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Re: [TowerTalk] Rotating tower

Subject: Re: [TowerTalk] Rotating tower
Date: Sat, 20 Aug 2011 08:13:41 -0400 (EDT)
List-post: <">>
Art, re: 204BA: wonder if they can be reconfigured as a 4-el OWA design?  
Love that bandwidth!
On the 3-el 40 tip size: keep in mind that as the taper continues, the  
element length has to increased due to the taper effect. The yagi design  
programs will show this.
Gerald K5GW
In a message dated 8/19/2011 8:47:48 A.M. Central Standard Time, writes:

Someone else replied about K4JA's loss saying it was a  hurricane. Our 
winds don't get up there or haven't yet.

An elephant  gun to Asia would be good. I'm trying to avoid a mast and 
associated  hardware in the tower. Another piece of R45 above the top 
guys, at 75 lb,  seems as light as anything else I could put up there.

The small 20  above the 40 gives me the opportunity for 3 phased 20's. 
Someone suggested  a 204BA, I have some of those elements but would 
probably make it a  3L.

My 3L40 is an old DXE. From the factory it came with (what I  consider) 
huge tips. Starts out at 2 inch, ends in telescoping tubing at  0.875in. 
To me that is gross overkill at the tips. I replaced the outer 16  feet 
with 204BA elements to cut the weight but more important the wind  load. 
My neighbor K0YW has a duplicate of this ant. His element sag is  
something like 3X mine. This ant is up on a hilltop 70 ft crankup  
cranked down to about 50 ft for the past year with no probs so  far.

Gotta wonder if K4JA's pair of 40's started twisting in opposite  
directions. AB105 is stout stuff, I had some up 30 yrs ago in San Diego  

73 Art K6XT
Allison, Colorado
"One of the harshest  lessons learned from recent disasters, especially 
Katrina, is that you are  your own first responder."
...LtGen Russel Honore USA
GMCC CWOps  728

On 2011-08-19 05:54,  Pete Smith wrote:
> You're right to be concerned about twisting  loads.  K4JA, who is a 
> pretty good back-yard engineer, lost a  200-foot AB-105 rotating tower 
> with 2 40m OWAs on it in a windstorm,  and from the debris it was 
> obvious that it had twisted to  failure.  Afterward, he told me he sure 
> wished he had a shear  pin or other provision for breaking the 
> connection between his  rotator and the tower, because if it had been 
> free to move it might  well have survived.
> By the way, if you plan to phase the two  3L 20m yagis, wouldn't you be 
> better off putting the top one at 100  feet?  Or are you looking for an 
> elephant gun to  Asia?
> 73, Pete N4ZR
> The World Contest Station  Database, updated daily at 
> The  Reverse Beacon Network at, blog at 
> spots at, port  7000
> On 8/18/2011 8:51 PM, Art K6XT  wrote:
>> I've started construction of a 150 ft Rohn 45 rotating  tower using K0XG
>> base and four rings, top ring at 140 ft. Just  above the top ring will be
>> a 3L40 and possibly a small 20 above  that, like 3L.
>> I'd be very interested in any  experience or anecdotes on projects like
>> this using R45. That  tower was selected because I already own it. My
>> area has the  potential for icing. The ice I've seen is very light,
>> nothing like  back east or in EU. But I suppose its possible. Not too
>> windy, the  strongest seem to peak out around 70mph and that's  rare.
>> One issue I see is, there are no torque bars on  the tower. All its
>> torque is transmitted to the rotator on the  ground. K0XG's rings do have
>> torque bars but that doesn't help the  tower.
>> The general plot is to add antennas down the  tower above the guy rings.
>> Second 3L20, a shorty 40 Hygain, 10 and  15M.
>> Replies to k6xt at arrl dot net are FB, or  here.

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