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Grounding negative side of power supply?

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Jim Brown-10

Re: Grounding negative side of power supply?

On Mon, 19 Apr 2010 19:36:29 -0500, Bob McGraw - K4TAX wrote:

>Now, with the radio connected between the receiving
>antenna and the AC mains, the path for the current difference is through the
>radio and power supply.

I'm with Tom on this one. Here's why. First, remember that lightning is NOT
DC, it is RF, with spectra VERY broadly centered around 1 MH. Second, the
coax from the antenna MUST be bonded to the building entry panel, and from
there to all the house grounds. Third, the coax from the RX antenna SHOULD
have at least one big honker ferrite choke on it at the antenna end, and
another near the station. In other words, there should be at least several K
ohms in series with the coax at the frequency of lightning. That causes
lightning to seek a lower impedance path to earth than one through the house
(and the shack). Like the ground rod at the antenna.

Bottom line -- I don't see a bond helping lightning safety, and as Tom has
noted, it sure doesn't help with RX noise.

73,

Jim K9YC

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Bob McGraw - K4TAX

Re: Grounding negative side of power supply?

Refer to the NEC. It's their rule.

As a side note, a loss of property covered by insurance may be dissallowed
if they find improper grounding contributed to the damage. And they
reference the NEC with regard to "proper".

73
Bob, K4TAX

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Elecraft List" <[hidden email]>
Sent: Monday, April 19, 2010 7:49 PM
Subject: Re: [Elecraft] Grounding negative side of power supply?

> On Mon, 19 Apr 2010 19:36:29 -0500, Bob McGraw - K4TAX wrote:
>
>>Now, with the radio connected between the receiving
>>antenna and the AC mains, the path for the current difference is through
>>the
>>radio and power supply.
>
> I'm with Tom on this one. Here's why. First, remember that lightning is
> NOT
> DC, it is RF, with spectra VERY broadly centered around 1 MH. Second, the
> coax from the antenna MUST be bonded to the building entry panel, and from
> there to all the house grounds. Third, the coax from the RX antenna SHOULD
> have at least one big honker ferrite choke on it at the antenna end, and
> another near the station. In other words, there should be at least several
> K
> ohms in series with the coax at the frequency of lightning. That causes
> lightning to seek a lower impedance path to earth than one through the
> house
> (and the shack). Like the ground rod at the antenna.
>
> Bottom line -- I don't see a bond helping lightning safety, and as Tom has
> noted, it sure doesn't help with RX noise.
>
> 73,
>
> Jim K9YC
>
>
> ______________________________________________________________
> Elecraft mailing list
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W8JI

Re: Grounding negative side of power supply?

<Refer to the NEC. It's their rule.

As a side note, a loss of property covered by insurance may
be dissallowed
if they find improper grounding contributed to the damage.
And they
reference the NEC with regard to "proper".>

I'm not so sure we aren't getting carried away with our own
interpretation of NEC rules here. We also have to apply a
little technical "common sense" to our systems.

I have antennas and towers scatter over thousands of feet
distance. It would be totally worthless and physically
impossible to bond the ground rods on my antennas to my
mains ground. The additional protection to my house and
equipment, and to people, would be zero.

In addition to no improvement in protection, the
effectiveness of the low-noise antennas would be greatly
decreased.

Then we have to consider odds that power lines, trees, and
our large towers would be ignored by lightning and a small
ten-foot-tall twenty-foot-long, antenna would be struck. If
it were struck, where would the majority charges move? In
the feeder to the house. If the feeder ground were bonded to
the mains ground at the building entrance, the safety issue
for people and the dwelling is closed at that point. The
ground at the dwelling entrance, that is mandated by NEC to
be bonded to the mains ground, is key to safety. Not the
critical signal ground at some backyard clothesline antenna.

I also frequently hear that "insurance disallowed"
statement. If insurance was "disallowed" for a NEC safety or
rule violation, very few claims would ever be paid. In my
entire life I can't recall having a claim denied because of
something like this. I would bet well over half of Ham
stations lack a proper entrance or station ground bonded to
the mains ground, but I don't recall ever knowing of a claim
disallowed for that gross error.

73 Tom

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Jim Brown-10

Re: Grounding negative side of power supply?

On Tue, 20 Apr 2010 06:31:04 -0400, Tom W8JI wrote:

>I'm not so sure we aren't getting carried away with our own
>interpretation of NEC rules here. We also have to apply a
>little technical "common sense" to our systems.

>I have antennas and towers scatter over thousands of feet
>distance. It would be totally worthless and physically
>impossible to bond the ground rods on my antennas to my
>mains ground. The additional protection to my house and
>equipment, and to people, would be zero.

Exactly. My interpretation is that NEC requires the bonding of
the shack, and coax entry points with power system ground and all
other grounds directly associated with the house, AND with a
tower physically attached to or very close to the house, but NOT
with a remotely located antenna or tower.

My 120 ft tower is about 250 ft from the shack and 120 ft from
the house, and is well grounded at its base. It's surrounded by
several dozen redwoods, about half of which are at least 40 ft
taller. I've never considered bonding it to either structure, and
I wouldn't treat it differently even if the trees weren't there.

73,

Jim K9YC

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Edward R Cole

Re: Grounding negative side of power supply?

In reply to this post by Joe Planisky

------------------------------

Message: 26
Date: Tue, 20 Apr 2010 06:31:04 -0400
From: "Tom W8JI" <[hidden email]>
Subject: Re: [Elecraft] Grounding negative side of power supply?
To: "Bob McGraw - K4TAX" <[hidden email]>, "Jim Brown"
<[hidden email]>, "Elecraft List"
<[hidden email]>
Message-ID: <321074F178104F4FAB7715A73E6D11CF@radioroom>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

<Refer to the NEC. It's their rule.

As a side note, a loss of property covered by insurance may
be dissallowed
if they find improper grounding contributed to the damage.
And they
reference the NEC with regard to "proper".>

I'm not so sure we aren't getting carried away with our own
interpretation of NEC rules here. We also have to apply a
little technical "common sense" to our systems.

I have antennas and towers scatter over thousands of feet
distance. It would be totally worthless and physically
impossible to bond the ground rods on my antennas to my
mains ground. The additional protection to my house and
equipment, and to people, would be zero.

In addition to no improvement in protection, the
effectiveness of the low-noise antennas would be greatly
decreased.

Then we have to consider odds that power lines, trees, and
our large towers would be ignored by lightning and a small
ten-foot-tall twenty-foot-long, antenna would be struck. If
it were struck, where would the majority charges move? In
the feeder to the house. If the feeder ground were bonded to
the mains ground at the building entrance, the safety issue
for people and the dwelling is closed at that point. The
ground at the dwelling entrance, that is mandated by NEC to
be bonded to the mains ground, is key to safety. Not the
critical signal ground at some backyard clothesline antenna.

I also frequently hear that "insurance disallowed"
statement. If insurance was "disallowed" for a NEC safety or
rule violation, very few claims would ever be paid. In my
entire life I can't recall having a claim denied because of
something like this. I would bet well over half of Ham
stations lack a proper entrance or station ground bonded to
the mains ground, but I don't recall ever knowing of a claim
disallowed for that gross error.

73 Tom
===========================
Tom, and all:

Have to agree with you.
Hundreds of feet of electrical ground wire from antennas? Not even
sure that would work for lightening.
I have a ground rod at the base of my 600m inverted-L antenna (RF
ground) and the 2-ft wide x 50-foot to 70-foot long radials are
connected there.
Z = 18 - j681.5
Rad = 0.8 ohms so most is ground loss

I have a 120-foot run of 1-5/8 inch LDF7-50A Heliax that is grounded
at the base of the tower and at the cable entrance to the shack. The
cable entrance is a 12x 16 inch aluminum plate that has 26 coaxial
feed thru connectors (I have over 17 antennas). The mains
(electrical meter box) is grounded on the other side of the house so
to bond them would take 50+28+50= 128 feet of ground wire. That
might be effective if It was #6 or larger. I got better places to spend money.

My Beverage antenna has two ground rods at either end but is 150-feet
from the cable entrance. I have begun using ferrite RF Chokes a lot
on my coax with excellent results. They are not expensive and nicer
to look at then a big coil of coax.

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010
DUBUS Magazine USA Rep [hidden email]
======================================

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W8JI

Re: Grounding negative side of power supply?

<<<I have a 120-foot run of 1-5/8 inch LDF7-50A Heliax that
is grounded
at the base of the tower and at the cable entrance to the
shack. The
cable entrance is a 12x 16 inch aluminum plate that has 26
coaxial
feed thru connectors (I have over 17 antennas). The mains
(electrical meter box) is grounded on the other side of the
house so
to bond them would take 50+28+50= 128 feet of ground wire.
That
might be effective if It was #6 or larger. I got better
places to spend money.>>>

I disagree only on this one point Ed. The entrance ground
must be bonded to the mains ground. Not doing so sets us up
for very big problems.

As a matter of fact the better we ground our entrance panels
and our antennas, the more we set ourselves up for problems
from hits on the power line or power line faults.

My ground bonding connection runs directly under the house
with wide flashing to my mains ground. I also have a halo
ground surrounding the house that bonds my TV tower and
everything else entering the house to my mains ground and
entrance ground.

73 Tom

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Jim Brown-10

Re: Grounding negative side of power supply?

On Tue, 20 Apr 2010 16:19:47 -0400, Tom W8JI wrote:

>I disagree only on this one point Ed. The entrance ground
>must be bonded to the mains ground. Not doing so sets us up
>for very big problems.

RIGHT ON.

Jim K9YC

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Bob McGraw - K4TAX

Re: Grounding negative side of power supply?

In reply to this post by Jim Brown-10

At my shop sits my 100 ft tower for the 3 repeaters and one of my HF
stations. Some 50 ft away is a old Hickory tree that's about 60 to 70 ft
tall. Two years ago I received a lightning strike that destroyed the
tree. No damage to the tower, any of the 12 antennas on the tower or any
of the equipment in the two racks in the building. The tower and
equipment was correctly and properly grounded. The tree wasn't.

73
Bob, K4TAX

> On Tue, 20 Apr 2010 06:31:04 -0400, Tom W8JI wrote:
>
>>I'm not so sure we aren't getting carried away with our own
>>interpretation of NEC rules here. We also have to apply a
>>little technical "common sense" to our systems.
>
>>I have antennas and towers scatter over thousands of feet
>>distance. It would be totally worthless and physically
>>impossible to bond the ground rods on my antennas to my
>>mains ground. The additional protection to my house and
>>equipment, and to people, would be zero.
>
> Exactly. My interpretation is that NEC requires the bonding of
> the shack, and coax entry points with power system ground and all
> other grounds directly associated with the house, AND with a
> tower physically attached to or very close to the house, but NOT
> with a remotely located antenna or tower.
>
> My 120 ft tower is about 250 ft from the shack and 120 ft from
> the house, and is well grounded at its base. It's surrounded by
> several dozen redwoods, about half of which are at least 40 ft
> taller. I've never considered bonding it to either structure, and
> I wouldn't treat it differently even if the trees weren't there.
>
> 73,
>
> Jim K9YC
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

Bill Coleman-2

Re: Grounding negative side of power supply?

On Apr 20, 2010, at 7:52 PM, Robert Mcgraw wrote:

> At my shop sits my 100 ft tower for the 3 repeaters and one of my HF
> stations. Some 50 ft away is a old Hickory tree that's about 60 to 70 ft
> tall. Two years ago I received a lightning strike that destroyed the
> tree. No damage to the tower, any of the 12 antennas on the tower or any
> of the equipment in the two racks in the building. The tower and
> equipment was correctly and properly grounded. The tree wasn't.

A number of years ago, I got an induced strike on an untuned doublet that vaporized the copper out of 45 feet of window line from the doublet to the remote balun under the eaves of the house. Left a huge black mark on the side of the house.

None of my radio gear was hurt. It was all in the car. It was Sunday of Field Day, and I had come home to nap and hadn't unpacked my gear.

The doublet was unconnected. I believe I would not have taken any damage had the antenna been properly grounded at the time. Today I ground all my antennas that are not in use.

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Guy, K2AV

Re: Grounding negative side of power supply?

I had an end-fed 1/2 wave L (135 feet, 65 up and 70 out) which was at
DC ground at the base feedpoint and connected with three ground rods
in a ten foot radius. Lightning evaporated it. Grounding does NOT keep
it from being struck. However it did not continue to the house on the
coax, which was further grounded at the house entry point. I DID have
a 20 foot #4 bonding wire from the house entrance ground out to the
base tuning unit and those ground rods that ran parallel to the coax
most of the way.

73, Guy.

On Tue, Apr 20, 2010 at 10:14 PM, Bill Coleman <[hidden email]> wrote:

>
> On Apr 20, 2010, at 7:52 PM, Robert Mcgraw wrote:
>
>> At my shop sits my 100 ft tower for the 3 repeaters and one of my HF
>> stations. Some 50 ft away is a old Hickory tree that's about 60 to 70 ft
>> tall. Two years ago I received a lightning strike that destroyed the
>> tree. No damage to the tower, any of the 12 antennas on the tower or any
>> of the equipment in the two racks in the building. The tower and
>> equipment was correctly and properly grounded. The tree wasn't.
>
> A number of years ago, I got an induced strike on an untuned doublet that vaporized the copper out of 45 feet of window line from the doublet to the remote balun under the eaves of the house. Left a huge black mark on the side of the house.
>
> None of my radio gear was hurt. It was all in the car. It was Sunday of Field Day, and I had come home to nap and hadn't unpacked my gear.
>
> The doublet was unconnected. I believe I would not have taken any damage had the antenna been properly grounded at the time. Today I ground all my antennas that are not in use.
>
>
>
> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
> ______________________________________________________________
> Elecraft mailing list
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>
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>

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