Utility Tower on DA site - Base Insulator Alternatives

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Fran3
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Utility Tower on DA site - Base Insulator Alternatives

Post by Fran3 » Tue Apr 19, 2016 8:33 am

This site has a utility tower about 175 feet tall on the site with the directional array. The utility tower sits on a base insulator. The base insinuator is appears to have a crack in it and we are considering alternatives.

1 - Strap the utility tower to ground and check the stations monitor points... and if still in tolerance just remove the base insulator, readjust the guy's and leave the tower grounded.

2 - Find a used base insulator (I understand this is hard to do as they frequently break when towers are taken down.)

3 - Improvise an alternative insulator. (Looking for suggestions on what these alternatives may be.)

BTW, the tower appears to be a Rohn 55 and currently has an unused Marti antenna at the top and a wireless internet dish at about 75 feet as there is no other high speed internet available at the site.

Thanks for any comments.

TPT
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Re: Utility Tower on DA site - Base Insulator Alternatives

Post by TPT » Tue Apr 19, 2016 9:36 am

Assuming this tower is not part of the array? Or is it an element in the DA?

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RGORJANCE
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Re: Utility Tower on DA site - Base Insulator Alternatives

Post by RGORJANCE » Tue Apr 19, 2016 9:59 am

There currently are several good base insulators of different sizes available.

A good sharp tower company should have no trouble at all by jacking up the tower and installing a new insulator in place of the damaged one. This has been done at a number of sites here in Wisconsin going back over a lot of years. It isn't a real big tricky thing to do.

Fossil

Fran3
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Re: Utility Tower on DA site - Base Insulator Alternatives

Post by Fran3 » Tue Apr 19, 2016 10:28 am

The tower is not part of the array.

Our tower contractor is very experienced in all aspects of tower work and can install a new or used insulator no problem.

The issues is the price of a new insulator...
- and is one really necessary...
- and if so, in the absence of finding a used one...
- how can we improvise with maybe a diy insulator

Thanks for the help !!!

TPT
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Re: Utility Tower on DA site - Base Insulator Alternatives

Post by TPT » Tue Apr 19, 2016 2:02 pm

Do you need that tall of a tower at this site if the only present use is for the wireless internet--which apparently works at 75 feet AG?

A consulting engineer could do an MOM analysis to determine the effect of shortening and grounding the present tower down to 75'

May be less expensive in the long run than trying to find an insulator, jacking up the tower, running monitor points, etc.

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kkiddkkidd
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Re: Utility Tower on DA site - Base Insulator Alternatives

Post by kkiddkkidd » Tue Apr 19, 2016 6:17 pm

Closely check your monitor points and antenna monitor readings and only then firmly (but temporary) bond the tower to ground. If the antenna monitor and MP's don't change AND if the tower isn't mentioned on the license, lift it, get the old insulator out and add whatever adapter plate might be necessary and adjust the guy length. If it is described in the license then all bets are off. The FCC probably won't care if the tower is there, gone, grounded or insulated as long as it is not mentioned on the license and MP's and monitor readings are correct.

_If_ grounding it changes the monitor points noticeably (and it probably will), be prepared to detune the tower after permanently grounding it. This is probably cheaper than a new insulator. DO NOT go cranking on phasor knobs until the whole situation is understood. And even then only after the current turn counters are logged and verified as functional.

On the other hand, as previously suggested, a quick MoM model would pretty accurately predict the effect (affect?) of grounding the tower without getting your hands dirty.

Later,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

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Deep Thought
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Re: Utility Tower on DA site - Base Insulator Alternatives

Post by Deep Thought » Wed Apr 20, 2016 9:39 am

kkiddkkidd wrote:DO NOT go cranking on phasor knobs until the whole situation is understood.
I can pretty much guarantee this tower will blow out the pattern if grounded.

You should be able to detune the tower and get the monitor points back 'in' without touching the phasor. In fact, that will be the primary indication that you did it correctly. A proper detuning kit will cost you around $3,500 so consider that against the cost of replacing the insulator. Jacking up a 175 foot Rohn 55 and replacing the insulator will probably be cheaper overall.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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