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Author Topic: Theory to Hardware - Grounding Systems  (Read 725 times)
KI4MFH
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Posts: 34


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« on: October 21, 2005, 06:02:54 AM »

Hello.  I was stupid, and let my license expire some 25 years ago.  I recently passed the General test and I am trying to set-up a reasonable shack.  Needless to say, things have changed a bit in 25 years!

My question pertains to grounding systems – lightening and RF.  Before you flame me, I have read the many posts pertaining to protection, and found some excellent discussions.

I think I understand the following to be reasonable assumptions:

Station Ground (inside shack) – Common tie for all equipment and direct connect to external grounding system with special attention to bonding.

External Grounds – All rods bonded together, and external protection for towers and coax cables prior to entry.  This would include shield grounding, as well as lightening protection.

Surge protection is a discussion for a later time.

The problem now is that I suffer from information overload.  I understand the theory (maybe), but am now faced with the dilemma of taking theory and developing a practical hardware configuration.

External Ground Point – I would like to purchase or fabricate a single box that hangs outside of the shack where all cables enter - contains all lightening arrestors, coax shield ground connections, etc.  Question here – I have seen several remote coax switches and would like to include on within the External Ground Point.  Pros and cons of this?

Bonding.  I plan to use 3” copper strap from the Station Ground system to the External Ground Point.  How do you bond the straps to a 5/8” ground rod?  Planning to use 2” straps between multiple ground rods, to include the A/C Service ground.

Lightening arrestors – Is insertion loss greater on 2 meters?  If so, how do you deal with VHF/UHF protection?

Multiple connectors and mixing types.  Nothing is free.  A significant number of connectors come along with the addition of lightning arrestors and coax switches.  Also, type changes – N to 259 and such introduce adaptors.  Are we looking at significant insertion loss?  For example - N connectors on hard-line to VHF antenna fitted with female 259 and transceiver 259 to N.  Are losses significant enough to change the connectors? Not even sure if there are 259 connectors for ½” hard-line.

At this point I am looking for first a validation that my ideas are sound and conform to best practices, after that, looking for equipment recommendations and suppliers.

Based on my research, it is evident that the grounding system is the foundation for building a shack, and influences all future hardware/antenna additions.  So, I want to do it right the first time.

I hope this makes some sense, and excuse my long-windedness.
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KC0VCU
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Posts: 138




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« Reply #1 on: October 21, 2005, 07:31:17 PM »

Rather new to this myself, but the one thing that I would consider somewhat seprately is lightning grounding for any tower you may have. This is possibly the only ground that you may want to have distinct from your equipment grounding procedures.

Of primary concern is the fact that any tower you may be using being physically tied to the ground through a concrete block. If this provides an electrical ground that is shorter than the path you set up through your equipment ground, you can expect any lightning strike to your tower itself to go through the concrete block, potentially converting some of the water within it to steam and destroying its integrity. This is one place where you will want to have a strap going to a ground rod that is local to the tower.

Beyond that it sounds like you have a reasonable plan. How practical it is, is definately outside of my ability to comment.

73
-Rusty - kc0vcu
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AA4PB
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« Reply #2 on: October 23, 2005, 10:42:08 AM »

You always want to have several ground rods right at the base of the tower for lightning protection.
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ZAKIR
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Posts: 45




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« Reply #3 on: October 27, 2005, 05:18:28 AM »

Okay... Another question... I'm thinking about putting up a large whip to play with. It would go directly into the Yaesu FC-40 tuner... I would want to protect the tuner from lighting as well as my radio in this situation, meaning that putting a lightning anneatur (sorry, I have no idea how to spell that!) in between the tuner and the radio, where there is coax, would it be possible to put something between the tuner and the antenna, which is just a wire connection? The other half of the tuner goes to ground.

Thanks,

Zakir
KC0VAA
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KC0VCU
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Posts: 138




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« Reply #4 on: October 27, 2005, 08:15:17 PM »

Your best bet for this would probably be to put a double poll switch set up so that when you are operating the switch connects the antenna tuner to the antena, and when you are not operating, it connects the tuner to a dummy load. As part of this it would really be a good idea if the antenna was shorted to ground at the same time.

You may want to actually put in two seprate switches, the first switch attaches to the antena tuner and switches between the second switch, and the dummy load. The second switch toggles the connection from the antenna to ground, and the antenna to the first switch. The down side of this is that the possibility exists for you to end up having the antenna tuner attached to an unloaded cable. Not generally a problem, except when you go to transmit. The SWR is going to be way off.

Even with this set up, you will want to get zener diodes installed on your antena wire, outside of your shack, that short the mast to ground in the event of a lightning strike.

73
-Rusty - kc0vcu
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K9KJM
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Posts: 2416




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« Reply #5 on: November 04, 2005, 08:55:14 PM »

Congratulations on going with the copper strap the first time!   I strongly suggest just getting a nice sheet of the same type of copper attached to a small sheet of plywood right at the point where your coax all enters the building (Just inside the building) Upscale roofing companies that install copper roof flashing is a good source for copper sheet at a fair price. Depending on how many arrestors or switches you plan, a sheet around 12" by 12" should work pretty good. Your 3" (Or wider) copper strap then running outside with no sharp bends. That way all arrestors, switches, etc are indoors and out of the weather. Remote switches will fail, sooner or later.....
I use the good old B&W (Barker and Williamson) type that put all unused antennas to ground. And Alpha Delta strip line for UHF/VHF These switches are mounted right on the copper sheet where the coax enters the building.
The only time you really need lightning arrestors is when you plan to use that antenna during a lightning storm. Check into I.C.E. (Industrial Communications Engineers) for low prices on good quality protectors. Polyphaser is also good, But costs more.....
When not actually operating, I keep all antennas switched to ground.
Type N connectors are better for UHF, ICE and Alpha Delta make both types. Just run the 3" strap outside and then at your first ground rod, Run a short length of 1" wide strap silver soldered to the wider strap down to the ground rod and clamp the strap to the ground rod with a stainless steel hose clamp or two.
The silver solder to get is called "Silfoss" is around 15% real silver, about a buck and a half each stick from a welding supply company. (This is the stuff used by A/C contractors) Use MAPP gas in a small hand held torch to flow the silver solder.
All ground rods should be spaced about twice the distance apart as the depth. (8 foot deep rods should be spaced about 16 feet apart in normal soil.
You are correct, Everything gets bonded together.
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