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In writes:

[...]

Many yeards ago I read an article which stated that back in World War
One days President Wilson convened an advisory council composed of a
number of prominent Americans from different fields. Edison was a
member. Somebody suggested that Einstein would make a good addition to
the group. Edison's comment was something like "Somebody like Einstein
might be handy to have around in case somethimg needs to be figured
out."

w3rv

Sounds like an interesting story. No disrespect intended if I say that
it sounds apocryphal, though many credulous-sounding stories do
sometimes actually turn out to be true (see http://www.snopes.com for
the straight skinny on many of them). Perhaps the basic back-story is
true, but with one or more different players (see below).

This one caught my eye, as someone who has a passing interest in
American history from formal education in school, later personal reading
of biographies by David McCullough, Steven Ambrose, etc., and from
additional training that many Americans get: specifically, from watching
hundreds of episodes of the game show "Jeopardy" :-).

I was wondering if someone else with more expertise in the subject had
some additional insight. Googling around doesn't seem to demonstrate
that the story is true, nor does it demonstrate that the story is
untrue. One thing that makes me suspicious is that for these three men
(Wilson, Edison, Einstein) to have knowledge of one another in the way
that the story suggests, their timelines, particularly the periods
during which they were famous in the United States, would have had to
significantly overlap.

President Woodrow Wilson lived from 1856 to 1924 and served as President
from 1913 to 1917.

Thomas Edison lived from 1847 to 1931, and generally became famous as an
inventor after the invention of the phonograph in 1877.

Albert Einstein lived from 1879 to 1955, became well-known among
physicists sometime during his famous, and initially controversial,
research published from 1905 to 1915, won the Nobel Prize in 1921,
visited the U.S. shortly afterwards, and eventually became well-known
among most Americans (including Presidents) sometime after he emigrated
to the U.S. in 1932, certainly sometime during or after World War II.

Some points to ponder:

- An early 20th Century U.S. President like Wilson might have been
aware of American winners of the Nobel prize, but might he have been
made aware of a still relatively obscure German/Swiss physicist
before he left office in 1917, pre-Nobel?

- Even if we assume that the President was Warren Harding (who was
close to Thomas Edison, even camping out with him in Maryland during
his presidency:

http://www.ohiochannel.org/your_stat...&file_id=81864

Harding only served briefly from 1921 to 1923. A better match would
be Herbert Hoover, who clearly was aware of Albert Einstein:

http://www.presidency.ucsb.edu/ws/index.php?pid=22068

and served during the time that Thomas Edison was still alive:

http://teachpol.tcnj.edu/amer_pol_hi...mbnail341.html

- Hoover's successor, Franklin Delano Roosevelt (FDR), only became
president in 1933, two years after Edison died in 1931.

- Thomas Edison was a great inventor, but an individual without much
formal education. Would he have necessarily been aware of what was
going on in a theoretical academic field like Physics before 1917,
and before Einstein had even done recognized works in that field?
Recall that the General Theory of Relativity, published in 1915, was
not widely accepted until years later, his Nobel Prize was for the
Photoelectric Effect, and as a resident of one of the countries in
the Central Powers (opposing the U.S., France, and the UK during
WWI), his work would be censored from international publication
during most of Wilson's term, anyway:

http://en.wikipedia.org/wiki/Albert_...ral_relativity

- The only reference I could find to Albert Einstein and Thomas Edison
even just in communication with one another was this photograph from
1930:

http://www.topfoto.co.uk/gallery/einstein/default.htm

where Einstein telephoned Edison (from Germany) to congratulate him
on the 50th anniversary of the invention of the electric light bulb,
much later than Wilson's term of office.

So, the timelines of Wilson, Edison, and Einstein don't really match up
simultaneously. Nor do those of FDR match up with Edison, nor Wilson
with Einstein. Either the President would have to be someone like
Hoover or Harding, or the scientist would have to be someone else. At
the very least, Einstein couldn't really be considered a "prominent
American" until after he emigrated to the U.S. in 1932, and obtained
U.S. citizenship in 1940.

Ob Amateur Radio: Thomas Edison was a contemporary of Hiram Percy Maxim
(co-founder of the ARRL), who lived from 1869 to 1936, and is credited
with inventing the Maxim Silencer for firearms, and the automobile
muffler. Hiram's father, Hiram Stevens Maxim, invented the machine gun,
and was involved on the losing end of several patent disputes with
Edison over the incandescent light bulb.

- --
73, Paul W. Schleck, K3FU

http://www.novia.net/~pschleck/
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The National Electrical Code (NEC) specifies that there be two
grounding points for a residential system. That can mean either two
ground rods, six feet apart, connected to the panel with a continuous
loop of wire, or a single ground rod in cases where there is municipal
water, and the second ground source is the water main coming in, on
the road side of the meter. The gas line also needs to be grounded to
the panel.

In the main service panel, the grounding system is attached to the
same buss as the bare neutral coming in from the transformer. If your
shack is running off a sub-panel, it should be fed with four conductor
cable. In this case an insulated neutral is used and the bare (or
insulated, it doesn't matter in this instance) ground is connected to
a separate equipment ground buss. If your shack is in a separate
structure that has its own sub panel, it needs to be fed with three
conductor ground, the neutral is connected to the ground bar and a
ground wire from a single ground rod is connected to the same buss
(similar to the setup at the main panel). It sounds confusing as
written here, and it's even more confusing to read it from the NEC,
but I just had this out yesterday with my local inspector while going
over the fine points on a job.

All that NEC stuff is important to check to make sure you're setup is
electrically safe. As for station grounding, it's not usually a good
idea to use the electrical system ground rods for your RF grounds.
Your rig, tuner, amps, etc, should all be grounded to a single buss
with the shortest possible wires, then a large chunk of wire, #6 or
better, should run as directly as possible to a separate 8' ground
rod. If you have a tower, you should drive at least one 8 footer at
the base and ground it there. There's no limit to the number of ground
rods you can have for RF grounds, they're less than $10 from a
distributor and well worth the effort. I've heard of hams setting up
verticals with very minimal radials, just driving several ground rods.

But somewhere along the line somebody in the ham groups stated that
the National Electrical Code states that there shall be one and *only
one* grounding point per power drop and the neighborhood code cops and
the insurance companies reportedly get stiff about it.

The answer to that is that if there is more than one they must be
connected. The methods differ depending on the location of services in
the structures and around the property. An electrician following the
NEC would have done this during the installation and (hopefully) the
inspector would have signed off on it. Ground rods for RF equipment
SHOULD NOT be connected in any way to the electrical system ground
rods.

73
KC2PNF
Jon Dayton

BNB Sound wrote:
The National Electrical Code (NEC) specifies that there be two
grounding points for a residential system. That can mean either two
ground rods, six feet apart, connected to the panel with a continuous
loop of wire, or a single ground rod in cases where there is municipal
water, and the second ground source is the water main coming in, on
the road side of the meter. The gas line also needs to be grounded to
the panel.

Grounding the gas line here would be an exercise in futility. A metal
pipe goes into the ground just outside my home. It is three feet long.
It then connects to a plastic gas line which goes under U.S. Route 250
and runs to a gas meter about 100 yards away.


All that NEC stuff is important to check to make sure you're setup is
electrically safe. As for station grounding, it's not usually a good
idea to use the electrical system ground rods for your RF grounds.
Your rig, tuner, amps, etc, should all be grounded to a single buss
with the shortest possible wires, then a large chunk of wire, #6 or
better, should run as directly as possible to a separate 8' ground
rod. If you have a tower, you should drive at least one 8 footer at
the base and ground it there. There's no limit to the number of ground
rods you can have for RF grounds, they're less than $10 from a
distributor and well worth the effort.

That's a very, very bad idea. If your shack ground is not tied to your
electrical ground and a near miss strikes power lines, the shack ground
and your electrical ground will be at very different potentials. Your
radio gear will be right in the middle.


I've heard of hams setting up
verticals with very minimal radials, just driving several ground rods.

I've heard of it too, but it is another very bad idea. There is simply
no way that driven ground rods can substitute for a radial screen. They
are intended to do different things.

But somewhere along the line somebody in the ham groups stated that
the National Electrical Code states that there shall be one and *only
one* grounding point per power drop and the neighborhood code cops and
the insurance companies reportedly get stiff about it.

The answer to that is that if there is more than one they must be
connected. The methods differ depending on the location of services in
the structures and around the property. An electrician following the
NEC would have done this during the installation and (hopefully) the
inspector would have signed off on it. Ground rods for RF equipment
SHOULD NOT be connected in any way to the electrical system ground
rods.

That's simply incorrect and dangerous. I have connected my shack ground
to my electrical ground with some great big honkin' copper wire. You
may have as many different ground rods as you like. You should connect
all of them to a single point.

Dave K8MN

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In Paul W. Schleck " writes:

[...]

President Woodrow Wilson lived from 1856 to 1924 and served as President
from 1913 to 1917.

[...]

While true, it's also true that he served as President from 1917 to 1921.

:-)

Even in that sea of dates that I posted, I should have noticed that
Wilson was not a one-termer, and did serve through World War I Armistice
Day on November 11, 1918.

- --
73, Paul W. Schleck, K3FU

http://www.novia.net/~pschleck/
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Dave Heil wrote:

BNB Sound wrote:
I've heard of hams setting up
verticals with very minimal radials, just driving several ground rods.

I've heard of it too, but it is another very bad idea. There is simply
no way that driven ground rods can substitute for a radial screen. They
are intended to do different things.

Correct. RF "grounding" is so different from Power ground that it
shouldn't even be called the same thing. Good RF grounding can be had
without a direct connection to the earth, my radials are insulated wire
and don't have any wire exposure to the ground, so that they won't
corrode. (note that the antenna gets direct connection to ground through
the base.

It sounded freaky weird to me at first, but as I put in my radials over
several sessions (criteria being how long my poor abused knees could
stand it) I measured and adjusted the system each time, and it worked as
advertised. More radials = better grounding. The coil at the bottom of
my vertical required less and less inductance to match the system.

But it surely isn't a power ground, and given that the rf is absorbed
(right word) at or near the ground surface, those ground rods would only
be useful at that first foot or so.

- 73 de Mike N3LI -

wrote:
On Nov 27, 8:46 pm, Dave Heil wrote:
James Barrett wrote:
Does it really matter if my equipment is ground to the house ground or
should it really be connected to its own external ground? And if/when
I ground to guard against lightning strikes, would I use that same
external ground or go with yet another external ground?
I'm still doing my research, but figured it couldn't hurt to ask.
Jim,

You'll see numerous references on the web to "single point ground." It
is very, very important stuff. I got nailed on this stuff back in
August, 2003. Here's how it played out:

We had a violent thunderstorm early one morning about 7 A.M. Suddenly
there were three near strikes (simultaneous lightning and thunder)
within a ten second time frame. In addition to telephones, computers
and home entertainment equipment, my four month old Ten-Tec Orion and
numberous shack accessories were zapped. My house ground is a single 8
foot copper plated ground rod. The lightning ground for the shack was
an identical ground rod driven about thirty feet away from the house ground.

When the strikes conducted a surge into my home via the power lines, all
three wires had very high voltage on them. The shack ground was still
at its usual potential (0). The house ground was elevated to high
voltage. There was a potential difference between the shack ground the
the house ground. That potential quickly equalized inside my equipment.

Ten-Tec reported that six boards inside the Orion had their ground
traces evaporated.

For a shack ground, you want the shortest possible distance between your
rig and earth. The house ground will be as close as possible to your
electrical service entrance. If, like me, you have to use two ground
rods, you need to bond the two of them together with a big, fat wire so
that the two can never be at different potentials.
If you have a tower, I'll assume that you have at least one 8 foot
ground rod driven at its base. Bond your coaxial cable sheaths to the
rod at the tower. The sheaths should also be bonded to your shack ground.

Dave Heil K8MN

This whole topic area seems to be eternally confused and confusing and
I'm in the parade of the confused. On a common sense basis I
absolutely agree with your connecting the station grounds to the
'lectric service entrance ground for the reasons you've stated.

But somewhere along the line somebody in the ham groups stated that
the National Electrical Code states that there shall be one and *only
one* grounding point per power drop and the neighborhood code cops and
the insurance companies reportedly get stiff about it.

So is it legal to connect a phalanx of ham station ground rods to the
service entrance ground?? Or not.


w3rv


What the code enforcement types get vexed about is were you have two
different Grounding Electrode Systems (GES) that are not bonded together
into a single system. So if you have one concrete encased electrode in
your tower base, another concrete encased electrode in your homes
footer, and a driven rod array electrode just outside the radio room
wall and you do not bond them together into a single GES that is a code
violation. It is also a code violation to connect any conductor that
carries power and light current to ground at any point in the wiring
system that is not at the Service Disconnecting Means (SDM). The SDM is
the first switch, breaker, or fused pull out that can be used to
disconnect the ungrounded current carrying conductors of the wiring
system from the service entry conductors. In most homes this is the
main breaker or the main fuse pull out. The code name for the white
wire in North American wiring practice is the "Grounded Current Carrying
Conductor." In many cases it is also the neutral conductor but that is
not always the case. It is that white wire that most of us call the
neutral; albeit sometimes mistakenly; that must be connected to the GES
at one and only one point. That point is the portion of the service
entrance grounded conductor that is between the splices that connect it
to the utility company's conductors and the SDM.

A practice that was very popular in the computer industry was to ground
the computer equipment power supplies of main frame computers to a new
and separate grounding electrode at the computers location. Connecting
that ground back to the power service ground was carefully avoided on
the belief that doing so would cause ground loops on the signal circuits
between the main frame and the associated terminal equipment. Some self
qualifying authorities recommended the same approach for radio
equipment. That left the earth between the two electrode systems as the
only return path for current faulting to ground at the improperly
isolated ground equipment. With the resistance to earth of most driven
rod electrodes being over fifty ohms the series resistance of such a
fault current pathway was often over a hundred ohms. Such a high
impedance would limit the fault current flowing back to the utility
transformer from whence it came to a flow too small to trip the Over
Current Protective Device (OCPD) protecting the faulted circuit. You
then have a situation in which all of the exposed conductive parts of
the radio or computer equipment is energized at 120 volts relative to
earth or any body that will behave as the earth does electrically.
Since it only takes about a third of an ampere to kill a human being the
user could be electrocuted without ever tripping the OCPD. Because the
danger to life was of a greater concern to code authorities then the
difficulties caused by ground loops on signal lines the electronic
engineers lost that war with the electrical engineers and the rule
forbidding separate grounding electrode systems survived the attempts to
remove it from the nations electrical codes.

The good news for us as amateur radio practitioners is that what is safe
is also good operating practice. By bonding all of our grounding
electrode systems together into a single system we get a better ground
for most purposes and we greatly decrease the likelihood of equipment
damage or operator injury / death.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison