Installing new antenna - Grounding question

[Rastaman147]

Hi All,

My ST2 antenna just arrived from Solid Signal today, and I'm ready to install it, but the instructions I got from the tech at Solid Signal are different from the instructions that came with the antenna.

The instructions that came with the antenna say to connect the cable to a grounding block at the point where the cable enters the house. This point will be about 25 feet from the center of the antenna. This point is also approximately 25 feet from the point in my house where I will be attaching the cable to my scanner.

I described this to the tech at Solid Signal, asking if I should be using 2 lengths of cable, each 25 feet. He said No, use this grounding block (pictured below), screw the grounding block into the antenna mast (mast is 1" diameter) approximately 3 feet from the antenna, connect the grounding block to the antenna with a 3 foot lenth of cable, then run the 50 foot cable from the other end of the grounding block down the mast, then into my house to the place it will be attached to the scanner.

I think both the instructions and tech I spoke to are assuming a certain level of knowledge / experience with antenna installation, and I'm guessing that both are leaving out steps that would be obvious to someone with experience, but it's not obvious to me.

1. How am I supposed to attach this grounding block to the mast? It comes with wood screws, which tells me it should be attached to my house like the ST2 instructions say. But if I were to drill 2 holes in my mast and bolt the grounding block to the mast vertically, the coax connectors would be horizontal. It seems to me that if I am connecting 2 lengths of cable running down my mast, I would want the coax connectors on the grounding block (and the cables) to be vertical.

2. If I mount the grounding block to my house, how do I ground it? I'm assuming the hole to the side with the set screw is for a ground wire, but what kind of wire do I need, and what do I connect it to?

Mounting the grounding block to the mast near the antenna would be my preferred way to go, since I have the proper cables on hand now.

Also, I was not able to get a clear explanation on the purpose of this grounding block from Solid Signal. Is it a safety ground or an RF ground? (the tech said "both") By being mounted to the mast, the antenna should already be grounded for lightning, right?

Would be grateful if someone could put me on a clear path so I can understand what I need to do to install this antenna the right way.

 

[prcguy]

The Solid Signal guy gave you info that is not consistent with NEC code. Look up NEC article 810 and it will give you the legal and minimum requirements for grounding your antenna.
prcguy

 

[N2JDS]

I have ST-2 too

The way I did mine was, I ran the coax from antenna, to where it would enter my home. At that point, I have an 8 foot ground rod in the dirt, a little away from the home. It comes with a clamp to attach a ground cable to that ground rod. Then, indeed attach the ground block to your house using the wood screws, but attach the ground wire in the hole with that phillips head screw. Then attach the end of coax going into your home from there. These are designed so you can use any 75 ohm coax, which is acceptable on a receive only system. For entry to the home, I used a device like this http://images.lowes.com/product/converted/034481/034481065487.jpg check Lowes for CARLON 2-1/2-in PVC Transition Item #: 73008 | Model #: E986K-CAR

A pipe goes into home, and the other pipe extends downward. Makes a nice clean entry into home, with room for expansion in the future, and then I stuff with insulation.

 

[benbenrf]

Hi All,

My ST2 antenna just arrived from Solid Signal today, and I'm ready to install it, but the instructions I got from the tech at Solid Signal are different from the instructions that came with the antenna.

The instructions that came with the antenna say to connect the cable to a grounding block at the point where the cable enters the house. This point will be about 25 feet from the center of the antenna. This point is also approximately 25 feet from the point in my house where I will be attaching the cable to my scanner.

I described this to the tech at Solid Signal, asking if I should be using 2 lengths of cable, each 25 feet. He said No, use this grounding block (pictured below), screw the grounding block into the antenna mast (mast is 1" diameter) approximately 3 feet from the antenna, connect the grounding block to the antenna with a 3 foot lenth of cable, then run the 50 foot cable from the other end of the grounding block down the mast, then into my house to the place it will be attached to the scanner.

I think both the instructions and tech I spoke to are assuming a certain level of knowledge / experience with antenna installation, and I'm guessing that both are leaving out steps that would be obvious to someone with experience, but it's not obvious to me.

1. How am I supposed to attach this grounding block to the mast? It comes with wood screws, which tells me it should be attached to my house like the ST2 instructions say. But if I were to drill 2 holes in my mast and bolt the grounding block to the mast vertically, the coax connectors would be horizontal. It seems to me that if I am connecting 2 lengths of cable running down my mast, I would want the coax connectors on the grounding block (and the cables) to be vertical.

2. If I mount the grounding block to my house, how do I ground it? I'm assuming the hole to the side with the set screw is for a ground wire, but what kind of wire do I need, and what do I connect it to?

Mounting the grounding block to the mast near the antenna would be my preferred way to go, since I have the proper cables on hand now.

Also, I was not able to get a clear explanation on the purpose of this grounding block from Solid Signal. Is it a safety ground or an RF ground? (the tech said "both") By being mounted to the mast, the antenna should already be grounded for lightning, right?

Would be grateful if someone could put me on a clear path so I can understand what I need to do to install this antenna the right way.

Rastaman

You want to get that grounding block as close to the antenna as you practically can - the less length of outer braid that any lightening strike has to travel through the better. Then you want to run the thickest wire you can afford from the grounding block screw terminal to ground, at which point stick into the ground the widest diameter piece of steel tube/re-bar whatever you can get your hands on, and stick it into the ground as deep as you can .... then hope like hell you are lucky!.

The truth of the matter regards all lightening standards is that lightening voltages and currents are so variable that you really cannot garuntee anything. You may experience a lightening strike that does no more than leave a slight black mark on the steel work of your antenna, or, you may experience a lightening strike that totally vapourises your antenna, grounding block and antenna mast.

A good bunch of principals to follow are these:

- the shorter the path the lightening has to take through any grounding to ground, the better.

- and, the larger the diameters of conductors/thicker the cable/bigger the grounding rods, used for grounding, the better.

- and, the deeper a grounding rod is pushed into the ground the better.

2 more practical points:

- the grounding block/screw terminal: cover it afterwards with self vulcanizing tape or silicone compound. This will limit rust/oxidisation building up around the screw/cable interface which acts as a resistor to any current flow. And do the same the same when connecting whatever cable you use to connect to the grounding rod, do your best to make sure no rust can build up around that connection/interface as well.

 

[prcguy]

2 more opinions and so far none would meet NEC code. Why is everyone making recommendations that are not at least to code? You might as well tell the guy to run garden hose for his natural gas line.
prcguy

 

[GKolo]

I would have gave you a ST-2 I threw a like new one away when i moved.

 

[SCPD]

2 more opinions and so far none would meet NEC code. Why is everyone making recommendations that are not at least to code? You might as well tell the guy to run garden hose for his natural gas line.
prcguy

Absolutely.

To the OP - go straight to the source.

Copy of the code is available at the Bosler Memorial Library in Carlisle

Couple of other articles on NEC 810...

Installing radio and TV antenna systems | Code Basics content from Electrical Construction and Maintenance (EC and M) Magazine

NEC Grounding- DIRECTV DISH Network HughesNet Wildblue

 

[W2NJS]

Short of a full broadcast station grounding setup, which you and I probably would never do for a scanner or even ham station, the purpose of your grounding the feedline is to allow static electricity buildup on your system to be "drained" off the feedline, and thus be less likely to be hit by lightning. If lightning does strike your setup, odds are that your equipment will be zapped into oblivion and you'll have to buy new equipment. I would follow the NEC as much as possible, and if I were home during a storm I would disconnect the antenna from the radio, which is probably the safest way to approach the problem.

 

[prcguy]

The main reason for grounding is electrical safety, placing the antenna and feedline at the same ground potential as the building electrical system. Secondary is lightning, which I agree you probably can't protect for unless the building and electrical system are designed from the ground up for surviving a direct lightning hit.

On the electrical safety issue, when I was a kid and living at home my antenna system was at the complete opposite side of the house from the AC power entry point and breaker box. I had a ground rod at the base of my 40ft mast and it turns out my neighbors electrical entry point and breaker box was closer to my antenna and ground rod than my own.

I believe my neighbor was on a different leg of the neighborhood power system because when I disconnected the coax from my radios I would get a nasty jolt and I measured 90 volts AC between my antenna ground and my house electrical ground. I assume either my neighbors ground potential was much different than mine or my house at the time had an electrical problem.

That's one reason to ground your antenna to NEC code which states something like any ground rod attached to an antenna mast, etc, must be bonded to the house electrical system with no smaller than #6 copper wire and there is a distance limit on that. NEC is very specific and for a good reason, so please refer to that first then add other suggestions afterward as long as they do not detract from code.
prcguy

Short of a full broadcast station grounding setup, which you and I probably would never do for a scanner or even ham station, the purpose of your grounding the feedline is to allow static electricity buildup on your system to be "drained" off the feedline, and thus be less likely to be hit by lightning. If lightning does strike your setup, odds are that your equipment will be zapped into oblivion and you'll have to buy new equipment. I would follow the NEC as much as possible, and if I were home during a storm I would disconnect the antenna from the radio, which is probably the safest way to approach the problem.

 

[Thayne]

The main reason for grounding is electrical safety, placing the antenna and feedline at the same ground potential as the building electrical system. Secondary is lightning, which I agree you probably can't protect for unless the building and electrical system are designed from the ground up for surviving a direct lightning hit.

On the electrical safety issue, when I was a kid and living at home my antenna system was at the complete opposite side of the house from the AC power entry point and breaker box. I had a ground rod at the base of my 40ft mast and it turns out my neighbors electrical entry point and breaker box was closer to my antenna and ground rod than my own.

I believe my neighbor was on a different leg of the neighborhood power system because when I disconnected the coax from my radios I would get a nasty jolt and I measured 90 volts AC between my antenna ground and my house electrical ground. I assume either my neighbors ground potential was much different than mine or my house at the time had an electrical problem.

That's one reason to ground your antenna to NEC code which states something like any ground rod attached to an antenna mast, etc, must be bonded to the house electrical system with no smaller than #6 copper wire and there is a distance limit on that. NEC is very specific and for a good reason, so please refer to that first then add other suggestions afterward as long as they do not detract from code.
prcguy

What you experienced with your neighbor's ground was probably caused by poor or no connection between his power feed neutral conductor which {should} be grounded at the pole & also at the house service, but sometimes those Hypress crimp connectors get loose, or perhaps the grounding electrode at the house (either water pipe-ground rod or both) was not connected to the neutral properly.

A few years back a plumber was electrocuted in a crawl space when he cut a 1/2" copper water pipe which was where all the neutral current was flowing because the other grounds had no continuity. Ground rods are really not very good except for lightning--thats why the code requires 2 rods electrically connected with #6 CU six feet apart unless you can prove 1 rod is 25 ohms or less to ground.

PS I really admire your antenna expertise!)

 

[prcguy]

As a side note, when I was young and lived with my parents I had a lot of CB stuff and used it to communicate with friends in town. The FCC had monitored me talking for some length of time without giving my FCC callsign, which was required in the 1970s.

Two FCC field engineers came to my house to "inspect" the radio I was using on the day of the violation and in the haste I pointed to the least modified radio I had which was plugged into 110v and wired to the antenna with the ground problem. When the field engineer disconnected my antenna to connect his Bird wattmeter with internal load he was shocked pretty bad and nearly dropped his meter on the floor.

The FCC guys initially said I my violation would probably not result in a monetary forfeiture but a few weeks later came the pink notice. I always wondered if shocking the FCC field engineer had anything to do with the ultimate outcome of that adventure.

Thanks for the kind words.
prcguy

What you experienced with your neighbor's ground was probably caused by poor or no connection between his power feed neutral conductor which {should} be grounded at the pole & also at the house service, but sometimes those Hypress crimp connectors get loose, or perhaps the grounding electrode at the house (either water pipe-ground rod or both) was not connected to the neutral properly.

A few years back a plumber was electrocuted in a crawl space when he cut a 1/2" copper water pipe which was where all the neutral current was flowing because the other grounds had no continuity. Ground rods are really not very good except for lightning--thats why the code requires 2 rods electrically connected with #6 CU six feet apart unless you can prove 1 rod is 25 ohms or less to ground.

PS I really admire your antenna expertise!)

 

[Rastaman147]

I now have the coax grounded to my water pipes. I tested it briefly in the basement, using a 3 foot section of cable and it seems to be pulling in more stuff than the rubber duck. Now I just need to run the last section of coax upstairs to connect to the scanner and I'll be in business. Thank you all for your input!