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Author Topic: Materials for Grounding Station  (Read 2664 times)
KE5QKT
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Posts: 76




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« on: December 29, 2007, 05:24:56 PM »

I have a few questions regarding selection of materials for building my station ground. Since I pretty much understand the general theory regarding putting together such a ground system, there is no need to refer me to the typical links that explain that, as I've already read most of those.  Now for my questions:

1) Is there any problem in using copper braid to connect my equipment to my copper bus bar (that resides on desktop behind gear) or should I use copper strap?  I know strap is lower in terms of inductance, but the braid is easier to work with. These connections will only be about 6" long.

2)  However, I am using 2 runs of 2" copper strap to connect my bus bar to a copper sheet(sheet is mounted to 3/4" plywood) behind my desk. On the sheet, I have mounted an Alpha Delta antenna switch and an ICE protector.  I plan to bond both of these devices to the copper sheet using strap (and/or by removing some paint from the underside of each device) and will also attach #4 copper wire to the grounding lug on the ICE and to one mounting hole/screw on the the switch. The #4 wire will then go through my exterior wall (brick and plywood) and be attached to a system of grounding rods (including bonding it to the service panel ground rod). I know that strapping is highly recommended for this purpose, but it would be a pain to route strapping thru my exterior wall; the #4 wire would be much easier to deal with in terms of drilling holes thru wall also in terms of attachmnet to the ground rods. Any problem with this approach?  

3) My Astron RS35M power supply does not appear to have a chassis ground lug. I assume this is because RF doesn't flow thru the supply and since its chassis is already connected to the wall outlet's safety ground. Therefore, no need to have a ground strap running from the pwr supply chassis to my bus bar, correct??

Thanks,

Doug
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K9KJM
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Posts: 2415




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« Reply #1 on: December 30, 2007, 02:04:11 AM »

"Braid" Is what girls do with hair........  The ONLY place you will find copper braid in a modern radio station tower site is to things that must move, Like to bond a steel door to a steel door frame.

I do not run extra grounds of any type to the actual radios. The place to ground it all is at your "Single Point" ground panel, Your nice copper sheet. ONLY.
Adding more grounds will just create ground loops. (Radios are already DC grounded through the coax shield.)
The object is to provide a good ground for lightning strikes before your equipment, Not to have your equipment have another ground for lightning to go THROUGH your radios to get to ground!

Along with the radios, I would not run any extra ground to your power supply.

I live on a hill, With very tall towers and do take direct lightning strikes most every large storm. With NO damage to equipment. Same with modern day properly protected Cellphone, Police, Fire, etc tower sites.

It IS important to run your nice copper strap out from your ground panel to your ground system.
I would find some way to get that strapping through the wall. I have run it through concrete block building walls by simply drilling  a series of small holes in the mortar joint, Then chipping the remaining mortar out and sliding the strap through that small slit.  Usually it is an easy matter to make such a slit through the mortar joints.

(BTW, 2" wide copper strap is worlds ahead of what most ham operators use, BUT main grounding using 2" wide copper went out at commercial tower sites in the 1960's.    Depending on the mass of heliax or coax shield coming down the tower, Most modern day tower sites use SEVERAL 6 inch wide copper straps.........)
These are what you would call "Mission Critical" tower sites that just cannot afford to go down because of lightning damage.
As you know, Lightning strikes come in all different sizes. My guess is that your 2 inch wide copper strap should be able to handle something like 98% of all lightning strikes.
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KB9CRY
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« Reply #2 on: December 30, 2007, 06:09:33 AM »

1) No
2) No
3) Correct not needed.

Looks like you've got it all covered.  I didn't use strap in my setup but as stated it is the best method of bonding between the inside and the outside SPG.
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AB8XA
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Posts: 30




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« Reply #3 on: December 30, 2007, 06:51:56 AM »

I've read the chassis ground lug for the Astron RS-35 is on the bottom of the power supply.  If you're following the ground everything philosophy, you'll probably want to ground it as well.  Most followers of this camp advise against braid.

I don't ground my radio or power supply either.  There's considerable debate between the two schools of thought.

http://www.eham.net/articles/8951
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KE5QKT
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Posts: 76




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« Reply #4 on: December 30, 2007, 01:31:02 PM »

I read with interest Steve's article and the ensuing thread, but it appears to me that the most knowledgable source relative to grounding was the final poster on that thread, OceansRadio who is often referenced on eham http://members.cox.net/pc-usa/station/grounding.htm.  In going thru his material it appeared to me that he advocates bonding your station equipment to the SPG as part of a total protection system.  Given his references and experience, that seems like sage advice to me which I plan to follow.  This is also confirmed in the ARRL Handbook.

Yep, I lifted up my Astron and sure enough there was a grd lug on the bottom, so it would seem that it should also be bonded to the SPG following the same logic.  

I must admit this is one of the most controversial topics that I have seen, but when it comes to good engineering practice, its hard for me to imagine that there would not be more consensus on approch Smiley

Thanks guys,

Doug
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AB3CX
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Posts: 793




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« Reply #5 on: January 14, 2008, 10:47:58 AM »

I find it hard to believe a Ham would rely on daisy chained coax shields for the interconnects of chassis grounds. Coax can develop connector faults, and depending on the resistance of your solder connections, this is asking for ground loops. A common ground bus with a connection to each piece of equipment is usually relied on to eliminate ground loops
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K9KJM
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« Reply #6 on: January 14, 2008, 11:39:35 PM »

AB3CX is out of touch with modern day lightning protection systems. As used on Police, Fire, Cellular, And other "mission critical" radio systems that CANNOT afford to go down due to lightning strikes.

The idea to run "braid" (What girls do with hair) to each item has been shown to be NOT the way to do it.
This idea was popular in the 1950's.

The SINGLE POINT ground panel is what all commercial tower sites use nowadays.
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KE5QKT
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Posts: 76




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« Reply #7 on: January 19, 2008, 06:05:46 AM »

Just as an update, I have changed my materials for bonding my equipment to the bus (will now use 1/2" OD copper tubing instead of braid) and for bonding my single point ground panel(copper sheet)to the system of ground rods(will now use a larger copper pipe hammered flat instead of #4 wire). #4 copper wire will still be used for bonding the ground rods together.

Also will use a Polyphaser AC protector for station equipment and whole house AC protector at the panel.

AB3CX, I am not sure what you are referring to, but in IMHO, my approach will provide more than adequate lightning protection.

Doug
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