Grounding dishes/antennas

[pedrogarcia]

Whilst the codes are clear http://www.satelliteguys.us/free-ai...s-your-switchbox-look-like-5.html#post2062603 they appear to have been written for Cband, DN annd DTV where the dish itself has a direct connection to the coax shield.
However with FTA where this is rarely the case, as LNBs and their holders are plastic. I think the European method of additionally grounding the dishes themselves locally to be more appropriate. Since there is then no ground connection to the house ground there would be no ground looping involved.
Actually the idea of the coax doubling as part of the lightning conductor route is a alien to me.
Perhaps like European codes this is covered in another unrelated chapter.

 

[zamar23]

Interesting observation. Can you add this post to the related thread above to make it easier to find in one place for everyone? Adding a link to the Standard mentioned and/or explanatory pics would help to visualize the solution.

 

[pedrogarcia]

Zamar . Have done

 

[guapoharry]

I read the first post over and over. Does it suggest to install a separate grounding rod connected only to the dishes? (OK ostensibly because the LNBFs have plastic housings.) If so, that doesn't sound correct.

Why not consider the text assocaited with those grounding diagrams in Zamar's post? See Grounding Satellite Dish and Lead-In Cables The way I read that is the dish (not pictured) is mounted to the pole (which is grounded as pictured).

As I understand it, all of the grounding should be bonded to the building ground. If you wanted to install another ground rod, (out by the dish, say...) it would have to be bonded together to the rest of it with a 6 AWG conductor per code...

You can read the code online for free. (Free registration required) It's kind of esoteric, so good luck without someone like that Mike Holt guy to explain...

The Electrical Code is NFPA70.

EDIT:

Here's something else to consider...

Grounding your satellite dish and system

 

[pedrogarcia]

I think you may have missed the point. The code is fine for electrical grounding, and where such antennas are close to the house ground.
DN and DTV coax with its messenger grounded coax I believe does not meet the code on ground cross section.
FTA dishes themselves are not normally grounded by this method. FTA Dishes especially remote mounted are probably the best lightning attraction and as such should be grounded locally for such strikes to code cross section or better. The plastic just gives insulation against ground loop impedance via the coax, and this should still be gound bonded per code.
The point I am trying to convey is that coax alone is in no way a dish grounding conductor. Taking a lightning conductor back to the house is not good practise.
Not all ground mounted antennas have sufficiently low ground impedance in themselves.

 

[Wescopc]

The code calls for the Mast to be grounded by a 17 gauge Steel wire (messenger wire) this ground is NOT for lightning protection. but for static electricity that might build a charge on the mast. None of the code requirements will protect against/from a direct hit. The coax is grounded near the house to protect against an induced current from a strike nearby. If you have a separate ground, then it must be bonded to the house ground (with a number 6 or larger copper wire) to keep the induced voltage potential nearly the same at both grounds for safety.
As a side note, the code does not require grounding the dish - only the mast. So strictly speaking, if the mast was plastic - no ground would be needed. In the real world the mast is metal and sometimes the dish is plastic, so a static ground would be required.
Cheers
Bob

 

[guapoharry]

Yes I did miss the point. That sounds reasonable, Pedro.

While looking at the datasheet for RG6 messenger coax, it listed the messenger as

GROUND:
Static Ground BCCS - Bare Copper Covered Steel
Static Ground Diameter 0.045 in.

This places it at "17" AWG, which as you state is inadequate for electrical grounding, hence the "static ground" designation, apparently.

What I have seen in the code defines boundaries in terms of a dwelling. So, if you have a dish out in the yard, at some point it starts looking more like a distribution system example.

I follow the example of FTA LNBFs and holders being insulated, there would be no ground loop and that it would best to ground the dish locally.

But then, a C-band dish example where the dish, scalar ring, feed and LNB commonly are all metallic comes to mind. (as a pathological example perhaps by comparison... ) In that example the parts are not exactly bonded together, but the insulation would appear to be minimal... How would one handle that situation?

 

[pendragon]

The last time I read the code, it seemed a little ambiguous on this issue. From what I recollect the entire emphasis was on safety grounding from a power perspective. The issue of lightning was all but over-looked.

In the end for each of my dishes planted in the ground, I drove in a local ground rod, bonded it to the dish and to a conductor that runs in the conduit back to the building ground. This was pretty simple because all my coax runs within a few feet of the electrical service entrance. For the dishes on the roof, I ran ground conductors with the coax back to the service entrance. In all but one case, this is the shortest path to any ground.

I'm required to pull a permit for planted dishes, but not for anything on the roof. This doesn't make a lot of sense to me, but it means the roof is my preferred installation point when practical. Originally I was a little concerned about the inspections with respect to grounding for the planted dishes, but this never came up.

 

[ZetaMale]

Whilst the codes are clear http://www.satelliteguys.us/free-ai...s-your-switchbox-look-like-5.html#post2062603 they appear to have been written for Cband, DN annd DTV where the dish itself has a direct connection to the coax shield.
However with FTA where this is rarely the case, as LNBs and their holders are plastic. I think the European method of additionally grounding the dishes themselves locally to be more appropriate. Since there is then no ground connection to the house ground there would be no ground looping involved.
Actually the idea of the coax doubling as part of the lightning conductor route is a alien to me.
Perhaps like European codes this is covered in another unrelated chapter.

I've always considered it to be a good idea to ground the antenna to it's own ground rod. If I recall correctly, this is required in a lot of local codes. I have my TV antenna tower and my ham radio tower grounded, also. I work with terrestrial microwave radio and Ku sat up/down links, also, and all of our towers and fixed satellite antennas are grounded including any guy wires. I highly recommend grounding antennas - it might just save your electronics from a nearby lightning strike (rarely does anything survive a direct lightning strike, though). There are coax surge suppressors that would help also.

 

[pedrogarcia]

This all started when I realigned a dish that actually had a plastic mount on to its pole clamp. I took this up with Mike Holt and he and his collegue replied to the effect the code needs amendments and they will work on this.
Pendragon it seems the code is for static discharge as opposed to lightning. Remote grounding , shortest path is definately the way to go and personally I would not take a ground back to the service ground to prevent ground loop impedance.
In Cyprus we do have lightning storms without any rain so a good local ground is important. When I can find the secure place I put the photo of a aluminum 3m dish hit by lightning Iwill post it.

 

[pendragon]

Pendragon it seems the code is for static discharge as opposed to lightning. Remote grounding , shortest path is definately the way to go and personally I would not take a ground back to the service ground to prevent ground loop impedance.

I don't think the code cares much about static discharge. It seems mostly concerned with ensuring the mains ground is consistent.

When I was in college I worked as a chief engineer at several broadcast facilities, and separately ran a large sound reinforcement company. It was interesting to see how different the perspectives were with grounding. In RF everything was grounded everywhere and separately bonded together, although the latter not always that well. It was very safe, but there were ground loops everywhere and this was a constant source of audio/video problems.

In sound reinforcement, whether indoors or out, the name of the game was to have one hard ground to which everything had one path to minimize mains noise. But during outdoor festivals it was easy to have a system spread out well over a 100m diameter and talent/crowd safety was a major concern. Things are a little different today, but back then one could have dozens of µV-level microphone lines running from the stage back to the mixing desk alongside speaker amps pushing 100-200V on their outputs. With that much system gain it seemed amazing that anything worked at all.

This school of hard knocks taught me a lot. For safety's sake I had to live with multiple localized grounds. For ground-loop sake, I needed to minimize return paths and ensure the bonding between the local grounds was overwhelmingly low in impedance. It was a lot of extra work, but in time I cleaned up the broadcast facilities and got the sound reinforcement methodology tuned to the point that mains noise was inaudible directly at the main speaker stacks. Grounding often looks like magic, but really is just meticulous engineering.

 

[Wescopc]

I don't think the code cares much about static discharge. It seems mostly concerned with ensuring the mains ground is consistent.

However the 17 gauge steel messenger wire requirement is in the code and seems to be only for static discharge. It certainly would not be big enough for safety.
Bob

 

[zamar23]

When I was in college I worked as a chief engineer at several broadcast facilities, and separately ran a large sound reinforcement company.

When I was in college, I participated in a small times research project that actually provided a good grounding in my future profession.