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Author Topic: Proper grounding for HF setup  (Read 1163 times)
KC8QHR
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Posts: 2




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« on: August 12, 2002, 07:44:05 AM »

I've been off the air for several years due to living in apartments where antenna space has been slim to non-existent. Now, I have my own house (yay!), with a nice large backyard for my antenna. However, proper grounding is something I've always had trouble with and I want to reduce TVI/RFI as much as humanly possible. My deed has covenants, but right now, there's no enforcement, and every house in the development has at least one violation on their properties. I intend to use this to my benefit, but at the same time I don't want to provide ammo. SO, on to the heart of the question.

I already plan on purchasing a low-pass filter for my shack to help in the effort. My house is manfactured, and I've put it on a permanent foundation with a crawlspace. So I have two possible routes for my ground cabling, through the floor and into the earth underneath, or through the side and out a few feet to avoid the french drain. What would be the best way to provide the ground? A copper rod, a bunch of rods, etc? What is the best wire to connect to the ground? The manual for my TS-830S (as battered as it is), suggests as short and heavy a lead as possible. I've given thought to 14 gauge standard house wire.

I have one other option, but I'm not sure if it would work. My house has grounded outlets throughout. Would it be possible to route the ground through the ground plug of one of these outlets? Being a new home I don't have the luxury of copper piping for my water unfortunately.

Any thoughts, suggestions, 'I wouldn't do that if I were you's? Smiley Anything would be appreciated.
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N4ZZK
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« Reply #1 on: August 12, 2002, 08:18:18 AM »

From an RF standpoint, you want to use wide braid (1/2 inch or wider is good) rather than standard 14 gauge copper wire.  This provides a good low impedance path for the RF.  Each piece of equipment should have a braid to a common point which should go to the station ground.

Several ground rods, bonded together and also bonded to the electrical entrance ground if possible are part of a good ground system.  

There is a series of vy good articles recently published in QST addressing grounds from an RF, lightning,  and AC safety standpoint.  Well worth the time to read over them.

GL and 73,
Al N4zzk
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N4ZZK
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« Reply #2 on: August 12, 2002, 08:19:21 AM »

From an RF standpoint, you want to use wide braid (1/2 inch or wider is good) rather than standard 14 gauge copper wire.  This provides a good low impedance path for the RF.  Each piece of equipment should have a braid to a common point which should go to the station ground.

Several ground rods, bonded together and also bonded to the electrical entrance ground if possible are part of a good ground system.  

There is a series of vy good articles recently published in QST addressing grounds from an RF, lightning,  and AC safety standpoint.  Well worth the time to read over them.

GL and 73,
Al N4zzk
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WB2WIK
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« Reply #3 on: August 12, 2002, 09:39:38 AM »

Grounding normally has little to nothing to do with RFI/TVI or its prevention.  The TS830S should not need an outboard low-pass filter; I'd be absolutely shocked if the filter made any difference at all, other than to lighten your wallet a bit.

Best ways to avoid RFI/TVI:

-Keep your antennas as far away as possible from your neighbors' homes and the electronic equipment contained therein.  There's no substitute for "distance" when it comes to interference prevention.

-Do not use the electrical system ground (third wire) for anything other than what it's there for, which is a return to prevent shock hazard in the event of wiring or equipment malfunction.  Don't connect anything to this ground, except the green wire in your power cords.

-Try to convince all neighbors to subscribe to either cable TV service, or Direct TV (DSS) service, so that nobody is trying to receive TV signals "off the air" using television antennas.  

I run 1500W output power on eight bands in my very tightly-packed neighborhood (1/4-acre suburban lots, with homes very close together), and have absolutely no RFI/TVI of any kind in my own home or any of the neighbors'. And I have no ground system of any kind, at all.  Nothing I have is intentionally grounded.  Makes no difference.  But all neighbors are using cable TV or satellite TV, and nobody is even attempting to use their own TV antenna to receive signals...this makes all the difference!

WB2WIK/6
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KC8QHR
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« Reply #4 on: August 12, 2002, 11:07:43 AM »

My development is rather similar, 1/3 acre lots. Everyone in the development has DSS or cable, only one guy has an antenna up and he's only using it to pull in our local networks since DSS won't carry them around here. Hopefully that will keep the interference down.

My antenna is an MFJ G5RV, and I'm putting it up at about 30 feet between a tree right outside my house and a pole I hope to erect soon at the far end of my lot, which is around 120', and the antenna's only 102'. Distance wise, since the tree is right dab smack in the middle of my lot, this should put about 40 feet between the antenna and my next door neighbors.

I may be running off of false assumptions, as I had a lot of interference between my rig and our TV's at my parents house a while back, but that was before I knew that having a ground wire of great length (it was probably 30 feet) can act as a second antenna. I shortened it later with some aluminum braid I got out of some shielded cable and I believe that did the trick, if I recall correctly, but it was still a long wire. This time, following the suggestions above I plan on having three ground rods tied together with copper braid running into my house, a total run of about 7 feet, since I have to get out past the french drain.
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RobertKoernerExAE7G
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« Reply #5 on: August 12, 2002, 01:14:13 PM »

Check out this site for a good discussion of all the different grounds we encounter in ham radio.

http://www.cebik.com/radio.html


Own home YEA!

Have FUN
Bob
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K1BRF
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Posts: 36




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« Reply #6 on: August 12, 2002, 05:04:11 PM »

For ELECTRICAL & LIGHTNING-STIKE grounding, I think the July and August articles in QST are far and away the best and most practical things I have ever read on the topic.

For RF grounding (which as a number of folks have pointed out is largely unrelated to electrical grounding), the MFJ artificial ground or some counterpoise wires and the usual items: Filtering [see August QST product survey], short, well dressed leads, use of braid, good equipment, tight connections and a hundred other large and small things which are all detailed in the ARRL antenna and RFI books.  That RFI book is worth reading even if you do not have a problem because it will tell you every possible cause and how to address it.

Good luck.
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K9KJM
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Posts: 2415




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« Reply #7 on: August 12, 2002, 09:44:05 PM »

Wide flat copper "strap" is the best material to use from inside the shack to the outside ground "system"
1 1/2" would be the minimum width I would consider, 3" wide is better, and nowadays, Commercial stations use 6" wide copper strap. This strap can be purchased from AES and others, But if you can find an "upscale" roofing company, you might get the same material for a lot less!
Best way to make electricial connections for the average person is with true "silver solder" as used in the refrigeration trade, purchased at welding shops. Use "Mapp" gas in a standard "propane" type torch to heat the copper joints. (The pros now use "Exothermic" or "Cadweld" to make the connections, But unless you know someone who will lend you the ceramic "forms" this is too expensive for the average ham to consider.  
As others have said, The series of recent articles in QST magazine are GREAT!    Or, check the tech. notes
at the Polyphaser website.  The QST articles are aimed at lightning protection, But if followed, will also make a pretty good "RF" Ground system. (Ground rods are good for DC safety and lightning protection only, And do nothing for an "RF" ground system.)
Do not use copper "braid" especially outdoors. As it
ages it will cause strange problems at RF.
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AB8PR
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Posts: 26




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« Reply #8 on: August 13, 2002, 04:01:11 AM »

KC8QHR here, my new callsign just popped into the FCC database. Smiley

Thanks for the suggestion on the copper strapping. I'm planning on burying it out to the ground rod so weathering is definitely a concern. Otherwise it's bound to be a tripping hazard or get sliced by my mower as it'll be in a high traffic area.

I got the idea about the RFI from the manual for my rig, it recommended grounding for both shock prevention and to reduce the possibility of TVI/BCI as it put it. Being a stubborn teenager at the time I didn't read the cautionary note right below it about having a ground wire 1/4 wavelength or longer. Wink

Here's another question about routing the coax. I'm leaning towards bringing it straight in through the side of the house. That's how the DSS guys brought in the cable from my dish. Only thing I don't like about that is that I have to drill two holes, since I'll have my HF antenna and my VHF antenna. I've given thought to some sort of box on the side of the house with a conduit going through the wall so I could run multiple cables through it. How would you recommend constructing something like that? Maintaining the insulation is my primary concern.
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WB2WIK
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Posts: 20595




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« Reply #9 on: August 13, 2002, 06:59:07 AM »

Congrats on the new call!

Don't worry about drilling holes in your house, nobody will ever know about them except you.  However, if you want a "flexible" method of bringing in cables, one which can be used for many years to come as you add more antennas, you might consider a dryer exhaust vent and the rather large (4") hole it requires, which needs to be installed just once.

Advantages:

Dryer vents only cost a few dollars, and they look like they're supposed to be there, since most homes have one, anyway.

They are very weatherproof/waterproof, and even more so if you apply RTV sealant during installation.

If it oxidizes, rusts or starts looking crappy, it's easy to replace with another one for $5, and that operation only takes a minute.

It leaves enough room for about 10 full-size cable runs, including coaxial, rotor cable, whatever, and you can take up any space left by jamming weatherproofing foam material in alongside the cables.  That will keep out heat, cold and wind, and also keep out tiny critters that may try to enter via the vent.

It's a 4" hole, but only needs to be made once, and should last you forever.

WB2WIK/6
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