The AM Forum
July 23, 2024, 01:14:21 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Station grounding, anything definitive  (Read 19109 times)
0 Members and 1 Guest are viewing this topic.
K6JEK
Contributing
Member
*
Offline Offline

Posts: 1188


RF in the shack


« on: May 01, 2005, 04:51:18 PM »

I thought I'd upgrade the grounding system in the shack.  A web search yieldied a torrent of conflicing opinions.  I didn't find a consensus.  Is there something reliable to read?

The current set up has each piece of equipment individually grounded to the antenna tuner  with copper braid.  Copper braid goes from there to the ground rods just outside the shack, less than 10 feet away.  Safety grounds are intact to everything with a plug.  The ground rods near the shack are not connected to the house ground.

Once upon a time, I became convinced that this was the way to do it except  the business of not tying the ground rods back to the house entry point ground.  But  that's a hell of tangle there at the antenna tuner.   I thought I'd put in a nice copper buss to get rid of the tangle.  But some think this will create problems.  Some people think these separate grounds of all variety are a bad idea in all incarnations -- tear it out all out and be happy, etc.

Incidentally, out here lightening is so rare you have a better chance of winning the lottery than being affected by it but don't tell Gerald (K6QY) that I said that.

Jon
Logged
Steve - WB3HUZ
Guest
« Reply #1 on: May 01, 2005, 06:24:53 PM »

Two good articles on the subject below. Forget all the opinions, ham radio lore and old wives tails and go with the NEC and the telco standards. You won't find much conflicting info there.

Grounding for Amateur Radio Stations by Bob, K4TAX

Lightning Protection by Bob, K4TAX
Logged
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4611



« Reply #2 on: May 01, 2005, 08:00:34 PM »

Check your homeowners insurance if you don't wanna go with the NEC standards.  We had a discussion on this on another newsgroup I'm a member  of.  One fellow thought it was a good idear to "screw the NEC" because his non-compliant ground system made for "quieter noise level".  Ain't no quieter than killing yourself and your fambly DEAD because of your stupid ham radio hobby.  Or be confronted with a burned down house and an insurance company that declines to pay.

73 John
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
KA8WTK
Contributing
Member
*
Offline Offline

Posts: 872



« Reply #3 on: May 01, 2005, 09:32:09 PM »

Looking over the web pages you noted Steve, I may be in pretty good shape here except for one thing. The tower ground rod is not connected to the "common" ground.

Here at KA8WTK, the main service entrance is at the front of the house within a couple of feet from the copper water line coming up from the street. The service entrance ground is tied to this copper pipe. The pipe then runs to the back of the house, exits the house underground, and comes up through the floor of the shack. The telco ground is connected to this copper pipe half way through the run to the back of the house.

The distribution panel in the shop is grounded to the copper pipe where it comes up through the floor. All of the equipment in the shack ties to "star" grounding points that in turn connect to a common point that is tied to the copper pipe where it comes up from the floor. It would appear that the electric service, telco and Ham gear all share the same ground.

Where I see a flaw in the system (now) is that the ground rod for the tower is not tied back to this common copper pipe ground except through coax connections. This occours because the antennas on the tower are all connected through antenna switches that are mounted on an 18" square of aluminum plate that is also grounded to the copper pipe.

Looks like I need a few feet of copper ground wire to run from the tower ground rod to the copper pipe connection. That is, if I understand what I read correctly.

I am, however, un-sure how to figure a ground mounted verticle about 100' back from the house into this. The verticle uses a pipe driven into the ground as it's mounting and ground. The information would indicate that this is the same thing as a "tower" ground.

Anyone have any ideas about the verticle and how it figures into the equation?
Logged

Bill KA8WTK
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4611



« Reply #4 on: May 02, 2005, 06:58:29 AM »

Grounding is a source of confusion even amongst those who understand the NEC well.  I recommend you buy one of those books that interprets the NEC and provides examples.

You are correct in that ALL grounds must be bonded to the service entrance grounding point.   This isn't necessarily for lightning protection as much as it is for prevention of shock/fire hazards.

73 John
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« Reply #5 on: May 02, 2005, 11:29:24 AM »

Hi Bill,

As for your vertical question....   yes, tie it's radial ground system
into the other grounds.

Over here I run an underground trench to each tower. It contains
two 4" diameter PVC pipes with 240 AC lines and three hardline
feedlines per tower. At the bottom of each trench in the dirt is
a #6 copper wire that connects to every tower's ground system.
It works it's way around the whole property tapping into the utility
pole ground, telephone ground, and anything that is grounded for
that matter.  My 160M vertical ground system consisting of 270,
300' radials also ties in... that's 15.3 miles of additional wire in
the ground.  [do not connect in the well pump system ground, except
for it's normal connections to the breaker box - at least that's what
I've been advised]

In your case, you could run a single copper wire in the ground along
with your feedline out to the tower and vertical to do the same.

BTW everything here is cad welded throughout. The tower grounds
consist of a network of 8' copper rods UNDER the concrete of each
tower all connected together with 0000 copper wire, with three
cables coming up and cad welded into the tower legs... eventually
tying into the trench cable.

Before putting in this grounding system in 1998 I used to have blown
out telephones, computers boards, etc.  Since then I have had
lightning strikes, but no damage. [I always disconnect my
antennas during thunderstorms].  I do not use polyphasers and
all that stuff, though it would be a good idea.


73,
T

Proud Member of the Bison Ass Net:
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
WA1GFZ
Member

Offline Offline

Posts: 11151



« Reply #6 on: May 02, 2005, 12:04:54 PM »

Start with NEC. Anything additional must handle the lightning current or
you will generate offset voltages. A simple matter of ohms law as our world known expert over the wall tells us.
Logged
W8ER
Guest
« Reply #7 on: May 02, 2005, 01:34:17 PM »

Tom,

I keep seeing the term "cad weld" mentioned. What is a cad weld?

--Larry W8ER
Logged
Art
Guest
« Reply #8 on: May 02, 2005, 02:33:02 PM »

Hey Larry. . . a Cadweld:
The ends of the cables to be joined are placed inside the mould. Metal welding material is then poured into the mould, a more finely ground 'starting material' is sprinkled over it and the mould cover is put in place. The process is then started by igniting the starting material with a special high-temperature flint gun, and the exothermic welding process is completed virtually instantaneously. It's just short of a controlled explosion.
Other advantages of Cadweld connections include a current carrying (fusing) capacity equal to that of the conductor and an ability to withstand repeated high current surges (faults) without any deterioration. The connections are unaffected by corrosive products to the same degree as copper.
Logged
W1RKW
Contributing
Member
*
Offline Offline

Posts: 4409



« Reply #9 on: May 02, 2005, 03:13:02 PM »

Some additional information on grounding...

http://www.polyphaser.com/ppc_ptd_home.aspx
Logged

Bob
W1RKW
Home of GORT.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« Reply #10 on: May 02, 2005, 03:17:42 PM »

Good description, Art.

More info from memory for you, Larry...

Any electrical supply house has everything you need.

The powder used to generate the controlled explosion is a magnesium compound. It attains a temperature of 5000+ degrees for an instant. What is left after the "sand-like" mold is removed is a bronze kind of metal form around the copper wires. Like a fat, well formed, brazing weld.

The mold has a life of maybe 50 shots before it begins leaking due to the wire holes getting larger from use.  

There are many types of molds... some for joining two wires together of various diameters, some for joining a wire to a flat surface, some for joining a wire to a round surface.  Diameters of everything must be specified, so it's best to standardize things if possible.

I was told by a pro NOT to Cadweld directly to a tower leg - that it changes the steel's composition. Use a flange or brace that is not part of the actual load bearing leg.... ESPECIALLY if the tower uses hollow pipe legs.

Do not look at the explosion - big time problems just like arc welding, etc.

It is a beautiful way to go. The connections can be buried and are virtually impervious to deterioration. At least mine all look like new that were done in 1998.

Each Cadweld shot comes in a small cylinder resembling a shot gun shell. A pack of twelve may cost you  $25?  and each mold was about $50? a few years back. Check current prices.

73,
Tom, K1JJ
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
W8ER
Guest
« Reply #11 on: May 02, 2005, 03:54:48 PM »

Thanks Art and Tom. I kept hearing all of this "weld this and weld that" and I pictured guys in masks and tanks going all over a tower field and that just didn't seem too reasonable.

BTW heard VU on 75 last night .. great band conditions. Brent was awesome and Skip was just about as strong here in Ohio. My antennas are down right now with two Rohn 25 towers going up and this grounding topic and process is very timely, but man .. to miss a night on 75 like last night ... ugh.

Thanks,
Larry W8ER
Logged
WA1GFZ
Member

Offline Offline

Posts: 11151



« Reply #12 on: May 02, 2005, 04:16:58 PM »

I just did some lightning test in various shielded wire types. I suggest you use the best coax you can afford. The induced voltage varies a lot with poorly configured shields. Cheap wire induces a higher voltage to the center conductor.
Logged
KB2WIG
Contributing
Member
*
Offline Offline

Posts: 4467



« Reply #13 on: May 02, 2005, 05:29:55 PM »

Is it O.K. to use oxygen free Cu for the ground?  
                                                  KLC
Logged

What? Me worry?
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4611



« Reply #14 on: May 02, 2005, 06:34:30 PM »

world's richest copper deposit discovered in marlboro[/color]

 Marlboro, CT May 2, 2215

The world's richest copper deposit was discovered yesterday under the old Cathey's Choice townhouse development north of Marlboro, said Dr. Hugh G. Rection, chairman of the Cathey Institute of Technology's Department of Mining and Metals.  "There must be thousands of tons of high-quality deposits only 10 feet below the surface," Rection said.

In an ironic twist, the old Cathey's Choice was the old homestead of the founder of the Cathey Insititute of Technology.  The institute was founded by Thomas Cathey in 2010 after he discovered schmegma, the then-revolutionary transcendental communications media that replaced radio.

Dr. Rection is also working with Harvard's Antrhopology Department to decode some old runes discovered on the property.  Each of the square-meter runestones is inscribed with the letters "K1JJ" which is thought to be a coded reference to the visitors from planet Irb in 2012.

Moe Howard, the president of the Cathey's Choice Homowner's Association, immediately file for an injunction against any further mining activity in the area.
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
W1RKW
Contributing
Member
*
Offline Offline

Posts: 4409



« Reply #15 on: May 02, 2005, 07:26:06 PM »

ROTFLMFAO!!!!!!!!
Logged

Bob
W1RKW
Home of GORT.
Fred k2dx
Moderator
Member

Offline Offline

Posts: 247



« Reply #16 on: May 02, 2005, 07:45:54 PM »

are the disposable 'one shot' types.....same thing but you crack the mold off after the welding, about $5 each.
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« Reply #17 on: May 03, 2005, 03:21:09 PM »

World's Largest  Antique  Receiver Artifacts Collection Discovered in MT AIRY MD

Mt Airy, MD -   May 3, 3015

The World's Largest  Antique  Receiver Artifacts Collection was discovered yesterday under the old  FITZSIMMONS burial grounds, said Irwin Richardt XXII.  "There must be thousands of receivers and antique tubes 10 feet below the surface," Richardt said.

It appears that old man Fitzsimmons, W3JN, 1000 years ago could not let go of his radio cache, so had them all buried in long tunnels with him, similar to the Pharohs of Egypt or like the chinese did with their 5,000 soldier statues according to Richardt.

There is evidence of bizzare rituals and radio preservation for the trip to the after life. Many of the radios that were dug up had their guts removed and muumy-like tape wrapped the remaining carcuses.

Joesph Crow XXIII  expressed interest in acquiring the stash looking to add to his vast collection empire located in Vortex, MD.

Dis-associated Press.
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
w3jn
Johnny Novice
Administrator
Member

Offline Offline

Posts: 4611



« Reply #18 on: May 03, 2005, 03:24:25 PM »

:lol:  :lol:  Touche', T!!

73 John
Logged

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
W2JBL
Member

Offline Offline

Posts: 680


« Reply #19 on: May 04, 2005, 12:48:07 AM »

where i work we have to follow a set of standards for grounding set forth by Motorola's R-56 grounding specs. the old print version was the size of a phone book, but now it can be had on CD. there's tons of really good info in there, though they take things a bit to far at times. a few years ago  a particularly anal rep from the factory was inspecting one of our sites. after he got me a bit pissed off  i asked him if he grounded his "unit" when he got in bed at night to discharge the static. this test revealed that he had no sense of humor... anyway, look up the single point grounding system in Motorola R-56 for some good tips.
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 8886


"Let's go kayaking, Tommy!" - Yaz


« Reply #20 on: May 04, 2005, 11:07:51 AM »

Hi Chris,

Can a properly installed and grounded Motorola installation absorb a direct hit to the tower/antennas and remain on the air without failure?

Big Al, K1JCL, who does commercial installations says he never disconnects his ham antennas during thunderstorms.  Obviously all commercial sites keep their antennas hooked up, but I've heard of some big meltdowns too.

I'm curious if a direct hit is very rare and part of the repair expense budget.  I would think that high towers get hit a lot.  I was told from a guy who lives on the next hill a mile from here that he watches my towers during storms and sees many strikes... though I've yet to see serious antenna damage.

Though, I took down three 6M Yagis last month and saw snakebite-like  black melt marks on all three aluminum hardlines near the antenna junctions. Like an arc jumped from the tower to the bare feedlines. Two marks separated by 2"...

BTW, I disconnect all my antennas from rigs during/before storms as a precaution..

T
Logged

Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
Steve - WB3HUZ
Guest
« Reply #21 on: May 04, 2005, 05:59:27 PM »

If your antennas are at the top of the tower they are less likely to receive a direct hit. The tower itself may get hit but it will often be below the top. Check out some of the photos and studies done by power companies. They've shown most hits on their power towers occur 2/3 - 3/4 up the tower and not at the top.
Logged
W2JBL
Member

Offline Offline

Posts: 680


« Reply #22 on: May 04, 2005, 08:08:11 PM »

don't know if Motorola claims an R56 site can stand an antenna hit, but tower hits are rarely a problem for us. antenna hits? i had a few last year, and other than melted antennas and Polyphasers, most of the time the equipment survived. in the days before we used R56 any hit- tower, phone line, power line etc. was usually fatal to the equipment. we ground our feedlines at the base of the tower (to the tower's ground rods), and again at the building entrance, then have Polyphasers mounted on a grounded copper plate just inside. all equipment also grounds to that same plate, with seperate ground wires from each cabinet. AC and phone line (tie line) surge protectors go on each cabinet as well. the room has a "halo" ring of #6 stranded bare copper ringing the ceiling that's grounded to the same common plate at the entrance. the AC service box is also grounded to the plate. outside the building a second halo is buried around the perimiter of the foundation and tied to the common plate inside. we don't yet know what's going to happen if a propane fuel tank for a generator gets hit, but it's tied into the ground system too. bet the guys from the FD would have a field day with that one!
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.068 seconds with 19 queries.