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Author Topic: AM Tower Grounding Co. Project pics & dscrptns.  (Read 26044 times)
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Superhet66
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« on: May 03, 2010, 08:43:45 PM »

Some good pics and info.

Scroll down below the map of the US.

The station call signs that are highlighted in red can be clicked on.

The pics that show up are thumbnails and can be clicked on also for full size and resolution.

I picked up some good info. Some of the comments are pretty funny.

                                                      Enjoy,  D.


                           http://www.kkbc.com/projects.htm


* Ground - Radial array..jpg (73.67 KB, 640x480 - viewed 1514 times.)
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WA1GFZ
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« Reply #1 on: May 03, 2010, 08:59:46 PM »

I would love to see a picture of that parking lot after the tower takes a good hit to see if the paving explodes.
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Superhet66
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« Reply #2 on: May 03, 2010, 09:11:10 PM »

Dark Thoughts.... Shocked

 It would be interesting...Scroll down for lightning vs. concrete explosion on link below.

            
 http://forums.mikeholt.com/showthread.php?t=111891  
                    
                  
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WA1GFZ
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« Reply #3 on: May 03, 2010, 09:31:39 PM »

I would have put a layer of sand or small rock between the radials and paving.
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Steve - WB3HUZ
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« Reply #4 on: May 03, 2010, 09:43:55 PM »

Interesting pix. They have a local (to me) station on there.

http://www.kkbc.com/wmbg.htm
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flintstone mop
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« Reply #5 on: May 03, 2010, 09:52:51 PM »

I'm starting to drool, seeing something done right and such nice workmanship

Fred
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Fred KC4MOP
Superhet66
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« Reply #6 on: May 03, 2010, 10:01:36 PM »

All that copper and high power gear is eye candy  Wink

As you read the stories you find a lot of thier work is undoing botched contractor work. Copper theft is another big issue.

It looks like hard work but interesting in that every site is a new challange.
I wonder what changes in propagation have been seen before and after these boys do a job.    ??
                              D.
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K5UJ
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« Reply #7 on: May 03, 2010, 10:36:30 PM »

that looks like kevin kidd's work.

I was right (now that I have looked at the web site) AM Ground Systems. 

That website is a great place to look at AM ground construction.   That first photo looked familiar and now I realize I saw it a year or three ago.   If you really want to do your 160 m. ground right, do what they do (or hire them hi hi). 
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N3DRB The Derb
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« Reply #8 on: May 04, 2010, 04:42:03 AM »

yeah, I found that looking for info on am BCL grounding, and so far I haven't found better documented case by case work out there.

the one "attaboy letter" he posted, the GM claims that that the stations coverage just about doubled after they put in the new radial system.

There's also a excellent story  on one of the station job threads about how someone in the past had tried to use non-copper as radials and tower grounds and how useless and rusted out it was. I was reminded of the recent thread on here about using galvanized wire and such.

my system I put in just last year is all garbage now save for the 2 connections I silver soldered, every mechanical clamp connection is crap. this time it's getting silver brazed together back to the service connection going past that right to the future 160 meter vertical T feedpoint.

I'm sure my half assed effort last year is what caused most my electrical problems during operating season. Never again.
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K5UJ
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« Reply #9 on: May 04, 2010, 07:30:03 AM »

I'd like to know where he gets the copper mesh.

Yep Derb, many hams try to save a few bucks and do radials on the cheap.  It never pays off in the end. If you are planning on staying put for several years it pays to spend the bucks and go with copper.   Many hams can't deal with the idea of spending hundreds of dollars on wire then laying it on the ground.  They have the signals to show for it. 

If it makes you feel better saving money has been tried by the pros.  I heard a story a few years ago that at one time, WOR 710 tried aluminum wire for radials and that experiment ended after a few months with disappointing results.  The Al didn't hold up well in the ground.

Rob
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KM1H
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« Reply #10 on: May 04, 2010, 09:17:10 AM »

WOR is in a salt marsh so its no wonder Al didnt work.

Several AM stations who were losing coverage due to the 128 copper radials disintergrating and not being able to lay new copper due to development received FCC permission to go with elevated radials. They then had to reduce power to conform to the original POP results.  Lots of stuff on Google.  One local station uses the metal roof of the 4 story building the tower sits on and gets out real well.

Carl
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Superhet66
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« Reply #11 on: May 04, 2010, 09:37:49 AM »

It would seem an investment in a properly engineered ground/radial system might off set or even pay for it self over time.
 If the upgrade / repair results in having to reduce power out for the same TX coverage. Reduced electric bills ( NORTH EAST electric bills!  Tongue  ), reduced load on the finals and related equip. and fewer service calls ( in theory ).
I'm sure this is part of how station GM's are sold on Grnd. upgrades.
A symetrical or at least predictable prop. pattern has to help target expensive advertising also I guess...
(  geeze, I sound like a salesman  Cool  ).

I'de be curious as to the material cost alone.

                                     Blah blah blah,   D.
                                             
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flintstone mop
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« Reply #12 on: May 04, 2010, 09:52:42 AM »

I agree that it can get a little pricey to do it right, but look at the results.
The screen is only needed close to the tower, as the pic shows a couple posts down from the top.

Here's a place that sells mesh: 

http://www.darbywiremesh.com/index.html

There's another thread on AMFONE where OPCOM is considering using plastic coated welded fencing. Might be a substitute for the real thing for the near field requirement.

Fred
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Fred KC4MOP
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« Reply #13 on: May 04, 2010, 10:30:22 AM »

A source for copper grounding strap and supplies is from a Polyphaser distributor.

http://www.polyphaser.com/products/prod/gnd/acc/
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flintstone mop
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« Reply #14 on: May 04, 2010, 11:48:50 AM »

Any guesses how many feet square the screen is at the base of the tower in the pic about third post down?
30' X 30' Huh?

Fred
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Fred KC4MOP
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« Reply #15 on: May 04, 2010, 12:23:51 PM »

Quote

That's a great site Steve Grin Grin Loved looking at the pics. I would like that kind of work but I do not like to climb towers. Of course I'm too old now, but if I could, I wouldn't!!
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K5UJ
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« Reply #16 on: May 04, 2010, 02:18:33 PM »

<<Here's a place that sells mesh:  >>

unfortunately it looks like another one of these places where you have to request a quote.  I hate it when they do that.   Huh   I just move right along my merry way...

I've heard conflicting things about mesh.  I heard you can get these eddy currents that somehow compromise the performance of the ground system.  Sure looks like it ought to work great especially close in where you can have all that surface area for braising the wire.  I'd put it down on gravel so as to not start a fire and throw more gravel on top of it when done.
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Superhet66
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« Reply #17 on: May 04, 2010, 02:26:43 PM »

I like how the 5/8 copper pipe and couplings are utilized. ( relatively cheap and available )
They even incorporated existing copper plumbing ground material into thier new work.
I guess with skin effect, RF sees that pipe as pretty "wide" electrically.


* Copper pipe.jpg (53.19 KB, 640x427 - viewed 517 times.)
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N3DRB The Derb
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« Reply #18 on: May 04, 2010, 09:16:21 PM »

I like these guys.


http://www.gacopper.com/index.html

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KM1H
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« Reply #19 on: May 05, 2010, 08:33:13 AM »

I dont see how copper mesh maintains its effectiveness if all the crossing points arent bonded. After a while you have a million diodes.

The welded and galvanized 2x4" mesh on the other site is what I had used except it had been plastic dipped; it came in 4' x 50' rolls. Their 24" x 100' rolls would be ideal and the weight is low. Cut in half or thirds for 80M.

Carl
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Superhet66
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« Reply #20 on: May 05, 2010, 09:52:59 AM »

I dont see how copper mesh maintains its effectiveness if all the crossing points arent bonded. After a while you have a million diodes.

Some of the mesh sheets I've seen are actually an "expanded lath" and have no junction points except the perimeter. Alternating slits are punched/cut into a sheet and pulled apart like paper dolls. Aluminum lath is made the same way for mud work in tile and masonry work.
Interesting observation re. the diode effect.
The chicken wire style copper mats would be an issue I guess.

High performance on  80 / 160 can be some work I guess!
                                                                                              
                                                                                 D.


* Copper mesh.jpg (71.46 KB, 640x480 - viewed 530 times.)
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k4kyv
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Don
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« Reply #21 on: May 05, 2010, 10:31:14 AM »

I'm not sure that mesh is any better than having many radials up near the tower, something like the normal 120 radials 1/4λ or more, but maybe twice or 4 times that many near the tower base, using short radials perhaps 50 ft. long or less.

I have read in several engineering books that it does absolutely no good to tie the far ends of the radials together with a perimeter wire; it's a waste of copper.  So wouldn't the same principle apply in close proximity to the tower base, regarding the wire in the mesh that does not run out radially from the common point?  The best way to "fatten" the radials would be to add more of them.  Maybe one perimeter wire that bonds all the short radials to the main ones would serve a purpose, since that would give the current induced in the short ones somewhere to "go" besides into the lossy earth.
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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k4kyv
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Don
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« Reply #22 on: May 05, 2010, 10:40:11 AM »

The dawg  house (inside the fence near the tower) at KKBC looks amazingly like the one I just built.





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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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W8IXY
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« Reply #23 on: May 05, 2010, 10:50:35 AM »

When we were building a 6 tower AM directional antenna system here in Cleveland, back in 1999, I was asking the tower crew if they used copper mesh under the tower bases any more.  The said they found no measurable difference between using a 24' x 24' mesh at the tower base or simply attaching the 120 radials to the copper strapping secured around the tower base.

But I found out another interesting point.  At that installation we used half wave lengths of #10 wire instead of quarter wave lengths for the radials.  The increase in efficiency was just a few percentage points, but for AM broadcast, even a 5% difference could help.

As for ham radio though, unless you wanted to squeeze all the efficiency you could out of a Marconi type vertical radiator (QRP use?), its doubtful you could even perceive any difference between 1/4 wavelength and 1/2 wavelength buried radials.

There is a company that sells and installs above ground radial systems for AM broadcast towers that claims that 6 quarter wave above ground radials result in effectively the same field strength at one kilometer as a system using 120 buried quarter wave radials.  The disadvantage of above ground radials is that you do not have a nice dissipation system for the lightning strikes.

Also, when we built that system 11 years ago, we installed static dissipators at the top of each tower (6 towers @ 260' each).  The dissipators are made of a cage of metal rods, each having hundreds of sharp pointed spikes about 3 inches long attached.  In 11 years, we have never had any evidence that any of the towers has ever been struck by lightning.

.....stuff we learned as broadcasters that we can use at home!

73
Ted  W8IXY

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WD8BIL
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« Reply #24 on: May 05, 2010, 11:10:32 AM »

What station was that, Ted?
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