[TowerTalk] High VSWR

Fri Aug 30 18:51:24 EDT 2019

What an incredible story. That is one heck of a piece of hardware. Very sorry to see what happened, but it does look recoverable, at least to some extent.

I have a question about the hoisting configuration. The discrepancy between the manual's 6000 lbs of force to hoist the mast and antenna versus what Doug computed and actually found (e.g., the truck tipping), is disturbing. What I don't understand is the angle of the hoist rope to the tower on the winch side. My understanding is that the force increases as the angle increases, so that the least amount of force is required when you pull straight down. Does the manual recommend the large angle, and if so why would that be?

Seems to me that it would be best for the hoist rope to run straight down the tower to a winch mounted there (which is where I mount the winch I use to tram antennas up my tower), or to another pulley mounted at the base, which would turn the rope horizontal so it can be mounted to a truck that would drive in away from the tower to hoist the mast. Or, it could run to the fixed winch Doug installed. No doubt, a beefy pulley and mount would be required for this, but I believe it would significantly increase the mechanical advantage.

My understanding is that properly chosen and installed wire clips should have held, but personally I prefer a swaged sleeve (perhaps, in a case like this, with wire clips for belt and suspenders). Depends on whether the mount for the loop at the mast can be opened or disconnected without having to disassemble the wire rope termination.

I'm also perplexed by the diameter of the U-bolts securing the largest elements. They look pretty skimpy to me (nearby bolts are much heftier.) My "little" Cal-AV 2D-40A, with two full-size elements, has much beefier U-bolts. And if only one pair of U-bolts secures each of those massive elements, I'd question the design.

73, Dick WC1M

-----Original Message-----
From: Glenn Pritchard <gpritchard7000 at gmail.com> 
Sent: Wednesday, August 28, 2019 11:04 PM
To: Wes <wes_n7ws at triconet.org>
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] High VSWR

What in the world happened???? Was the lock mechanism not in place?
I’ve installed many of these over the years for ATC systems but have never seen this happen.

Glenn, VA7UO 

Sent from my iPhone

> On Aug 28, 2019, at 7:14 PM, Wes <wes_n7ws at triconet.org> wrote:
> 
> For those that may have missed the link to Doug's build photos here it is:
> 
> http://w6dsr.com/LP1005AA/index.html
> 
> Doug, I'm sorry about your loss.  But if the mast isn't bent, which the one post-failure photo I've seen (Dave I'd like to see the others) seems to indicate, then you still have tower, rotor, and mast.  I'd put up a less heroic "ham-style" stack and get on the air.
> 
> Wes  N7WS
> 
>> On 8/28/2019 6:32 PM, David Gilbert wrote:
>> 
>> That certainly is tragic, although I'm greatly relieved that it doesn't appear anyone was hurt.
>> 
>> It is truly amazing to see the thought and effort you put into that antenna, and a tremendous shame to have it come down like that.  I hope you decide to rebuild instead of finding a different hobby.
>> 
>> This is one case where being able to post the pictures to the reflector would have been desirable.  I'm sure you don't want to be bothered by that, so if anyone wants to see them I will forward them for you.  For those interested, send me a private reply ... not to the list.
>> 
>> Take care,
>> Dave   AB7E
>> 
>> 
>> 
>>> On 8/28/2019 6:12 PM, Doug Ronald wrote:
>>> I'm too upset to do a complete post mortem, but the antenna lowered to about the point in the attached image, and then there was a failure in either the 1/2" wire rope, or the wire rope slipped out of the 4 clips I had at the antenna end. My calculated tension in the cable was 14,900 pounds with the antenna at the horizontal position, but at 45 degrees, the tension would have been only 11,000 pounds or so.
>>> The clips were to be torqued to 65 ft. lb. but not overtightened such that the wire rope is crushed. I don't have a torque wrench, so I guessed at the 65 ft. lbs. I guess I didn't have them torqued enough, but there was no slippage when I put the antenna up a couple years ago using the same rope, and the same clips.
>>> 
>>> -----Original Message-----
>>> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf 
>>> Of David Gilbert
>>> Sent: Wednesday, August 28, 2019 16:51
>>> To: towertalk at contesting.com
>>> Subject: Re: [TowerTalk] High VSWR
>>> 
>>> 
>>> That story would be a lot more interesting if you actually explained what happened.
>>> 
>>> Dave   AB7E
>>> 
>>> 
>>> 
>>>> On 8/28/2019 3:30 PM, Doug Ronald wrote:
>>>> Hmmm, my VSWR came up a little high this afternoon, see my QRZ page 
>>>> to see why.
>>>> 
>>>> 
>>>> Actually, I shouldn't joke about it - I'm totally devastated.
>>>> 
>>>> 
>>>> 73 all,
>>>> 
>>>> -Doug Ronald, W6DSR
>>> _______________________________________________
> 
> _______________________________________________
> 
> 
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk