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Author Topic: Grounding  (Read 479 times)
W4CLQ
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Posts: 18




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« on: July 22, 2004, 01:17:51 AM »

anybody ever ground there rig into the groung hole on a wall socket.  Is this a good idea?

SS
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9V1VV
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Posts: 31




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« Reply #1 on: July 22, 2004, 05:05:52 AM »

Hi,
Remember that the ground connection in the house/apartment may have a long and winding road to travel before it reaches true gound. This means that it can act as part of your transmitting system and radiate RF into other appliances, or cause your rig to radiate. I am lucky and live in a low apartment with an excellent copper waterpiping system and use this. A field strength meter shows that my shack equipment is at a good ac (rf) ground, and a ground conductance meter shows me that it is less that 0.25 ohm off true DC ground. It all depends on your circumstances and where you are operating from. Sometimes there is no choice if you are in a high apartment with poor or plastic piping - then you must use the electrical system earth. If you are in a ground floor use a good galvanised iron spike into wet earth  with a thick copper cable to your equipment. Use a common earth star point in the shack : don't daisy-chain your stuff together. If you have loads of space on the ground, dig a trench, lay a copper plate inside, cover with coal dust and earth and connect that to your shack  using copper cable. Bury a pipe and pour water down every week or so in the dry season.....the best earth you can get will increase your radiation effiency (no wasted energy thrown into the house earth !) and reduce RFI....hope this helps.
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W4TYU
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Posts: 518




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« Reply #2 on: July 22, 2004, 06:29:52 AM »

The third wire in the convenience outlet is used for electrical safety grounding of items. It is not for RF grounding of radio transmitters.  Also electricians have been known to make mistakes and have this "round" hole electrically hot.

In truth, you may not need an RF ground for your equipment. This depends mostly on the type of antenna you use.  It is good practice to connect all of the equipment to a common point to avoid "ground loops"

Ole man JEAN

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AA4PB
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Posts: 12638




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« Reply #3 on: July 22, 2004, 06:49:54 AM »

Lets hope that electricians are not wiring the round hole to a hot wire!  This is an electrical safety ground that runs back to the service entrance panel. It's purpose is to cause the breaker to blow in the event of the failure of a piece of equipment that causes the outer case to be shorted to the hot wire. Without this safety connection, the case would have 120V applied and become a personnel hazzard.

Any equipment with an exposed metal chassis that is connected to the power system (generally the power supply) should have the case connected to the safety ground. This is generally done thru the third wire in the power cord.

This ground is NOT a good RF ground because the lenght of the wire run is too long before it reaches any earth ground. There is normally no need to make a separate connection between the rig and this ground.
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W4CLQ
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Posts: 18




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« Reply #4 on: July 22, 2004, 07:26:03 AM »

I live in an apartment (3rd floor) and I am just looking for the best ground.  How about the radiator?  9v1w mentioned a water system.  
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K5DVW
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Posts: 2193




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« Reply #5 on: July 22, 2004, 09:11:20 AM »

Why do you need a ground, anyway?
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KT8K
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Posts: 1490




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« Reply #6 on: July 22, 2004, 09:46:32 AM »

There are lots of good grounding articles here on eHam - do a search.  I learned a lot that way.  There are also references to other websites and reference materials on grounding in those articles.

Keep in mind, there are three kinds of grounds:  
1. Safety ground (the third pin) - to protect you in case of an equipment failure or power short,
2. RF ground - usually a counterpoise or ground plane, typically not needed by resonant, balanced antennas such as dipoles and yagis, and
3. Lightning Protection ground - usually in the form of ground rod(s) and associated wiring, ground busses, and lightning arrestors.
Each of the three is based on separate needs and concepts, though they may share some hardware (for example, it is specified in electrical codes that the ground rod(s) used in the lightning ground system be connected to the safety system ground rod).
Happy reading.  73 de kt8k - Tim
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WB2WIK
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Posts: 20537




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« Reply #7 on: July 22, 2004, 12:54:33 PM »

If K5DVW hadn't already asked it, I would have asked the same thing: "What makes you think you need a ground?"

Only with a good answer to this question can intelligent suggestions be provided...

WB2WIK/6
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WA1RNE
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Posts: 823




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« Reply #8 on: July 22, 2004, 01:47:02 PM »


 As others have stated, you can do this but if you are trying to solve an antenna performance problem or if the shack is "hot" with RF it will not be an effective RF ground and will not likely solve your problem.

 Many transceivers have an earth ground built in to the line cord so it would already be done for you and would serve only the intended purpose - acting as a safety ground.

 Personally, I have been an advocate of a good RF station ground mainly for 2 reasons:

 1) Lightning protection; I think it's a good practice to short out the ends of all feedlines at the shack and short them to a good RF ground during  lightning storms. To do this requires using either a ground rod (or more than one depending upon your soil conditions) or the main copper water feed to the house using as short and low inductance connection as possible. I've used a length of copper braid from RG-8/U coax and even coppper flashing cut to ~3" wide. Use the Radio Amateurs Handbook or Antenna book for  guidance.

 2) Keeping the chassis of each rig, amplifier, antenna tuner, etc. bonded at relatively the same point is good practice. But if you should experience a problem with an antenna due to a failed connection or from just plain experimentation especially if you like to run high power, any spill over currents on coaxial lines or imbalance on tuned feeders could end up making your shack hot. Most guys will say #2 is unlikely but it has happened to me over my 31 years in the hobby. You know, the live and learn thing???
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AA4PB
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Posts: 12638




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« Reply #9 on: July 22, 2004, 05:10:48 PM »

If it's a hot water radiator connected with metal pipe then it may provide a decent counterpoise for an end fed wire or other unbalanced antenna. If you are using a dipole or some type of balanced antenna then the RF ground should be unnecessary.
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K1CJS
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Posts: 5809




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« Reply #10 on: July 22, 2004, 07:19:44 PM »

In a word--NO!

You may be doing more harm than good by trying to ground your system unless you have a direct path to ground.  Who knows what is connected to that water pipe/heating system pipe you're contemplating using, especially in an apartment building.

If somebody else has a piece of equipment using that potential ground that goes bad, it may drop 110 volts or more right onto your equipment!
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AA4PB
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Posts: 12638




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« Reply #11 on: July 22, 2004, 08:02:08 PM »

If somebody else has a piece of equipment using that potential ground that goes bad, it may drop 110 volts or more right onto your equipment!
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Well, if that happens then the building wiring is not in accordance with the National Electric Code and it represents a personnel hazard. #1-the heater pipes should be connected to the safety ground on the electrical service panel to prevent just such a thing. #2-the bad equipment should have been connected to the electrical safety ground via the third pin on the plug rather than being connected to the hot water pipes to serve as the safety ground.

It is true that using the pipes for an RF ground (counterpoise) "could" spread RF around the building and cause RFI. You just have to try it and see. On the other hand, if the pipes run all over the building and cover a rather large area they can serve as an acceptible counterpoise. I've done it successfuly several times. End fed wire coming in the window. Tuner located at the window and connected to the radiator located directly below the window. Running 100W SSB. From the midwest, worked plenty of DX on 20M and kept a regular weekly sched with Central America. Checked into state nets on 75M. Never any RFI reported.
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K1CJS
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Posts: 5809




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« Reply #12 on: July 23, 2004, 11:19:08 PM »

If somebody else has a piece of equipment using that potential ground that goes bad, it may drop 110 volts or more right onto your equipment!
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Well, if that happens then the building wiring is not in accordance with the National Electric Code and it represents a personnel hazard.
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You should know as well as I do that repairs and installation of other household equipment may have altered original wiring and grounding systems.  And please don't say it cannot happen, especially in older buildings.  It shouldn't happen is a lot different than it can't happen.
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