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 Post subject: RF Ground Questions
PostPosted: Sat Jan 03, 2009 12:43 pm 
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"Your ground run should go directly to the ground where you should have a ground rod for the connection point, (which will be connected to all your other ground rods in the system as discussed above). This run must be less than nine feet to be effective." - hamuniverse.com/grounding.html

"Next we need to form our RF counterpoise outside at our ground system. You will next need to add some bare copper wire at the RF feedpoint where your shack ground wire connects to. I prefer to use bare 8 gauge copper ground wire here. It is single conductor, bare copper and easily bent and run around house. Single strand is best but it should definitely be bare even if you have to strip insulation off wire. Run it around the house or anywhere it will stay out of the way fo lawn equipment but not buried deeper than 1/2 inches. This is CRITICAL. RF will not penetrate soil deeper than this at these frequencies. Those bonding wires you have between ground rods and ground rods do not exist to the RF! Burying this wire under wood chips or similar non conductive landscaping, etc is the way to go. This counterpoise should be as long as the wire antennas you have in the air. For most hams this will be about 130 feet. Longer is better. I run all the way around my house. I have found the eight gauge will push into the spacing used between driveway and foundation when persuaded with the proper tool, (READ HAMMER). You can connect the loop back on itself at the feed point." - hamuniverse.com/grounding.html


First, I'm sorry for the long quote everybody,

From the radio to the ground rod is about six feet, and Ive got enough bare 6 awg solid copper to go around my small house(about a hundred feet). Vertical antenna is mounted on the roof, grounded to its own rod, then bonded to the other ground rod for the radio. Does this loop around the house need to be buried or can it rest on the surface? The article says to connect it to the RF feedpoint, does this mean the coax connector on the radio? or the ground rod bonding point? When I loop the 6 awg back around should it be connected to the other ground rod for the antenna or back to the same rod?


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 Post subject: Re: RF Ground Questions
PostPosted: Sat Jan 03, 2009 6:17 pm 
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A ground system doesn't need to be over-engineered.

For VHF, you need absolutely no ground system at all.

For HF, depending on what kind of antenna you have, you may or may not need a good ground.

If you have a dipole, you really don't need any ground. For a vertical antenna, you need a very good ground. For modest amounts of power (100 watts or less), you don't need anything nearly as complex as what that article is discussing. I've been a ham for over 35 years, and just trying to read that made my brain hurt.

Don't sweat it. Put in a ground rod if you can, and attach it to the chasis of your equipment with the thickest wire you can find. If you have a vertical antenna, then put in as many radials as humanly possible. Beyond that, you won't really see any improvement in performance.

(Note: I am discussing grounding your station for maximum performance of your antenna. Lightning protection is an entirely different subject, although it also involves having a ground connection.)


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 Post subject: Re: RF Ground Questions
PostPosted: Sat Jan 03, 2009 7:13 pm 
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rpc wrote:
For a vertical antenna, you need a very good ground. For modest amounts of power (100 watts or less), you don't need anything nearly as complex as what that article is discussing. I've been a ham for over 35 years, and just trying to read that made my brain hurt. If you have a vertical antenna, then put in as many radials as humanly possible. Beyond that, you won't really see any improvement in performance.

Put in a ground rod if you can, and attach it to the chasis of your equipment with the thickest wire you can find.

(Note: I am discussing grounding your station for maximum performance of your antenna. Lightning protection is an entirely different subject, although it also involves having a ground connection.)


It made my head hurt too, but i thought it was because i was new. Ive been working on this stuff all day. My hf antenna will be a comet cha250b multi-band vertical, Comet claims it doesn't require radials, but i thought with a vertical hf antenna on the roof i probably should put the ground loop around the house, actually ran the wire for the ground loop around the house today. I installed the ground rods today also, went easier than i thought in January in Michigan. One for the electric service, it was previously grounded to a piece of re-bar, one for the radio chasis ground and one each for the hf antenna and vhf/uhf antenna lightning protection. Bonded all the ground rods with single ott. For the record single ott cable is a pain in the neck to work with when its 20 degrees outside.

So is 6 awg sufficient for the chasis ground?

Where do i connect the ground loop for RF? To the ground rods?


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 Post subject: Re: RF Ground Questions
PostPosted: Sun Jan 04, 2009 3:29 pm 
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Radio Chassis Ground... From the radio to the ground pole is good to reduce noise, keep it short, six feet "should" be fine, 6 gage is more than enough. If you ever receive a shock from the radio chassis then the ground wire is collecting RF just like an antenna, move to grounding strap or foil if that ever occurs.

Antenna Ground..... Your vertical antenna needs to have a ground, that is a very good connection with no solder of any type - purpose is to protect from lightning strike. The antenna probably has a specific ground point.

Vertical Antenna Radials.... In a perfect world, a vertical antenna would have counter-pose radials on or near the ground. Radials can be on top of the ground or buried a few inches below the ground. Best to do at least 10 radials, each the same wave length as the antenna. Radials help to direct the RF evenly, 360 degrees.


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 Post subject: Re: RF Ground Questions
PostPosted: Sun Jan 04, 2009 7:11 pm 
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Thanks fellas,

I've got the chassis ground covered, six feet to the rod, connected with the 6 bare and lugs, no solder. Lightning ground is going to be the same 6 bare, directly from antenna to its ground rod, connected with the ground lugs, no solder.

I'm wanting to use the 6awg copper loop all the way around the foundation as a counter poise. I should just connect both ends of the loop to the same ground rod as the chassis ground, right?


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 Post subject: Re: RF Ground Questions
PostPosted: Mon Jan 05, 2009 5:20 pm 
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I wouldn't bother with the loop around your house--it sounds like overkill. If you've already buried it, then I would say just attach it to your ground rods, and you'll have a ground system vastly superior to 99% of all hams.

The counterpoise for the vertical antenna needs to be mounted near the antenna. If the antenna is on the roof, then any additions to your ground system will have little if any effect on how well the antenna works. Generally, the counterpoise consists of radials extending out from the antenna. Ideally, the whole antenna would be mounted to a copper sheet > 1/4 wavelength on each side, which would be a more or less perfect counterpoise. Three or four radials are much better than nothing. I suspect that after about 10 or 20 radials, it would be nearly impossible to tell the difference if you add more.

I have dipoles, and I recently discovered that my station has no ground at all. I was thinking that I at least had a three-prong plug on the power supply, but it turns out that I was mistaken, and I don't even have that. I ought to add a ground for safety reasons, but with my dipoles, the complete lack of any ground makes no difference at all.

Radials added to your antenna will make infinitely more difference than digging a trench around your house. As the late Lew McCoy said, "if the damn thing works, leave it alone." It sounds like your ground is well past the "works" stage, and it sounds like it's time to have fun, rather than worrying about squeezing out the last micromho of ground conductivity.


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 Post subject: Re: RF Ground Questions
PostPosted: Mon Jan 05, 2009 7:24 pm 
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rpc wrote:
I wouldn't bother with the loop around your house--it sounds like overkill. If you've already buried it, then I would say just attach it to your ground rods, and you'll have a ground system vastly superior to 99% of all hams.



Actually, it's a bad idea to do that. You could end up with a nice charge building up on anything inside that loop.

If you have to drive extra ground rods to avoid that kind of loop, just drive the extra rods. Or bury a nice big metal plate a few feet down. But don't loop a ground around the house.

-Hans

_________________
"This does not mean, however, that we are unaware of the true meaning of the term 'security.'
To us, the term has broad meaning. It rests in the physical force embodied as it is in the ships and their base,
but also in intellectual factors among which Intelligence plays an outstanding role."
- Captain Ellis M. Zacaraias, USN


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 Post subject: Re: RF Ground Questions
PostPosted: Wed Jan 07, 2009 11:05 am 
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Sounds wrote:
Antenna Ground..... Your vertical antenna needs to have a ground, that is a very good connection with no solder of any type - purpose is to protect from lightning strike. The antenna probably has a specific ground point.


That's not entirely true. The purpose of grounding your antenna and or tower is not to "protect" them from lightning, but rather protect your house and radios from the strike. Antenna's are not, and will not be designed to withstand a direct strike, however through proper ground and lightning arrestors on your feedline, you can mitigate quite a lot of damage from making it's way into your shack.

The best bet however is to disconnect your antenna's from your radio's during an electrical storm.

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 Post subject: Re: RF Ground Questions
PostPosted: Thu Jan 08, 2009 12:24 pm 
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Standard grounding for lightning protection of commercial radio and broadcast sites include a ground ring around the perimeter of the building and lots of ground rods spaced at specific intervals around the ring. This places a reliable ground connection at every possible entry point to the building and lowers the resistance of the ground system.

The idea is to dissipate as much lightning energy into the earth and to minimize levels on cables entering the building. The AC power ground must be well bonded to the ring to keep AC power and antenna/signal ground potentials close during a strike. Even with an effective ground at the antenna, there can be thousands of volts of potential between the AC power neutral and antenna system during a strike which can destroy lots of equipment. A single point ground for AC power entry and antennas is ideal for best protection but not practical in some instances.

The ground ring is usually 500MCM bare stranded wire and ground rod connections are cad welded. Mountain top repeater sites in my area withstand direct lightning hits all the time with no damage but this level of protection is usually not possible in a residential situation. The advice of disconnecting your antenna during a lightning storm may be the only way to protect your radio equipment for most residential systems.

Effective lightning protection is probably not practical for most residential situations, commercial radio sites are designed from the ground up (pun intended) and you cannot assume you are protected just because you have an extra ground rod or two somewhere and a lightning protector on your coax. Its better to disconnect the antenna and unplug expensive equipment than to find out your lightning protection didn't work.

HHaase wrote:
rpc wrote:
I wouldn't bother with the loop around your house--it sounds like overkill. If you've already buried it, then I would say just attach it to your ground rods, and you'll have a ground system vastly superior to 99% of all hams.



Actually, it's a bad idea to do that. You could end up with a nice charge building up on anything inside that loop.

If you have to drive extra ground rods to avoid that kind of loop, just drive the extra rods. Or bury a nice big metal plate a few feet down. But don't loop a ground around the house.

-Hans


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 Post subject: Re: RF Ground Questions
PostPosted: Sat Jan 10, 2009 3:16 am 
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You know, I think I misunderstood the original post. And like others have said, that article on HamUniverse was a beast to read through. I still don't like the concept of a shallow wire loop around the house, but that probably comes from a decade of working with field wire which is a different beast altogether.

There's also something fishy article. He was talking about being zapped while transmitting, as well as tuning issues and poor transmission. That tells me there was something seriously screwy with his existing ground or antenna somewhere, and all his "counterpoise" did was fix that ground issue.

A counterpoise can be kinda complex of a concept, and probably overkill for your use.
http://www.antennex.com/shack/Dec06/cps.html

-Hans

_________________
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To us, the term has broad meaning. It rests in the physical force embodied as it is in the ships and their base,
but also in intellectual factors among which Intelligence plays an outstanding role."
- Captain Ellis M. Zacaraias, USN


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 Post subject: Re: RF Ground Questions
PostPosted: Mon Jan 12, 2009 10:24 am 
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Thanks everybody, good lightning protection info from PoorImpulseControl.

The loop around the foundation is staying, I tried listening without it and with it. It cuts a ton of noise, and seems to help pull in weak audio signals. I will bury it in the spring, can't do much digging now. The loop is connected to ground rods at all four corners of the house, each antenna has its own ground rod, and there is a ground rod for the radio chassis ground. As I mentioned before, I changed the electrical service ground from a piece of re-bar to an actual ground rod(wonder how the inspector missed that), this cut a lot of static and noise from broadcast AM and FM radio reception.

The verticals are up and running. I haven't done a lot on hf yet, but have talked with a couple of locals on 6m and 10m. 2m and 70cm seem to be where I'm spending the most time.


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 Post subject: Re: RF Ground Questions
PostPosted: Mon Jan 12, 2009 10:49 am 
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This may have been mentioned already but if not you must bond your separate antenna ground and ground ring to the house service ground. NEC states you must use #6 copper wire and there is a maximum length that I forget at the moment but it may be around 10ft. One reason for this is there can be a large difference in potential between the ground at your service panel and a ground rod at the other end of the house.

Many years ago I did this and measured 90vac between my antenna coax shield and the radios grounded with a 3 prong outlet. You would get quite a jolt removing the coax if you were touching the radio and disconnected antenna and during an FCC inspection the field engineer checking my radio almost dropped the wattmeter he was trying to connect to my radio because of a shock. The lack of warning to the field engineer was intentional.

MI-1Honkey wrote:
Thanks everybody, good lightning protection info from PoorImpulseControl.

The loop around the foundation is staying, I tried listening without it and with it. It cuts a ton of noise, and seems to help pull in weak audio signals. I will bury it in the spring, can't do much digging now. The loop is connected to ground rods at all four corners of the house, each antenna has its own ground rod, and there is a ground rod for the radio chassis ground. As I mentioned before, I changed the electrical service ground from a piece of re-bar to an actual ground rod(wonder how the inspector missed that), this cut a lot of static and noise from broadcast AM and FM radio reception.

The verticals are up and running. I haven't done a lot on hf yet, but have talked with a couple of locals on 6m and 10m. 2m and 70cm seem to be where I'm spending the most time.


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 Post subject: Re: RF Ground Questions
PostPosted: Mon Jan 12, 2009 11:29 am 
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The ground rods are all bonded, together and to the service ground rod, with single ott stranded, with the proper lugs. The 6 awg bare ground loop is bonded to all rods also, with the same lugs made for connecting stuff to ground rods.


Thanks for the heads up tho! Anything that keeps me from burning down the house or getting zapped is always greatly appreciated!!!!!


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