To my amazment the tower survived - but the rotator was totally trashed - that was what saved the tower! The antennas weathervaned and eliminated the rotational forces on the tower.

I replaced the rotator and installed it on a homemade plate 3 feet off the ground and now drive the antennas with a 70 foot "torque tube" - a 2 inch drive line made of thin wall irrigation pipe. This soaks up all the rotational energy and protects the tower from the rotational forces that are the primary cause of tower failure. On windy days the antenna swings a bit - maybe 20 degrees - but the beamwidth is around 50 degrees so it is completely inaudible when operating.

You can see pics at AB7FS on QRZ dot com.

Another reviewer commented on the very light weight construction of the very top section and I tend to agree. Knowing what I know now, I would probably have ordered one additional straight lower or intermediate section and used an 18" section as the top section -- I would certainly avoid the very light 14" top section. I think Universal should seriously consider marketing an extra heavy duty 70' tower and draw up the engineering specs for it.

Overall, a the HD 21-70 is a great tower at a reasonable price. It carries a heavy antenna load and tolerates high winds well - so long as you protect the tower from rotational forces (but this is true for all towers :-) I would certainly buy another - with the caveats mentioned above.
 
N3NXA Rating: 4/5 May 12, 2010 12:55 Send this review to a friend
Great freestanding for aluminum but we did modify it  Time owned: more than 12 months
This was my choice of tower for the antennas I planned on installing in '94. No way to walk it up due to tight quarters after the first three sections. It was no problem for the helpers I had and willing climbers. Used a gin pole to complete the "original as purchased" HD21-70. I had a Pro67C3 at 72 feet on a 2" .250 id aluminum mast with a GP9 UHF/VHF vertical mounted at the very top. We had a nasty microburst during a storm in '95 when tornadoes actually hit the Pittsburgh PA area. I may be off a year but the end result is still the same. My experience was the same as the other gentleman. The top 14" section broke at two points and the big ole Mosley swung down and hit the tower on the right side of the beam bending several elements on that side. The tower was fine aside from that top section. Thankfully the insurance covered much of the loss so rebuilding was done. I now have an 18" top section with the appropriate rotor plate 10 feet below the top thrust bearing. The same antennas went up again using a gin pole and the climber from the club said it felt much sturdier than the original configuration. As it stands now, I have three 30", two 26" one 22" taper to the 18" top section with the flat top and thrust bearing. The tower seems much more rigid and of course easier to climb. I don't know what the exact loading would be, but it sure seems much better in the current configuration than the original as we have gone through very high windstorms and icing in the winter that would tax any structure. With the current antennas and allowing 1 sqft. each for the mast and rotor, I am still below the originally designed 21 sqft. designed capacity, but feel I could put more antenna (say a 6m or large 2m yagi) without compromising the tower whatsoever. By the way, the aluminum tower is easy to load for 80m and has very good conductivity for that type of purpose. The only negative is I would recommend replacing the bolts every so often due to dissimiliar metal degradation. Next go around I may try stainless steel as there is no shear forces on the bolts now as after all these years, what settling of the weight of antennas that may have been present on initial installation is no longer an issue. One of the original bolts were taken out last year ('09) and it was like a needle in the middle between shank and nut. I know there are the nay sayers out there regarding an aluminum tower, but this one, in its current configuration has proven to be a real winner. I see the cost is WAY up now to buy the same tower, but what hasn't gone up price in the past 10-15 years? I plan on taking this tower with me when I move and will need to buy a new set of base mounting legs. WEll worth it IMO.
 
WE8Q Rating: 4/5 Nov 7, 2009 06:12 Send this review to a friend
Strong  Time owned: 0 to 3 months
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).
 
AA8LL Rating: 4/5 Jul 29, 2007 04:44 Send this review to a friend
we modified it  Time owned: more than 12 months
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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