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Author Topic: RF in computer  (Read 2314 times)
KC4ZGP
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Posts: 1961




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« Reply #15 on: August 20, 2018, 07:13:07 AM »


Can you attach your station ground to copper water pipes? Tap water is very electrically conductive. Picture your ground system connected to miles and miles of pipes via the chemically induced tap water.

Is the computer in the near-field? Get them antennas in the backyard.

Kraus
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K5LXP
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« Reply #16 on: August 21, 2018, 06:38:40 PM »

Tap water is very electrically conductive.

So why are we using copper wires for power and antennas and not tubing full of tap water?

Quote
Picture your ground system connected to miles and miles of pipes via the chemically induced tap water.

Even if this were a perfect conductor, what would this buy you from an EMI standpoint?  Even perfect conductors exhibit reactance.  A single conductor is not a great radial field.

I'm staunchly in the camp that if there's RFI it's an antenna system problem, not a "ground" problem.  Fix the antenna, and then it's not necessary to move the problem somewhere else by shunting energy or moving a current node somewhere else on a "hot" ground.

Mark K5LXP
Albuquerque, NM
 
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AC7CW
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Posts: 1346




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« Reply #17 on: August 21, 2018, 07:21:40 PM »

Honestly, I just build monoband cf dipoles whenever possible: No tuner, less rfi, less harmonic transmission, no rf in the shack...
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Novice 1958, 20WPM Extra now... (and get off my lawn)
KC4ZGP
Member

Posts: 1961




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« Reply #18 on: August 22, 2018, 09:27:51 AM »

Mark,

I erected a LOWFER beacon. I had the wire mesh hammock above and the ground radials below.
Coil and "K" keyer sat on the ground.

I had a signal. The RF current meter's needle was moving a whole width of the needle. Blaahhh!

When I connected the radials to the copper faucet, the RF current meter swung from one end to the other.
I could even hear the meter go click, click, click as the needle slammed to the other side. I was pulling major
RF amps after that. Baby!

Other LOWFERs this side of the Mississippi could finally hear me. I could hold a fluorescent tube and it would
light up the whole back yard. My neighbor saw the flashing and thought "Sacred Bovine! What is Dr. FrankenKraus
up to now?" FrankenKraus was her invention.

So ever since that, I believe the cold water pipe ground is the best in the world. It IS a city-wide ground plane.

I don't have RFI problems by the way.

Kraus

« Last Edit: August 22, 2018, 09:34:41 AM by KC4ZGP » Logged
K5LXP
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Posts: 6136


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« Reply #19 on: August 23, 2018, 04:22:51 PM »


Your success is all well and good but you're dead wrong about tap water conductivity.  And while it's possible that a given structure's pipes make good contact with earth it's not a certainty.  My house has copper pipes coming out of the wall but many of those connect to PEX and the drain to the street is Orangeburg (concrete) pipe.  NEC no longer accepts plumbing as a service ground.  So if it works for you then wonderful, but a single pipe running out to the street even if metal is not the same as a radial field no matter how far the continuity extends.  At the frequency you describe that connection might be serving as more of an antenna than a ground.  The low frequency missile and submarine communication system I worked on in the USAF operated in the kHz range and used buried antennas.  Propagation was through, not over the earth.

Mark K5LXP
Albuquerque, NM
 
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KC4ZGP
Member

Posts: 1961




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« Reply #20 on: August 24, 2018, 06:19:36 AM »


Mark,

My ohm meter showed other wise.

My test...four ounces of tap water versus four ounces of filtered water we get at Wal-Mart.

Tap water 200,000 ohms, filtered water 400,000 ohms.

Their filter doesn't remove everything but gets rid of a lot. Even my coffee tastes like coffee
with the filtered water. Weird the tap water even has a metal-ish taste to it. My wife says peroxide.

There you go. Say hey to the family.

Kraus

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NK7Z
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Posts: 2509


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« Reply #21 on: August 24, 2018, 06:46:56 AM »

Kraus,
Mark is dead on correct, using the cold pipe system as a ground is at best lucky if it works...  A radial field will work better.  My home has PVC running to the city water, with copper pipes all through the house.  If I were to use cold water pipes as ground, my entire house would become the antenna...  As an aside, as you remove most impurities from tap water, the resistance goes up.
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Thanks,
Dave
Amateur Radio: RFI help, Reviews, Setup information, and more...
https://www.nk7z.net
K5LXP
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Posts: 6136


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« Reply #22 on: August 24, 2018, 10:33:48 AM »

Tap water is very electrically conductive.

My test...four ounces of tap water ... 200,000 ohms,


200K = "very electrically conductive" - ?

Mark K5LXP
Albuquerque, NM



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