[SJRA-Members] Roof Mount Tower Install. Instrs.: Would you add or change anything?

[Bob Beyer]

Yep.  Like I said… Grounding can get complicated.

 

I did not suggest you ground the antenna to the independent ground rod, but rather the tower and mast.

Some people advocate for “DC grounded” antennas.  An antenna that followed this practice would have one side of its driven element(s) attached to earth and thereby then also the tower and mast.

While asking about the tower and mast, you said:  “Did you ground it to its own ground stake or to your house's main ground?”
You didn’t mention in your original message that you already had an RF ground copper bus bar in shack already and that it was tied to the house.

 

I don’t know if this will help at all or not but I will give you a description of something related.

For a long time, my job involved managing a satellite network with several hundred downlink sites.

We have dish antennas installed on commercial buildings all over the U.S.

When we install a new site, the coax from the antenna runs through at least one ground block attached to the antenna mount, preferably two.  This ties the shield of the coax to the mast.

The mount is then connected back to “building steel” at the nearest possible point with a heavy gauge copper wire.

The electricians provide this ground point and bring it out to the antenna mount.  Our techs just attach it to the antenna mount.

The goal here is to have the mount connect to a heavy, nearby “earth” ground as close to the mount as possible.

In the event of a strike, our desire is to have the charge head for the nearest ground first.

However, not to be entirely reliant on this, once the coax is inside the equipment room where the receiver is, the coax once again passes through a ground block on the Master Ground Bus Bar in the equipment room.

This is a separate heavy duty ground that is established in the equipment room for all the electronics to be grounded to.

As I understand it, this is supposed to be tied to the same ground that the electrical system references (probably also “building steel”) but it is not run via the electrical panels.

 

If you already have some grounding established and it’s tied to the house’s electrical ground, things get more complicated.

 

Below is a link to a video of the talk that Ward Silver, N0AX, gave at Contest University in 2017.

Ward is the one who wrote the book I mentioned.

He will probably say some things that contradict what I’ve said. You should take his advice over mine.

 

https://www.youtube.com/watch?v=4RkiRwjK2oU

 

GL,

Bob – KE2D

 

From: John Jones [mailto:jdjones3109 at gmail.com] 
Sent: Wednesday, May 06, 2020 10:58 PM
To: Bob Beyer; sjra-members at mailman.qth.net
Subject: Re: [SJRA-Members] Roof Mount Tower Install. Instrs.: Would you add or change anything?

 

Thanks Bob. I have received SO much conflicting information about this subject. My shack's RF ground is a copper bus bar that's attached to the house ground and my end fed antenna's ground wire is attached to it too. I was told that they HAD to be attached to it in order to be in compliance. When it comes to grounding, you can ask two people and get three different opinions. Ugh!  I wonder if the Construction Office issuing the permit is going to require that I use a licensed electrician to do the ground and get it inspected. I'll see. If not, I suspect that I'll add a ground rod like you suggest and ground the antenna to it. My house ground is in a location where's it's surrounded by my patio, driveway, and walkway so it would be really hard to link this new ground rod to it. Hard and expensive. 

 

On Wed, May 6, 2020 at 10:49 PM Bob Beyer <bob_beyer at verizon.net> wrote:

Hi John,

Grounding can get complicated and a well thought-out, comprehensive ground system would ultimately "bond" a house's electrical ground to an overall ground plan (that's plan, not plane).
Among other things, this would include a number of distributed ground rods exothermically welded to a specific kind of heavy copper cable running around the house in a continuous ring and buried beneath the surface of the ground.

However, if you're just going to do single point grounding of the tower and mast and not setup a comprehensive ground system, I would by no means recommend you connect it directly to your home's electrical panel.
That would effectively be like extending a lightning rod from your electrical panel to the a point at least 6 ft. above your roof.  "Hit me! Hit me!"

Years ago I had a ham friend who was a licensed electrician.  In addition to many commercial and residential jobs, he worked on the installation of the Tokomak Reactor at Princeton Plasma Physics.
One day his 75' crank-up tower was struck by lightning and it burned out his submersible well pump.  He said that in his experience, most lightning damage he saw "came in on the ground" of the electrical system.
While this seems counter intuitive, it actually does occur.  As I understand it, a lightning strike can momentarily elevate the potential of a home ground to a voltage potential greater than the potential of the AC mains feed into the home (typically 240 VAC).  At that instant, flow from the energized ground can occur back toward the AC power lines by passing through any electronics, appliances, lights, etc. in circuit.  Putting a lightning rod on your roof and connecting it to your electrical panel would be an ideal way to create the potential for this to occur as I see it.

Also, the electrical code may not allow this kind of ground connection either but I am not certain of that.

Unless you are going to setup a complete grounding system now (time consuming and expensive), I suggest that you drive one or more ground rods into the ground and connect the mast and antenna to them with the heaviest gauge wire you can afford. Something like No. 4 or even larger. 

If you want to learn more about good grounding practices, there is an ARRL publication written by Ward Silver, N0AX, called "Grounding and Bonding for the Radio Amateur".  Amazon carries both the paperback and Kindle versions.

If there are electricians in the audience or those with more experience and expertise than me, I am happy to be corrected on any of this.

Bob - KE2D


-----Original Message-----
From: sjra-members-bounces at mailman.qth.net [mailto:sjra-members-bounces at mailman.qth.net] On Behalf Of John Jones
Sent: Wednesday, May 06, 2020 10:05 PM
To: sjra-members at mailman.qth.net
Subject: [SJRA-Members] Roof Mount Tower Install. Instrs.: Would you add or change anything?

Thank you everyone for your advice. I purchased the K4KIO Hex Beam Antenna with all six bands (20 - 6), ice cords, snap on balun, and universal clamp
for masts 1.25" - 2.5".   https://www.k4kio.com/

I'm mounting it on a W8IO Roof Tower (Model IO-45) and a 1.9" OD x 0.150"
wall x 72" length 6061-T6 aluminum mast.  Please see *Page 5* of the attached installation instructions and give me your thoughts. If anyone has a roof tower like this one, I'd love to hear your grounding recommendations. Did you ground it to its own ground stake or to your house's main ground?
http://www.w8io.com/rooftower.htm

*NOTE: The antenna, roof tower, and mast have already been purchased so there's no need to recommend alternatives. *