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Author Topic: PolyPhaser Grounding Question  (Read 2937 times)
KC2NNS
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« on: May 22, 2007, 08:03:48 AM »

Hello all. I am setting up a low power (35w) 2-meter repeater on a rooftop and I (of course) want to use the proper grounding mechanism for it. I'm a new ham so I did some homework and came up with the Polyphaser coaxial grounding products.

Perhaps I didn't look hard enough, but I did not see a product that operates at only 35 watts. My question is this: Model IS-50UX-C1 seems to have all the right specs with the exception of a power rating of 125-375 watts. Will using this product impede on the operation of the repeater or will it be sufficiant?

Any suggestions would be greatfully accepted. Thanks!
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KB9CRY
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« Reply #1 on: May 22, 2007, 01:13:57 PM »

Yes, you want something rated at higher power than what you'll be using.  Higher rating is not bad; they will all do the same job from the lightning side of things.
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AA4PB
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« Reply #2 on: May 22, 2007, 04:38:59 PM »

I believe the power rating specification is the maximum power range, depending on frequency and SWR. You can always operate it at lower power ratings so it should be fine for your application.

Remember that you still need a good single point ground at the building entry. The device can only prevent a surge on the center conductor referenced to the shield. You must provide a low impedance path to ground from the shield.
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K9KJM
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« Reply #3 on: May 23, 2007, 01:00:56 AM »

The Polyphaser Model IS-50UX-C1 is fine for your application. Also, I.C.E. (Industrial Communications Engineers) Sells good arrestors at a good price.
What is MUCH more important than the actual device is the proper bonding of all grounds, And the installation of the ground system.
For good information see: http://members.cox.net/pc-usa/station/ground0.htm
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KD5PKS
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« Reply #4 on: May 24, 2007, 09:01:09 AM »

Surge arrestors are OK but if you're on a budget, then your money would be better spent on proper grounding and add coax surge arrestors after proper grounding is installed. I would also stress exactly what the previous two posts say and add that the surge arrestor will not do what it was intended for without proper grounding.
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KB9CRY
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« Reply #5 on: May 24, 2007, 11:16:49 AM »

And to reiterate, "proper grounding" as stated previously means a single point ground rod just outside where the cables enter the house, a shack ground which is run outside to this SPG, and tieing the SPG via outdoors, to your electrical entrance ground rod.  Only mechanical or exothermic connections are allowed by NEC.  
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AA4PB
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« Reply #6 on: May 24, 2007, 01:38:14 PM »

your money would be better spent on proper grounding
----------------------------------------------------
Surge protectors are pretty much worthless without proper grounding.
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KB9CRY
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« Reply #7 on: May 25, 2007, 04:05:41 AM »

your money would be better spent on proper grounding
----------------------------------------------------
Surge protectors are pretty much worthless without proper grounding.



Actually you need everything for a properly designed and installed grounding system.  You need ALL the components to be in place for it to work properly.  Eliminate one and you give Mother Nature a route to bite you by.
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K1CJS
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« Reply #8 on: June 01, 2007, 02:05:52 PM »

"Actually you need everything for a properly designed and installed grounding system. You need ALL the components to be in place for it to work properly. Eliminate one and you give Mother Nature a route to bite you by."

Just remember this--even if you have a properly planned and installed grounding system, Mother Nature is a fickle woman--she may just 'bite' you anyway.  The grounding systen only reduces your chances of damage, if you get struck directly by lightning, you may end up with a vaporized grounding system, vaporized cables and damage to your home and equipment.

A grounding system is like insurance, it reduces the possibility of equipment damage by static charges and induced spikes, but there isn't a grounding system made yet that will stop any damage if the lightning strikes your house or even strikes close to your installation.
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K9KJM
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« Reply #9 on: June 02, 2007, 01:15:13 AM »

Quote:   "Just remember this--even if you have a properly planned and installed grounding system, Mother Nature is a fickle woman--she may just 'bite' you anyway. The grounding systen only reduces your chances of damage, if you get struck directly by lightning, you may end up with a vaporized grounding system, vaporized cables and damage to your home and equipment.

A grounding system is like insurance, it reduces the possibility of equipment damage by static charges and induced spikes, but there isn't a grounding system made yet that will stop any damage if the lightning strikes your house or even strikes close to your installation."

More old wives tales and plain old B.S. above.

A properly installed system CAN survive direct lightning strikes with NO damage to equipment!
As all modern day cellphone towers, Police, Fire, Broadcast, etc tower sites do!

It does take some effort to install a good system that will withstand repeated direct lightning strikes with no damage to your equipment, But it CAN be done by an average ham.
Again, Good info here: http://members.cox.net/pc-usa/station/ground0.htm

Many years ago power companies did extensive research and found that a single #6 copper wire would withstand over 90% of all direct lightning strikes.
They also found that it was cheaper for them in the long run to simply repair the damage on the less than 10% of cases where a "super" size lightning strike would vaporize that #6 wire, Than to use larger conductors on EVERY pole.
(Check out any power company substation where they Do NOT want to have any damage. You will find #2/0 copper conductors from the steel framework to the buried ground grid.)
Tall commercial towers that take many hundreds, If not thousands of direct strikes over the years do NOT have the heavy #2 copper ground wires "vaporized" by lightning.  
We recently replaced the commercial 4 bay J pole antenna on our county repeater system (On the very top of a 500 foot tower) Because of its age (Over 25 years old) The top antenna had holes burned right thru the aluminum from lightning!   Never any damage to the repeater!  (DC grounded J pole) Polyphaser at the single point ground.

 
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W2IRT
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« Reply #10 on: June 08, 2007, 02:45:31 PM »

A question, if I may. I just bought a number of Polyphasers at Dayton (for control lines, 120 AC, 240 AC, telephone, CAT-5), and I'm Cadwelding AWG#4 wire to 19 ground rods on my property. My question is the SPGP itself.

I know the theory is to put a solid copper panel in the station, mount the Polyphasers to it and use 2 or 3" copper strapping to connect to the bonded ground outside the building. I have about a 4 or 5 foot run to the ground system from inside my station.

That said, I'm extremely worried about inviting lightning into my home by placing ALL my protection behind the desk in the shack. Thor's Finest has just traveled 5 miles through normally-resistive air and hit my tower, let's say. What's to prevent it from jumping a foot into the wall and wreaking havoc with the internal wiring while it's working its way through my bonded ground?

I'm trying to implement this as close to "ideal" as I can, but it really seems counter-intuitive to route lightning protection to a single-point panel in a home. I can see it in a commercial transmitter building or cell site, but to a house?

Comments greatly appreciated here or via e-mail. I'm going to start laying the ground wire in 2 weeks or so.

73,
Peter W2IRT
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K9KJM
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« Reply #11 on: June 08, 2007, 11:14:10 PM »

Do space your ground rods apart, The rule of thumb is twice the distance apart as the depth. (8 foot deep rods spaced 12-16 feet apart) To space them closer is a waste of ground rods.
Commercial tower sites use at least TWO six inch wide copper straps from the "single point" ground buss that is located just inside the building where the coax enters........    I would run at least one 6 inch, Or two 3 inch straps to your ground system outside.
It is also important to make sure your coax shield is grounded both at the top and bottom of your tower.
(Usually no extra grounding is needed at  the top as long as your antenna boom is at DC potential)
For good lightning protection info see:
http://members.cox.net/pc-usa/station/ground0.htm
True hard "Silver Solder" as used by the air conditioning repair trade can also be used for bonding copper outdoors (NOT to be confused with the "soft" silver solder sold for plumbing use) Do NOT use lead/tin solder!!!   The stuff I am refering to is actually a high silver/copper/nickel content brazing type welding rod, Sold at most welding supply stores, and can be flowed with a small hand held torch with MAPP gas.
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W3LK
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« Reply #12 on: June 09, 2007, 04:52:04 PM »

Kenneth:

What's your recommendation for a roof-mounted tower (Glen martin) - 2/0 from the tower to the SPG?

73,

Lon - W3LK
Baltimore, Maryland - soon to be Naugatuck, Connecticut
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K9KJM
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« Reply #13 on: June 09, 2007, 09:16:35 PM »

A roof mounted tower is grounded to the ground grid with strap or heavy copper of it's own. Those ground lines do NOT run to the Single Point Ground Plate.

The Single Point Ground plate would be grounded with strap, And then out to the same ground grid, But entering the soil before attaching to the tower ground lines (Going first to a ground rod of it's own)   However, All ground rods and grounds are bonded together, Outdoors, underground. (Including power, Phone, etc)
A basic of lightning protection is to have all downconductors attach to a ground rod before they are bonded to the rest of the system.
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W3LK
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« Reply #14 on: June 10, 2007, 12:09:04 PM »

Kenneth:

Thanks for the explanation. As you might suspect, this is what I am looking to do at my new location.

Lon - W3LK
Baltimore, Maryland - Soon to be Naugatuck, Connecticut
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