HF, VHF, UHF, and Grounding

[K8KPO]

(Yes, I always use the Oxford comma)

OK, so I'm taking a step back to clear my head concerning my HF issues and am moving on to something else for a moment, although my questions really apply to all ham frequencies. I apologize in advance for the length of this post.

There is an astounding amount of information out there about antenna grounding. Unfortunately, a lot of it assumes a certain level of knowledge that not every person has, and even worse it appears that a good amount of it is contradictory, at least to my untrained eye. So my comments and questions may seem a bit overly specific or pedantic, but it's because I'm trying to make sure I understand exactly what you're saying.

First off, a little background just to set the stage. My house is over 100 years old. My radio equipment is in the computer room on the second floor. It may move to the basement some day if I finish a portion of it as I would like to do, but that's a couple years away. Almost all of the first floor has been converted to romex wiring, but the entirety of the upstairs is still knob and tube. As a result, nothing on the second floor has a ground, although all outlets are 3 prong type. I knew this at the time we bought the house. I'm going to completely rewire the second floor, however it's not happening this year. I'm going to be having back surgery in August, and it would just be too much for me to crawl around rewiring the upstairs until my back is better. So for now, I have what I have. Additionally, I may have to be off work for a few weeks after my surgery which is why I want to do a few of these upgrades to my radio now so that I'll have something to play with if I'm stuck at home for awhile. So please bear in mind that the second floor will have proper electrical wiring at some point (hopefully next spring/summer), but it's just not happening right now. Ok, that's out of the way.

I have a little 1/4 wave 2m ground plane antenna in my attic that I built when I first got my technician license years ago. It actually has worked better than I expected, but I want to reach and hear further than I can right now. Since the current 2m antenna is in my attic I have been unconcerned about any type of grounding. I've bought an antenna that I'm going to be mounting on my roof which should be a substantial upgrade. It is approximately 17 feet in height (the antenna alone, it will obviously be higher than that to the tip once I have it installed). I'm concerned about grounding issues for this, for my equipment, and for any HF antenna that I put up in the future. In case it matters, I currently have a G5RV Jr (obviously not for VHF/UHF) running from my house to a pole in the backyard. It is unremarkable and lacking in performance. It is not grounded in any way.

There is a window in the computer/radio room and it is almost directly above the electrical grounding rod for the house.

My first round of questions are as follows:

(1) I'm sure that I should ground the mast that my new VHF/UHF antenna will be mounted on. Does it matter where on the mast I connect the ground wire? Does it matter if the connection point to the mast is closer to the bottom (near the roof) or closer to the top (near the antenna connection point)?

(2) Should the coax between the VHF/UHF antenna and my radio have a lightning arrester in it somewhere? If so, does it matter where in the line it is?

(3) Do I need to separately connect the shield of the coax coming from the VHF/UHF antenna to the ground rod? If so, can it be connected to the household electrical ground rod or do I need to add another rod and then bind it to the existing one?

(4) Should there be a separate ground wire running from one of the ground rods into my radio room and then connecting to my radio equipment in the room?

(5) I'd like to make some type of a window/coax feed-through. I'd probably cut a 2x4 to fit the width of the window, and then drill and install coax connectors in the 2x4 as well as a ground (maybe using a short piece of all-thread) so that I can terminate the ground wire and coax on the outside, then jumper everything on the inside. I'm hoping that makes sense. Is this an ok idea? If so, what type of coax connectors are good for this?

If you stuck with me this long I appreciate it. I will have more questions after these issues are resolved.

 

[prcguy]

Are you grounding for lightning protection, RFI or human safety? I'll weed out a few for you. I believe its impossible to do anything to your house or wiring or antenna mast that would survive a direct lightning hit, its just not possible without rebuilding your house.

There is also little you can do for RFI and grounding with a radio room on the second floor. All other grounding questions for human safety can be answered by the National Electrical Code, article 810, which deals specifically with grounding antennas and radios. Here is one example that might help: https://www.mikeholt.com/download.php?file=PDF/Radio_and_Television_2014NEC.pdf

 

[K8KPO]

I know that it is impossible to prevent a lightning strike. My goals are for mainly two things. First, in my mind it seems logical that if I keep my antenna and mast at the same ground potential as the dirt underneath me then it makes my stuff no more appealing to the bolts of electric in the sky than anything else around, which hopefully makes it no more likely to get struck than anything else in the neighborhood around me, which is the best I can hope for. My second goal is about performance and the (vain?) hope that grounding the antenna and equipment inside will help keep out some noise (mostly in the case of HF when I decide I'm ready to start beating my head on that again).

Or maybe I'm just delusional, which is a distinct possibility.

 

[W5lz]

There are some 'givens' with grounding, they tend to make sense when you think about it. The National Electrical Code (NEC) is a very good source of information about electrical and RF grounding... they are NOT the same things at all.
The questions asked:
1.Where? On the part closest to ground/dirt. That mast/pole/whatever will typically be a better conductor than a wire. So, why not use it?
2.Certainly wouldn't hurt! And like that mast, where it's closest to ground/dirt.
3.The shield of the feed line should be connected to ground. If there are more than one, then there will be more than one connection.
This is starting into the 'complicated' part of grounding.
A ground system for your antennas and radios should all be connected to the 'house' common ground. Separate ground rods for each is NOT a good idea (unless you connect all those ground rods to the house's common ground point). If there are separate ground rods for everything then there can be a potential difference (voltage) between those ground rods and that ain't good. Every thing should be at the same potential (voltage) at ground. Thats a difficult thing to do after a house is built. Not impossible in most cases, just difficult. An example of such a ground system is a LARGE conductor starting at the houses service ground running completely around the house (underground) and ending at the service ground again. See where that might be difficult after the driveway, side walks, etc, is poured? That's the -best- way, but naturally very few people ever do that (me either). That sort of covers #4.
5.Yes, an entry like you describe is a good way of doing it. Given the typical width of a window, you can get quite a few lines in that way.

This is NOT the best explanation of station grounding! There are certainly better, and more comprehensive ones out there. I very much recommend you read as much as you can find about grounding, and especially that NEC.

 

[K8KPO]

And should I assume from your lack of answering that putting a lightning arrester inline with the coax is a waste and that grounding the shield of the coax is also a waste?

 

[JoshuaHufford]

I run a Polyphaser surge protector on all of my antennas. I know this will not do anything for a direct strike, but I'm hopeful that it can help for nearby strikes. I have a setup located away from my home that runs 24/7 and so far have not had any components damaged, which include 4 radios and a preamp, all after the Polyphaser connected to the ground rod of the electrical supply.

I have had a few temporary setups here at home as well and I can tell there is less noise and decode signals better when the shield is connected to ground via the Polyphaser. It isn't a huge difference but enough to just notice. So I think it is worth it for what my opinion is worth.

 

[iMONITOR]

I really think some attempts at grounding actually attract lightning!

 

[prcguy]

Its good practice to install a lightning arrestor on all feedlines before they enter the house, especially for HF antennas. A nearby lightning strike can induce lots of voltage on antennas and the more metal or wire hanging out there the more voltage they can pick up. A lightning arrestor can shunt the induced voltage to ground and possibly protect a radio down stream. They also make a handy place to attach a ground wire.

I've lost at least two HF auto tuners to nearby lightning strikes where I had 100ft of horizontal wire attached and the closest strike I know of to my antennas was about 1 city block away. I lost a third auto tuner on a 43ft vertical at a different site and I presume also from a nearby strike.

And should I assume from your lack of answering that putting a lightning arrester inline with the coax is a waste and that grounding the shield of the coax is also a waste?

 

[jim202]

Let me say this up front. If you ask a question about grounding and you ask this of 10 people, you will probably get 10 different answers.

My background has been in the public safety and cellular construction field for many years. I still learn new things all the time. But grounding is an art and a science. There are a couple of guides to look at and learn what they are trying to tell you. Each installation is different in that the soil conditions will cause you to modify how you make a grounding SYSTEM. Yes, it is a system and takes multiple items together to make it work correctly.

One of the old tails that just won't go away is the comments you will have people keep telling you. That is you can't survive a direct lightning strike. This is an old tail that is so un true. If that was the case, every radio and TV station could not afford to keep repairing damage from every storm that goes through. The same is true of every cellular tower around the country. Think about all the public safety towers around the country. They also have to stay operational, regardless what the weather is.

With that said, I would start trying to learn some basics in the NEC (National Electrical Code). You don't have to go into depth for everything in it. But focus on the grounding and telecommunications section.

Another very good document is put out by Motorola. It is called the "R56 Standard". If you look around the Internet enough, you should find a place where you can download it for free. This is the bible that most commercial radio installations follow. Even the grounding standards for each of the different cellular companies use. I have worked for several of them over the years and they generally all follow the R56 Standard.

I made a comment that you can stand a direct hit on a communications tower. I live in southern Louisiana where the ground here is either marshy or hard red clay. You might find some slightly different soil as you go further north. If your in the Florida region it's sand. I originally came from New England and many of the tower sites are built on one of the highest hill you can find. There the soil is generally solid granite rock. But anyway, I drove up to a tower site one afternoon in the middle or a rip roaring thunder storm. There was a loud boom and the ground shook a little. I looked at the tower and the legs were steaming in the heavy rain. Yup, it took a direct hit.

I waited till the storm passed and then went into the comm shelter at the base of the tower. All the cellular equipment was operating just fine. The public safety radios were working fine and there was 3 ham repeaters there. Out of the 3, 2 of them were working normally. The 3rd was dead and had this burnt smell.

Long story in the short answer, the 3rd ham repeater was not correctly grounded and did not have any surge protection on the antenna cable or on the AC power to the cabinet. I know the ham group that owned that 3rd repeater and have been trying to get them to understand the importance of having a properly installed "GROUNDING SYSTEM". They just flat refused to follow the guide lines. so now they have a dead repeater that will need to be repaired.

You may think that I am long winded. Yup I agree that I talk a bunch, but it is important for people to understand that just grounding a radio cabinet is not enough surge protection.

Old homes will generally have old ground rods. Old ground rods do not provide a good low resistance ground with age. I try to point this out to people that if they have been in that house for more that about 10 years, their electrical meter ground rod should be replaced. Ground rods are either steel that has copper plated to them or they are steel that have been galvanized. Over time both will corrode and when this happens, you loose the low resistance that you are looking for. When you do go to replace the ground rod, make sure you kill the main breaker in your electrical breaker or fuse box before removing the ground wire going to the ground rod.

One other comment I will pass along is about ground rods. A ground rod has what is called a cone of influence around it in the soil. This cone is a radius distance that is equal to half the length of the rod. So you don't want to space ground rods any closer than the cone of influence covers. In simple terms, if you have 10 foot ground rods, you space them 20 feet apart.

The connections at the ground rods are important too. I like to use an exothermic weld to connect the ground wire to the ground rods. This way I don't have to worry about corrosion causing a poor connection over time.

One other comment is the size of the ground wire to use. In public safety and cellular communication sites, the minimum wire size used is number 2 solid. Generally it is solid and plated to help reduce corrosion to the wire. There have been some tower sites that I have been to that have used much larger wire.

Hope this has provided some insight on the simple basics of tower grounding. Surge protection on your coax cables is a must. There is much more to it, but I am trying to keep this short.

Jim

 

[prcguy]

A cell site is literally designed and built from scratch from the ground up. Pun intended. They survive direct hits all the time because they are meant to. A residential house with typical AC entry is in no way designed to survive a direct hit as are any hobby or ham grade antennas or masts, etc. Yes you can make it lightning proof with a professional engineered system and massive retrofitting to the home, but at what cost? $20k? $30k? $50K? I've been lead project engineer on many huge satellite antenna installs and know what it can cost to include this type of engineering and grounding for an antenna install. Its not cheap.

I think its unrealistic to tell someone they can lightning proof their home antenna install. Can I suggest that if someone gives advice to do this or that and it will survive a direct hit, please take responsibility for all damaged equipment if they do get a direct hit and lots of stuff breaks. I'm not qualified to give specific lightning proofing advice and don't want the liability that goes with it.

Let me say this up front. If you ask a question about grounding and you ask this of 10 people, you will probably get 10 different answers.

My background has been in the public safety and cellular construction field for many years. I still learn new things all the time. But grounding is an art and a science. There are a couple of guides to look at and learn what they are trying to tell you. Each installation is different in that the soil conditions will cause you to modify how you make a grounding SYSTEM. Yes, it is a system and takes multiple items together to make it work correctly.

One of the old tails that just won't go away is the comments you will have people keep telling you. That is you can't survive a direct lightning strike. This is an old tail that is so un true. If that was the case, every radio and TV station could not afford to keep repairing damage from every storm that goes through. The same is true of every cellular tower around the country. Think about all the public safety towers around the country. They also have to stay operational, regardless what the weather is.

With that said, I would start trying to learn some basics in the NEC (National Electrical Code). You don't have to go into depth for everything in it. But focus on the grounding and telecommunications section.

Another very good document is put out by Motorola. It is called the "R56 Standard". If you look around the Internet enough, you should find a place where you can download it for free. This is the bible that most commercial radio installations follow. Even the grounding standards for each of the different cellular companies use. I have worked for several of them over the years and they generally all follow the R56 Standard.

I made a comment that you can stand a direct hit on a communications tower. I live in southern Louisiana where the ground here is either marshy or hard red clay. You might find some slightly different soil as you go further north. If your in the Florida region it's sand. I originally came from New England and many of the tower sites are built on one of the highest hill you can find. There the soil is generally solid granite rock. But anyway, I drove up to a tower site one afternoon in the middle or a rip roaring thunder storm. There was a loud boom and the ground shook a little. I looked at the tower and the legs were steaming in the heavy rain. Yup, it took a direct hit.

I waited till the storm passed and then went into the comm shelter at the base of the tower. All the cellular equipment was operating just fine. The public safety radios were working fine and there was 3 ham repeaters there. Out of the 3, 2 of them were working normally. The 3rd was dead and had this burnt smell.

Long story in the short answer, the 3rd ham repeater was not correctly grounded and did not have any surge protection on the antenna cable or on the AC power to the cabinet. I know the ham group that owned that 3rd repeater and have been trying to get them to understand the importance of having a properly installed "GROUNDING SYSTEM". They just flat refused to follow the guide lines. so now they have a dead repeater that will need to be repaired.

You may think that I am long winded. Yup I agree that I talk a bunch, but it is important for people to understand that just grounding a radio cabinet is not enough surge protection.

Old homes will generally have old ground rods. Old ground rods do not provide a good low resistance ground with age. I try to point this out to people that if they have been in that house for more that about 10 years, their electrical meter ground rod should be replaced. Ground rods are either steel that has copper plated to them or they are steel that have been galvanized. Over time both will corrode and when this happens, you loose the low resistance that you are looking for. When you do go to replace the ground rod, make sure you kill the main breaker in your electrical breaker or fuse box before removing the ground wire going to the ground rod.

One other comment I will pass along is about ground rods. A ground rod has what is called a cone of influence around it in the soil. This cone is a radius distance that is equal to half the length of the rod. So you don't want to space ground rods any closer than the cone of influence covers. In simple terms, if you have 10 foot ground rods, you space them 20 feet apart.

The connections at the ground rods are important too. I like to use an exothermic weld to connect the ground wire to the ground rods. This way I don't have to worry about corrosion causing a poor connection over time.

One other comment is the size of the ground wire to use. In public safety and cellular communication sites, the minimum wire size used is number 2 solid. Generally it is solid and plated to help reduce corrosion to the wire. There have been some tower sites that I have been to that have used much larger wire.

Hope this has provided some insight on the simple basics of tower grounding. Surge protection on your coax cables is a must. There is much more to it, but I am trying to keep this short.

Jim

 

[W5lz]

K8KPO
I would assume that if you want to be correct. Why didn't I list it? The post was getting long enough I just didn't want to go toooo long and besides I didn't think of it. You might read the last paragraph again...

 

[Lauri-CoyoteFrostbite]

This is quite an emotionally charged technical subject, as you are no doubt learning 8KPO.

Read and study all the material you can get your hands on-- and approach this scientifically.
This is advice easily given, but where to turn ?

This is my favorite place to start -

http://lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

Good Luck Cowboy !

Lauri

 

[zz0468]

I had one site that took a direct hit, and the ground rods and bonding cables ended up coated in glass. The site equipment was mostly undamaged, but the ground system had to get completely replaced. That was a $30K repair job. The original system was done correctly, as evidenced by all that survived. But there was a tremendous amount of energy in that strike. The lesson learned is, frequent inspections and measurements of ground systems to insure they're still working as designed.

 

[westom1]

Protection from a direct lightning strike is routine. So routine that damage is most often created by human mistakes.

Start with what is fundamental to protection - ground. Obvioiusly wall receptacle safety (equipment) ground is completely unrelated to the ground that does protection - earth ground. Impedance (not resistance) alone makes that obvious.

Polyphaser protectors do not do protection. No protector does. Effective protectors (ie from Polyphaser) do something useful only when connected low impedance to "single point earth ground". All four words are relevant. The reasons for each should be obvious to a ham.

Another demonstrates what has been well understood and routinely implemented even over 100 years ago:

Well I assert, from personal and broadcast experience spanning 30 years, that you can design a system that will handle *direct lightning strikes* on a routine basis. It takes some planning and careful layout, but it's not hard, nor is it overly expensive. At WXIA-TV, my other job, we take direct lightning strikes nearly every time there's a thunderstorm. Our downtime from such strikes is almost non-existant. The last time we went down from a strike, it was due to a strike on the power company's lines knocking *them* out, ...

Since my disasterous strike, I've been campaigning vigorously to educate amateurs that you *can* avoid damage from direct strikes. The belief that there's no protection from direct strike damage is *myth*. ...

The keys to effective lightning protection are surprisingly simple, and surprisingly less than obvious. Of course you *must* have a single point ground system that eliminates all ground loops. And you must present a low *impedance* path for the energy to go. That's most generally a low *inductance* path rather than just a low ohm DC path.

Digital ground, breaker box ground, virtual ground, chassis ground, water pipe ground, receptacle safety ground, floating ground, analog ground, and earth ground. All are electrically different. Protection from transients (ie lightning) is only about earth ground. And that connection must be low impedance (ie less than 10 feet, no splices, not inside metallic conduit, no sharp bends, separated from other non-grounding wires, etc).

QST Magazine has two articles that introduce this in 2002. Motorola's r-56 manual is clear about this. Mil-Std 419 is often referenced. Army's tm5-690 manual discuses same. Erico Tech Notes demonstrate this Sun Microsystems' "Planning guide for Sun Server room" discusses same in Section 6.4.7 "Lightning Protection". Ufer grounds were created just for this reason. Every telco CO must and always has this solution since those sites can suffer about 100 surges with each storm. Plenty to learn. Electronics atop the Empire State Building would suffer about 23 direct strikes annually without damage. 40 atop the old WTC. All of this based upon what Franklin demonstrated over 250 years ago.

A direct lightning strike without damage is routine. So routine that damage is considered a human mistake. And this is fundamental. Protection is only as effective as the quality of and low impedance connection to single point earth ground.

 

[MUTNAV]

These have a lot of good grounding info, as noted in someones elses post.

https://www.wbdg.org/FFC/NAVFAC/DMMHNAV/hdbk419a_vol1.pdf
https://www.wbdg.org/FFC/NAVFAC/DMMHNAV/hdbk419a_vol2.pdf

But the N.E.C. is really the way to go.
Something to keep in mind is that with a house of your age, I would check to see if you have current flowing on your ground system first, do a visual inspection, and take care of that paticular problem if you have it before moving on.

Thanks
Joel

 

[jim202]

Two other comments that I would like to pass along. The first is to check with you insurance company that covers the house. Ask them what their requirements are for lightning protection. The second is to look into installing a master surge protector on your electrical distribution panel. This way the whole house has some protection.

But the master surge protector on your electrical panel will need a low resistance ground for it to work effectively.

I had the only pine tree near my house take a hit that I did not cut down yet and the strike flashed over to a Magnolia tree right next to it. The Magnolia tree had a root that went over to the poured slab of my house. The slab was of a cable pre-stressed construction. The lightning strike flashed from the root into one of the pr-stressed cables and traveled around the house.

There was a master surge protector on my main power breaker panel. I had a bunch of damage done around the house to electronic equipment and telephone equipment. There was even a crack in my slab that followed a cable down the hall from the master bedroom to one of my son's room.

I had a hard time understanding why all the damage was done with the main circuit breaker panel protected and additional surge protectors at key locations. Did some serious thinking and the only thing I could come up with was the ground rod at the electrical meter did not do it's job.

The next day I brought home from work the earth ground tester we used all the time to measure earth resistance on tower sites. I killed the power to the house with the main breaker and lifted the ground wire off the house ground rod. Set up the tester with the external wires you needed to do a 3 point measurement, that run out away from the test location. The ground rod tested at about 400 Ohms resistance. I about fell over and did the test again, but moved my test ground wires to a different location. Got the same reading within a couple of Ohms.

Managed to pull out the old ground rod and drove in a new 8 foot long one I had in my garage into a slightly different location. Tested the new ground rod and got 4.5 Ohms. I was happy and had found out why all the damage was done in the house from the strike.

This is why I suggest to people that if your house is more that about 10 years old, you probably will want to replace the ground rod below your electrical meter. If your soil is corrosive, you might want to replace the ground rod even sooner.

Jim

 

[westom1]

But the N.E.C. is really the way to go.

NEC says nothing about protecting appliances. NEC's purpose is to protect human life.

Earth ground that meets NEC requirements can also be excessive impedance - compromises appliance protection. For example, an earth ground hardwire that goes up over the foundation and down to an earth ground electrode is code compliant. And compromises appliance protection. That hardwire is too long. Has sharp bends. It not separated from other non-grounding wires. Has excessive impedance. And code compliant.

Earthing to protect appliances means both meeting and exceeding what the NEC requires. That connection must be low resistance to meet code. That same wire must be low impedance to protect appliances.

For same reason, wall receptacle safety ground does nothing to protect appliances. Resistance may be 0.2 ohms and 120 ohms impedance. Trying to earth a tiny 100 amp surge means a wall receptacle can be approaching 12,000 volts. Why only approaching? An IEEE brochure demonstrates why. That plug-in protector earthed that current 8000 volts destructively through a TV in an adjacent room. Those wires were perfectly good according to NEC (to protect humans). And all but disconnected when discussing appliance protection.

Yes an earth ground electrode must have lower resistance. But that is one one part of an entire solution.

A tower often must be treated as if a separate structure. Each structure must have its own single point earth ground. Any wire in every incoming cable between tower and building must have a low impedance connection to each structure's earth ground. As demonstrated in this Tech Note: https://www.erico.com/catalog/literature/TNCR002.pdf

NEC does not require all that. Effective protection does.

 

[westom1]

Another example. A FL house suffered repeat damage to one wall. So they installed lightning rods. Lightning again struck that same wall. Problem eventually solved by fixing grounds.

Lightning rods were only eight feet long in sand. Plumbing connected to deeper and more conductive limestone. Lightning rods were fixed by installing longer electrodes into that deeper limestone. Then a bathroom wall was not damaged.

Its is more than just making a better (low resistance) earth ground. It is about how charges in a cloud three miles up connect to earthborne charges maybe four miles distant. In that case, a best connection was via bathroom plumbing until lightning rods made a better connection from cloud to those distant charges. An effective solution views the problem with that larger perspective.

 

[MUTNAV]

IMHO The guy has knob and tube wiring in half of his house. N.E.C. first. (even if it's grandfathered, I'm not certain how well that is working). Then the 419A handbooks for a complete and proper lightning and grounding system seems the way to go.

Thanks
Joel

 

[K8KPO]

This is quite an emotionally charged technical subject, as you are no doubt learning 8KPO.

Read and study all the material you can get your hands on-- and approach this scientifically.
This is advice easily given, but where to turn ?

This is my favorite place to start -

http://lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

Good Luck Cowboy !

Lauri

Yes, between this and a question I posted over on reddit I'm remembering why I gave up on all this stuff the first time around some years back. I'm getting the impression that no matter what I do my house is going to blow up so there's no point in any of this.