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Author Topic: Station ground question  (Read 1173 times)
AB0IO
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Posts: 12




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« on: July 19, 2004, 07:44:05 PM »

WB2WIK, I don't want to get into an argument, but your reply makes many assumptions that are not necessarily correct.  I do not dispute that the ground lug is for an RF ground.  Duh.  That does not mean it cannot be used for a safety ground should one desire to do so.

As for antenna tuners not requiring power, well, in general that is not true.  Auto tuners are an obvious counter example.  My model 238 tuner draws B+ from my Omni VI.  I'm sure there are other examples as well.

As for rigs from the 60s and 70s, most of the ones I recall (the ones with the big, hot, glowing glass thingies) had a ground lug on the rear of the chassis.  You sure you were around back then?

All I was after was info on the electrical properties of concrete.  Guess I screwed up the query pretty bad.
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AB0IO
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« Reply #1 on: July 16, 2004, 08:49:23 PM »

I will be installing an earth ground for my station, and was wondering if connecting the ground wire to a bare concrete basement floor would suffice.  Anybody have any thoughts on this?  I can always go out the window to a rod driven into the earth, but it seems like a floor connection would accomplish about the same thing.
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AA4PB
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« Reply #2 on: July 17, 2004, 12:31:32 PM »

No, attaching the ground wire to a concrete floor will not be sufficient. Concrete is not all that conductive.

The next question arrises - what are you trying to accomplish with the ground? If its lightning protection you should ground the shields of the coax to a ground rod right where they enter the building. If its an RF ground, it won't work well with 15-20 feet of wire connected between the radio and the ground rod (inductance in the wire). If your antennas are balanced (such as a dipole) then you shouldn't need an RF ground at all.
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AB0IO
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« Reply #3 on: July 17, 2004, 12:57:39 PM »

Thanks for the response.  I guess I could have clarified my intent by asking "how conductive is concrete?"  since I looking at an electrical/safety ground, not an RF ground.  Right now all paths from the station to cold water pipes, outdoor to a ground rod, etc. are 20 feet or more.  I was hoping to both shorten this path and hide it visually.
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K5CEY
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« Reply #4 on: July 17, 2004, 03:55:28 PM »

For an electrical/safety ground it is not uncommon to drill a hole thru the concrete floor and then drive an 8 foot ground rod into the earth below.
                        John
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AA4PB
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« Reply #5 on: July 17, 2004, 07:25:21 PM »

Question - doesn't your home's electrical system already have an electrical/safety ground? The ground pin on the outlet should serve this purpose without adding another. With an electrical/safety ground the length of the run (within reason) shouldn't matter. It's purpose is to provide a path back to the electrical service panel to blow the circuit breaker in the event that a metal case component gets shorted to the hot leg.

Now a lightning gound is a different animal. In that case you want to ground the various coaxes, rotor wires, etc. just before they enter the house.
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AB0IO
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« Reply #6 on: July 18, 2004, 01:12:03 AM »

"Question - doesn't your home's electrical system already have an electrical/safety ground?"  

True enough.  But I'm a suspenders-and-belt kind of guy.  If they put a ground wire connection on the back of the tranceiver and antenna tuner, I'm inclined to use them.  ;-)
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N8UZE
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« Reply #7 on: July 18, 2004, 09:14:07 AM »

You can run your ground wire from the connectors on the back of your radio and tuner to the ground connection in the outlet if you have grounded outlets.
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WB2WIK
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« Reply #8 on: July 19, 2004, 11:54:42 AM »

The "ground terminal on the back of the radio" comment is a pretty common one but shows a misunderstanding of the intent.

That terminal needn't actually be there, and didn't exist in hundreds of ham equipment models for decades.  It's not a U.L. or electrical code requirement of any sort, either.  It's there primarily for the handy addition of a station *RF ground* should one be required (which it usually is not), and the manufacturers started including this when rigs started coming in from Japan.  The older American transceivers of the sixties and seventies mostly did *not* have such a terminal, and nobody missed it.

Surely an antenna tuner requires no "safety" ground, since it shouldn't contain any active powered circuitry that could be a potential hazard.  The terminal is for *RF* ground, only.

The only important *safety/electrical service* ground is the one that connects to the green wire in your electrical outlet and is common to the "earth" bus in your electrical service panel, whether that point is actually grounded or not.  (It should be, but even if it were floating, this would still be the correct "safety" ground connection point.)

Concrete is not an electrical conductor.  It's not the greatest insulator, either, but on a conductivity scale it ranks very poorly compared with metals used as electrical conductors.

WB2WIK/6
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WB2WIK
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« Reply #9 on: July 20, 2004, 11:45:31 AM »

AB0IO, the "B+" your model 238 uses is 12vdc to power a meter lamp.  It's also completely isolated from earth and the AC power line, so there is no safety ground required for that.

A "safety" ground only applies to equipment containing mains-powered systems like an AC-to-DC power supply.  If the equipment is not directly powered by the AC mains, all the safety grounds in the world won't help, or do anything.

The requirement for a "safety" ground was prompted by electronic equipment lacking an isolation transformer, such as many older tube-type radios, and even bedside clock radios, from the 1950s and 1960s.  Those used only a 2-wire power cord, had no safety ground of any sort, and many had no isolation transformer, either!  They rectified the AC mains directly and had series-connected tube filaments the sum of which totalled 120v, so they didn't need a filament transformer.  These were accidents waiting to happen, and ironically, most of them had no "chassis ground" connection point of any sort.  They were responsible for many electrical shocks, and even a few fires.  Such design and construction is no longer lawful here, nor used by anybody.

Yes, I was around "back then" (in the 1960s etc), and have been licensed for 39+ years now.  Many of my older vintage ham gear had no ground stud or terminal, although some did.  It was common for the older gear, as it aged, to develop internal ground faults that caused the user a mild shock if the chassis was *not* grounded, and sometimes you'd see a small spark as a ground was connected if the equipment was plugged in!  That was usually due to leaky bypass capacitors bridging the AC line, and the proper solution isn't to ground the equipment, but to replace faulty components.

I ran a Class A dealership and service center for Hammarlund, Hallicrafters, E.F. Johnson, R.L. Drake, Collins Radio, Swan Electronics and Squires-Sanders/Clegg for a few years back "in those days" (late 1960s) and serviced everything these companies made, doing both in-warranty and after-warranty repairs.

73,

Steve WB2WIK/6
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KF4WXD
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« Reply #10 on: August 02, 2004, 02:48:41 PM »

You may be referring to a "Ufer ground".  This is a method whereby the rebar in the foundation is bonded together and a lead is brought out through the concrete.  The considerable suface area of the concrete bonds to the earth providing an excellent ground.

Russ - kf4wxd
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K1CJS
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« Reply #11 on: August 03, 2004, 08:09:11 PM »

Running a wire from that ground lug to the center screw of your outlet isn't a good idea.  It may cause more problems than it would cure--many more.  If you insist on using a ground wire from that lug, run it to a ground point, either a water pipe or a ground rod.  In either case, if the distance to actual ground is longer than a few feet, you may be causing yourself problems you would be wise to avoid.
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