Dominator ¾ Wave Questions

Discuss antenna construction, problems, tuning, designs...

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deeplist
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Dominator ¾ Wave Questions

Post by deeplist »

First of all, does anybody have a chart or a tuning diagram? The antenna came with markings on the elements for the frequency initally selected. Since that time, I have moved physical locations and as a result I must also change frequencies.

Also, my antenna was shot at with a rifle and now there is a hole in it. What would be the best option to repair it. I really do not want to pay to have it sent in so I am curious to see if there is anything that I can do myself.

Thank you.
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Post by Pigmeat02 »

Is it a metal antenna? There is a new product out called Alumalloy that looks like a welders rod but will melt under propane torch temps? I've got a friend who sculpts using various metals who loves the stuff for occasions when he doesn't have access to his welding equipment.

I don't know where he gets it,but I've seen advertised on television here in the States? Do a web search and see what turns up? I have no idea what it's electrical properties are? Seems like it would be worth a shot if you're not pals w/ a welder?

People seem to be drawn to take potshots at antennas? Not as popular as road signs,but close.
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Post by deeplist »

The antenna is constructed of metal. It is similar to copper pipeing but I think it may be aluminum. A while back I had a J Pole antenna that had bent and broke that a friend of mine repaired in his shop. I don't really know how he did it, but it appeared as though he took a coupler of some kind and welded the two broken pieces together.

A small story to go along with the situation: About a year ago I used the antenna for a small FM station. The station was on the air for about 6 months or so. I decided to move away and I took only the needed items with me to begin with. I recently returned to the old location to gather up the rest of my belongings (including the antennas on the mast outside) and to my surprise there was a hole shot clean through a portion of the antenna. It was clearly done by some kind of a rifle.

I really do not want to pay $400+ to purchase a new antenna when there may be a home remedy that I can use to repair the current antenna for a fraction of that. I do not have access to welding equipment, but a propane torch wouldn't be too hard to obtain.

Thanks for the suggestion however.
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Post by pcs »

It should be easy to repair metalic parts, but plastic is another matter.
It is metal that is is damaged?

Could you post a photo here?

BTW, we now stock really dirt cheap GP antennas that are actually quite decent
for small installations and easily handle 500W.
Perfect for war zones since they are cheap to replace, perhaps for Iraq :)
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Post by deeplist »

I will be able to post a photo in about 2 hrs (when I get off work and go home).
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Post by deeplist »

Image
Image
Image
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Post by Pigmeat02 »

Sheesh! They couldn't have done much worse,could they?

If you want to try a semi-DIY solution,I'd cut the damaged section out w/ a tube cutter. Then I'd get a piece of aluminum tubing w/ a slighly larger inside diameter than the ring stock. Slide the new tubing over the old and take it down to the local body shop and have them spot weld it in position. I'd be surprised if they charge you anything to do it? If they do,it shouldn't be more than a few bucks?
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Post by Pigmeat02 »

I took a better look at the pics,that stock looks a little heavier than I thought? Be certain of the type of metal it is and take to your local welder/bodyshop. They'll do essentially what I posted above,but they've got a proper tube bender to be able to do the job right? It should be fairly cheap to do.

BTW,have you taken a SWR check on it as it is? It may still work w/ the hole in it?
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Post by pcs »

Its copper. That is good, its easy to fix, you can solder it. You need to clean it with sand paper, though.
And soldering paste is welcome.

I'd bet its the exact diameter used for heating, meaning you can get pieces in hadrware store,
even pieces that have a slightly larger diameter on one side that easily slides on top of this type
of tube.

On the other hand, you could just use a small hammer and try to get it back to tubular shape, than
you can get thin copper sticky strips (I have some here, Conrad has them), they are thin flexible
copper stickers. You could wrap one of these around the injuded part, provided you cleaned it first
and used hammer to carefully get it back into shape. Than you can sodler that copper sticker with soldering
iron on both sides completely.
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http://www.pcs-electronics.com
fax +386 4 2316 128
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Post by Pigmeat02 »

The copper strips are good idea Marko. Most Hobby Shops here in the States sell the stuff in small rolls.

The guy who shot that antenna was either lucky or the great-great Grandson of Daniel Boone? ;)
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Post by pcs »

Pigmeat02 wrote: The guy who shot that antenna was either lucky or the great-great Grandson of Daniel Boone? ;)
He may have used 200 bullets and several days to get one hit :)
Best regards,
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Post by deeplist »

Yeah, and the antenna was more than 50 feet (15 meters) in the air on a mast. I was relatively pissed when that was discovered BTW.
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Post by pcs »

That's what you get when you live in a country where owning a gun or a rifle is not uncommon.

Around here that sort of thing never happens.
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Post by Pigmeat02 »

When I was kid we used to take potshots at all kinds of things. If I was a 12 year old these days there wouldn't be a safe cellphone tower in the region?

BTW,never shoot a transformer on a power pole with a rifled slug from a shotgun. Trust me.
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Post by pcs »

Why, what happens when you do? :)
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Post by Pigmeat02 »

A big explosion and a life long ringing in your ears.
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Post by pcs »

Sounds like fun :)
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Post by Pigmeat02 »

It is and it isn't? If you were 100-150 meters away it would be hilarious. When transformers blow up,they really blow up.

There's a little problem with rifled slugs from a smooth-bored shotgun? 60-70 meters is about as far away as you can shoot one w/ any accuracy? That part I knew,so I took the shot from 25 meters away. I didn't know about exploding transformers?
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Post by pcs »

Are you saying its still ringing in your ears today?

I hear noise most of the time, kind of like white noise, but I'm unsure why exactly. Maybe old age,
perhaps too high blood preasure, maybe too many episodes of microphone feedback with my earphones
on, of perhaps too many 1KV electricity shocks? :o
Best regards,
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Post by deeplist »

Is there any documentation that I can get anywhere for tuning the top two elements on this antenna? I have an swr meter but I would like to get them as accurate as possible before I put the antenna up because it is a real pain in the ass to get back down or access afterwards.
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