[TowerTalk] bonding to AC power box or inside fuse panel?

[Dick Green WC1M]

Glad you put it that way, Jim. I think the term "single point" has confused a lot of hams. The essential thing, as you say, is to make sure all the grounds are bonded together by the shortest practical path.

I think what most people like to call a "single point" ground is the station ground on the outside of the house to which all the station equipment, cables and tower ground system are bonded. It's usually convenient and practical to bond all these things together in one place as they enter the house. But that ground point must never stand alone -- it must be bonded to any and all of the other ground systems you have.

There's no reason why a station can't have more than one grounding point for equipment chassis and cable grounding. In fact, many do: one might be a set of ground rods tied to a common point at the tower for cables, switches, lightning suppressors, metal equipment cabinet, the tower itself, the Ufer ground, etc., and another set of ground rods at the house tied to a common point for chassis grounding, cable grounding, lightning suppressors, switches, equipment cabinets, etc. But the two ground systems must be bonded together, and they must be bonded to all the other ground systems in your house: AC, telco, cable, satellite, etc., etc.

Some grounding decisions are not straightforward. For example, my AC and telco services are on one side of the house and the station "single-point" ground is on the other side of the house. It would have taken 150 feet of low-inductance wire and at least 10 8-foot ground rods and Cadweld shots to connect the ground systems outside the house. So I decided to bond them together inside the house, using about 25 feet of 1/0 wire. Not the recommended way to do it, but it my opinion a better way to ensure that the ground systems are at the same potential.

Another example is bonding the tower ground to the single-point ground at the house. My first tower farm is 265' from the house. Being new to tower construction, I laid 265 feet of 1/0 ground wire in the trench running between the two locations in order to bond the ground systems. This was not cheap, to say the least (though it was before the big run up in copper prices.) Later, I read an article by Polyphaser that said if the ground systems are more than 75' apart it does no good to bond them -- the wire inductance will be too high to make an effective connection. With this in mind, when I installed my second tower system in a different location 220' from the house, I did not run a separate ground wire. The Polyphaser argument made sense to me. Also, there are two runs of 1-5/8" hardline in the trench, and the gigantic copper shields on those babies surely provide a lower inductance path between the tower and house than a 1/0 wire would -- if, in fact, any wire has low enough inductance at that length to be effective.

73, Dick WC1M

> -----Original Message-----
> From: Jim Brown [mailto:jim at audiosystemsgroup.com]
> Sent: Monday, January 21, 2013 7:24 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] bonding to AC power box or inside fuse panel?
> 
> On 1/21/2013 2:51 PM, Jeff Blaine wrote:
> > What’s the best way to effect a single point ground in this
> combination?
> 
> Stop worrying about "single point" and simply bond EVERYTHING together
> by the shortest practical path. In the power entrance panel for ANY
> premises, earth must be bonded to the enclosure itself, and there must
> be a bond between neutral and that enclosure.  By EVERYTHING I mean
> everything in your home that is grounded, including CATV entrance, Telco
> entrance, power entrance, your antenna entrance, your shack operating
> desk, structural steel if there is any, cold water (if it's metallic),
> lightning protection, etc.
> 
> In general, you can have as many earth connections as you like, they can
> be anywhere you like, but they MUST all be bonded together. Anything NOT
> bonded is unsafe.
> 
> 73,