Station With Center-Fed Dipole - Best Grounding Technique?
 

On Wed, 06 May 2009 02:34:45 +0200, noname wrote:

panel ground. Can YOU find that ground?


I don't understand your question. The radio chassis is grounded to the
wall outlet. The overall house wiring was recently inspected, with the
grounding checked at that time. It was a thorough inspection which
also included a device plugged into most outlets to check the wiring.
Given that, I don't really know what I'm supposed to find and why.

Hi Stewart,

If you are going to add a ground, it has to go to the ground electrode
- it is called service ground. That is located in very close
proximity to the fuse box - it is called the service panel. Close
inspection (by you) should reveal it. It may be a wire tied to a cold
water feed from the city services.

So, by this explicit statement, your "balanced" antenna
has been unbalanced at the rig (which only further enforces
the unbalance by virtue of the coax connection).


I guess so. Actually, I don't really know. The radio was manufactured
with the chassis grounded to the wall outlet and the antenna was
designed by it's manufacturer to work properly with 50 ohm coax feed
connected (I would assume) to a radio like this. What impact that has
on balanced versus unbalanced is beyond me, and the same is true for
what exactly you want me to do about it.

A purist's balanced antenna is connected to a twin lead, or open wire
pair. This transmission line goes to the purist's special tuner with
a balanced connection. Many cheap tuners pretend to offer this
option. Expensive tuners the purists use pretend to do it too. At
some point, one of those two wires (if you were using twin lead) would
go to the chassis. This would make it unbalanced, and this unbalance
would be cast back into the antenna making it unbalanced. There are
tuners that do it right, but you have to look under the hood and
verify their claims.

Using a coax means you are using a conventional connector with a
collar (bayonet style or screw type) that connects directly to the
chassis. BINGO! Your system is unbalanced. But it was unbalanced
before it got there, and the connection only enforced it. The coax
offers what is called the "third wire" to the dipole with its shield
(the shield exterior is a separate circuit to its interior circuit).
When you use a coax with a dipole, you are making it a tripole, with
one leg of indeterminate length. You can reduce the third circuit
path effect through choking.

If you cared about the state of balance, then you can take steps to
reachieve balance. One is to choke the feed point at the antenna, and
then choke it again a quarter wave down from that point. You can (as
suggested by Jim) choke the ground as well. You can (as suggested by
MFJ) choke the transmitter end of the coax. Each brings an additional
degree of isolation, and attempts to bring balance. Unfortunately,
balance is also a function of what physical distance and bulk
relations each arm of the antenna sees. Nature and homes rarely exist
with perfect symmetry (another name for balance) to serve an antenna.

You could add a chimney stack to the other end of the house, and
rearrange furniture (and occupants) inside to help, but life is short.
Got trees? If you are operating 80 meters, anything within 100 feet
is fair game for the balance sheet.

As for impact, there is every chance you don't need to do anything but
insure a good safety ground. If your chassis bites you during
transmission, then, yes, add some chokes (see thread). If your
antenna picks up signals from directions you had pointed the antenna
away from, then, yes, add some chokes (see thread). If you cannot
tune the antenna on some bands, maybe (just maybe), add some chokes
(see thread).

73's
Richard Clark, KB7QHC

Station With Center-Fed Dipole - Best Grounding Technique?
 

Howard Lester wrote:
"Tom Ring" wrote

He's feeding it with coax, so it's not just a good idea, it's required.

The antenna is balanced, the feedline is not. He stated the feedline is
RG-8X.

I know that, and just because it's balanced to unbalanced, it's not
*required.* The antenna system can work just fine without one. In some
cases, at least according to the late Lew McCoy, it can do more harm than
good. If the antenna system is inherently unbalanced due to one leg being,
say, in greater proximity to metal and other objects, then I would consider
using some kind of balun or choke system.



Well, I'm not going to argue with someone who thinks that placing a
balun between an unbalanced feed and a balanced load could ever possibly
do more harm than good.

It would be a utter waste of time.

tom
K0TAR

Station With Center-Fed Dipole - Best Grounding Technique?
 

Howard Lester wrote:
"Tom Ring" wrote

He's feeding it with coax, so it's not just a good idea, it's required.

The antenna is balanced, the feedline is not. He stated the feedline is
RG-8X.

I know that, and just because it's balanced to unbalanced, it's not
*required.* The antenna system can work just fine without one. In some
cases, at least according to the late Lew McCoy, it can do more harm than
good. If the antenna system is inherently unbalanced due to one leg being,
say, in greater proximity to metal and other objects, then I would consider
using some kind of balun or choke system.



Sorry, I forgot to add

PLONK!

tom
K0TAR

Station With Center-Fed Dipole - Best Grounding Technique?
 

Some of the participants here might find
http://eznec.com/Amateur/Articles/Baluns.pdf interesting.

Roy Lewallen, W7EL

Station With Center-Fed Dipole - Best Grounding Technique?
 

"noname" wrote in message
...



Again, this is an entirely a new setup which has not been installed
yet. What I'm seeking here is some input on the best way to do that.
I'm fairly familiar with the basics of dipole antennas, but hoping for
some solid advice from those with a lot more experience than my own.


Matching issues aside, common thinking on the balun issue is that it greatly
attenuates current on the outside of the coax.

In certain rare cases, I suppose such current could be a good thing, giving
additional radiation in a desired direction, but I'd never try to predict it
or control it. Use the balun because the benefits of keeping the RF "out
there" are considerable: Less TVI, no false ringing of your telephones, less
squawking from your computer speakers, no computer mouse or keyboard doing
its own thing, no cable modem resetting itself, no RF burns on your
fingertips (although there are other ways to get them, hi-hi).

The lack of a balun may not cause every listed malady, above, but that's a
short list of some that I have caused or witnessed from a quick-rig antenna
that didn't have a balun. They went away when one was installed.

Station With Center-Fed Dipole - Best Grounding Technique?
 

Tom Ring wrote:

Well, I'm not going to argue with someone who thinks that placing a
balun between an unbalanced feed and a balanced load could ever possibly
do more harm than good.

That's because you are calling it a dipole and assuming it is a balanced
antenna. In reality, it's a quarter wave sideways vertical wire antenna, with
a single quarter wave radial at the feed point.

See, now it all makes sense. :-)

Or a quarter wave end fed horizontal antenna with a single tuned feed
point radial.

Not only that, I wonder if I can patent them, and sell them via a web site
for big bucks.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

Station With Center-Fed Dipole - Best Grounding Technique?
 

Jim Lux writes:

dave wrote:
Jim Lux wrote:


Do you use a balun at the antenna
feedpoint? How do you tune the inverted-V?

Good RF chokes on the coax at the feedpoint and at the point of
entry would go a long way to eliminating any "RF in the shack"
problems. A couple 2.4" 31 mix cores with half a dozen turns on
them, for instance.

Whether the V is tuned or not won't have any effect on RFI or grounding.

A BalUn would help a lot.

Balun/choke.. tomato, tomato.. they're really all the same thing.
Keep the RF off the outside of the coax.



Since we are sticklers for the NEC, Homey needs a #6 wire from where
the transmission line enters the dwelling to an 8' copper clad rod
driven into the earth, as close as practicable.

Turns out he's located in Germany, so U.S. codes aren't particularly
relevant. If anything, German codes are probably stricter. But almost
certainly different.

Jon LA4RT


The communications system (be it CATV, net powered broadband, amateur,
etc.) would need to be bonded to any of the usual things that form the
grounding/bonding system,e.g, one could "ground" through the metal
conduit.

A ground rod is, of course, not recommended in the current codes as a
made electrode, and in any case, the code doesn't necessarily require
a specially installed ground for this purpose. If you DO install
another ground, then it has to be bonded with AWG #6 copper (or
bigger) (can't use the conduit)

Telephone has different rules. Must have electrode/grounding means as
close as practicible to point of entrance, and the ground wire has to
be AWG14 or large, insulated, in as straight a line as possible.

Metal structure supporting outdoor antenna systems have to be grounded
with AWG10 or bigger copper, AWG8 aluminum, or AWG17 copperclad steel,
straight line. (the size requirement is for mechanical strength, not
conductivity, which is why the copperweld(r) can be smaller)

So you have these weird situations where the phone protection block
has to be connected with AWG14 insulated to a grounding electrode as
close as practicible, but then, because of the "bonding of electrodes"
rules, you have to connect that electrode to the "house ground" with
nothing smaller than AWG6.

CATV is even different.. grounding block for drop has to be grounded
to an electrode close to block and an *insulated* AWG14 or bigger run
to bond with the rest of the house's grounding system.


This sort of thing is why most ham installations aren't "code
compliant"... heck, you could go insane trying to wend your way
through the thicket of rules for the NEC. And that doesn't even begin
to get into the transient suppression guidelines and/or NFPA 780
lightning protection rules.

Station With Center-Fed Dipole - Best Grounding Technique?
 

Roy Lewallen wrote:
Some of the participants here might find
http://eznec.com/Amateur/Articles/Baluns.pdf interesting.

Roy Lewallen, W7EL

Thanks Roy. Read it a while ago, but good to get a refresher.

tom
K0TAR

Station With Center-Fed Dipole - Best Grounding Technique?
 

Geoffrey S. Mendelson wrote:

That's because you are calling it a dipole and assuming it is a balanced
antenna. In reality, it's a quarter wave sideways vertical wire antenna, with
a single quarter wave radial at the feed point.

See, now it all makes sense. :-)

Or a quarter wave end fed horizontal antenna with a single tuned feed
point radial.

Not only that, I wonder if I can patent them, and sell them via a web site
for big bucks.

Geoff.


You need to have a chat with Billy Mays. If he hasn't made it to
networks in that part of the world, you're lucky.

HI I'M BILLY MAYS FOR THE HYPER-Q ANTENNA!!!!

THIS PATENTED DESIGN OUTPERFORMS EVEN A DIPOLE!!!! ....

Station With Center-Fed Dipole - Best Grounding Technique?
 

Sal M. Onella wrote:
In certain rare cases, I suppose such current could be a good thing, giving
additional radiation in a desired direction, but I'd never try to predict it
or control it.

The Carolina Windom folk advertise feedline
radiation as an advantage over other antennas
and charge extra $ for it. :-)
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Station With Center-Fed Dipole - Best Grounding Technique?
 

What if you use a coax with two shields, one shield for chassis ground
which is the coax connection and the outer shield for earth/ground?
Yes, there could be a ground loop but the nearest ground to a strike/
antenna is probably the best protection

You'll still need to deal with RF currents flowing on the outside of the
coax (and also potentially between inner and outer shields).

A good transient suppression scheme at the entry point deals with the
overvoltages from lightning, power lines falling on your antenna, etc.

The challenge is in protecting a sensitive receiver front end, while not
introducing other problems: if the receiver burns out at 1Volt, a clamp
at 300V isn't going to save the front end, although it will keep the
radio from catching on fire. A diode clamp to the supply rails or
similar will save the front end, but will almost certainly result in IMD
issues with strong input signals. Sometimes, the front end just has to
be the sacrificial "fuse", so you want to make sure that it's a cheap &
replaceable part that suffers.

Station With Center-Fed Dipole - Best Grounding Technique?
 

Jon Kåre Hellan LA4RT wrote:
Jim Lux writes:

dave wrote:
Jim Lux wrote:


Do you use a balun at the antenna
feedpoint? How do you tune the inverted-V?
Good RF chokes on the coax at the feedpoint and at the point of
entry would go a long way to eliminating any "RF in the shack"
problems. A couple 2.4" 31 mix cores with half a dozen turns on
them, for instance.

Whether the V is tuned or not won't have any effect on RFI or grounding.
A BalUn would help a lot.
Balun/choke.. tomato, tomato.. they're really all the same thing.
Keep the RF off the outside of the coax.


Since we are sticklers for the NEC, Homey needs a #6 wire from where
the transmission line enters the dwelling to an 8' copper clad rod
driven into the earth, as close as practicable.

Turns out he's located in Germany, so U.S. codes aren't particularly
relevant. If anything, German codes are probably stricter. But almost
certainly different.

Jon LA4RT


Yes indeed. It's not like there's any universal consistency in the U.S.
either.

I recommend IEEE Std 1100 for people who really care. (and it is an
international standard, so it addresses most of the regulatory issues
regardless of location)

Station With Center-Fed Dipole - Best Grounding Technique?
 

On May 6, 11:36*am, Jim Lux wrote:
What if you use a coax with two shields, one shield for chassis ground
which is the coax connection and the outer shield for earth/ground?
Yes, there could be a ground loop but the nearest ground to a strike/
antenna is probably the best protection

You'll still need to deal with RF currents flowing on the outside of the
coax (and also potentially between inner and outer shields).

A good transient suppression scheme at the entry point deals with the
overvoltages from lightning, power lines falling on your antenna, etc.

The challenge is in protecting a sensitive receiver front end, while not
introducing other problems: *if the receiver burns out at 1Volt, a clamp
at 300V isn't going to save the front end, although it will keep the
radio from catching on fire. *A diode clamp to the supply rails or
similar will save the front end, but will almost certainly result in IMD
issues with strong input signals. *Sometimes, the front end just has to
be the sacrificial "fuse", so you want to make sure that it's a cheap &
replaceable part that suffers.

Let me try again and put it another way. What if:
The transmission line is a two parallel wire system.This is enclosed
in one sided metalized mylar isolated shielding Total covered with
insulation and wire netting for true ground ? All of the above buried
in ground

Station With Center-Fed Dipole - Best Grounding Technique?
 

Art Unwin wrote:
On May 6, 11:36 am, Jim Lux wrote:
What if you use a coax with two shields, one shield for chassis ground
which is the coax connection and the outer shield for earth/ground?
Yes, there could be a ground loop but the nearest ground to a strike/
antenna is probably the best protection
You'll still need to deal with RF currents flowing on the outside of the
coax (and also potentially between inner and outer shields).

A good transient suppression scheme at the entry point deals with the
overvoltages from lightning, power lines falling on your antenna, etc.

The challenge is in protecting a sensitive receiver front end, while not
introducing other problems: if the receiver burns out at 1Volt, a clamp
at 300V isn't going to save the front end, although it will keep the
radio from catching on fire. A diode clamp to the supply rails or
similar will save the front end, but will almost certainly result in IMD
issues with strong input signals. Sometimes, the front end just has to
be the sacrificial "fuse", so you want to make sure that it's a cheap &
replaceable part that suffers.

Let me try again and put it another way. What if:
The transmission line is a two parallel wire system.This is enclosed
in one sided metalized mylar isolated shielding Total covered with
insulation and wire netting for true ground ? All of the above buried
in ground


Well, sure.. (leaving aside the problems of running a two wire line
inside a tube) At some point, though, something's got to emerge from
the shielded cage or it's not a electric dipole antenna. (One can make
a totally shielded loop antenna, of course)

Station With Center-Fed Dipole - Best Grounding Technique?
 

noname wrote:
Thanks for the replies, Dave, Rick, and Jim. Since my ideas didn't go
over so well, perhaps it's best to just describe my setup and then
listen to any suggestions. Since I'm not an electrical engineer, do
try to keep things simple.

As I said earlier, the radio and speaker are both connected to the
house ground through their power cords. I've also installed an
inverted V dipole in the back yard (the only place it will fit). The
center (feedpoint) of the antenna is attached to the roof on the
second floor (about twenty feet above the ground) and the two ends run
out to the two corners of the backyard. That's the best I can
accomplish given local antenna restrictions.

My house is located on a hill with a top floor entrance and living
area. Below that is another floor level with the backyard, with a
basement below that.

The radio will be located in the living room on the top floor, again
one floor above the backyard. The coax (RG-8X) will run out a window
on the second floor to the center (feedpoint) of the antenna attached
to the roof just outside (a run of roughly 15-ft).

Now, where (if any) should I add grounding to that setup? I was going
to add a lightning arrester to the coax just before it enters the
house (fed into two ground rods), but will forego that since none seem
overly thrilled about the idea.

By the way, a Yeasu technician once recommended salting ground rods to
resolve a poor grounding situation at the time, so I've been doing
that ever since (can't hurt), especially during the dry summer months.
Adding water is pretty obvious, so didn't think I needed to spell that
out, Dave.

stewart / w5net

Dave

I'm not an engineer either but I have installed ridge top communications
shelters from the Argentine Pampas to Alaska without having lightning
caused down time for the communications equipment that the shelters
contained. You need a single point of ground connection in the shack.
One of the best ones to have is an antenna entry bulkhead made of some
stout aluminum or copper plate. You then run all of the connections
that serve your equipment through or past that bulkhead. You also mount
all of your protectors on or at that bulkhead. From the outside of the
bulkhead you run a ribbon conductor down to the Grounding Electrode that
you install as close to directly below the bulkhead as you can.

If the electrode will be driven rods then buy yourself several rod
couplers to permit you to drive the rods to a depth below the permanent
moisture level. The driving is best accomplished by renting an electric
demolition hammer and a ground rod cup. You will need some means to
measure the grounding electrode resistance to earth. You can rent a
three pole or four pole ground impedance tester or a much easier to use
clamp on ground loop impedance tester. You want the total impedance of
the Grounding Electrode System to be less then twenty five ohms and the
lower you get it the better off you are. If you drive four or five rods
on top of each other then you will have reached between thirty two and
fifty feet into the earth. In most cases you will strike hard pan or
rock before that depth and thus will have to drive additional rods. If
your first stacked rod does not get you down to twenty five ohms or less
you just drive a second stacked rod at least the length of the first rod
away from the first rod. Once you have the Grounding Electrode down to
twenty five ohms or less you bond it to the electrical grounding
electrode using a number four or larger copper conductor that is run
entirely outside the builidng.

For best protection you would run the bonding conductor in the form of a
partial ground ring consisting of a number two copper conductor buried
in trench that is thirty inches deep and runs from the one electrode to
the other around the outside of the home.

If your home is new enough to have a concrete encased electrode for it's
power ground then it may be possible to bond to it by bonding to one end
of any steel beam that was used in the floor support at the basement
ceiling. If the electrician was competent the beam will be bonded to
the concrete encased electrode. You will have to check carefully to
assure that it is so bonded.

It is terribly unlikely that your home has a true Ufer ground because
constructing one involves a mesh of half inch or larger rebar that is
continuous throughout the basement floor and foundation footers with all
junctions double tied and one piece of rebar turned up out of the floor
at the location of the electrical service equipment.

If your not willing to do all of that; and most hams are not; you will
have to choose how much to do. The bulkhead, a one inch braid Grounding
Electrode Conductor, two eight foot driven rods at least their own
length apart, and the number four bonding conductor to bond those to the
electrical service ground is the minimum for lightning protection.
Anything less is a feel good waste of time.
--
Tom Horne

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

Station With Center-Fed Dipole - Best Grounding Technique?
 

dave wrote:
Jim Lux wrote:


Do you use a balun at the antenna
feedpoint? How do you tune the inverted-V?

Good RF chokes on the coax at the feedpoint and at the point of entry
would go a long way to eliminating any "RF in the shack" problems. A
couple 2.4" 31 mix cores with half a dozen turns on them, for instance.

Whether the V is tuned or not won't have any effect on RFI or grounding.

A BalUn would help a lot.

Since we are sticklers for the NEC, Homey needs a #6 wire from where the
transmission line enters the dwelling to an 8' copper clad rod driven
into the earth, as close as practicable.



and bonded from their to the electrical service grounding electrode
system with a number four or larger conductor.
--
Tom Horne

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

Station With Center-Fed Dipole - Best Grounding Technique?
 

Jim Lux wrote:
Jon Kåre Hellan LA4RT wrote:
Jim Lux writes:

dave wrote:
Jim Lux wrote:


Do you use a balun at the antenna
feedpoint? How do you tune the inverted-V?
Good RF chokes on the coax at the feedpoint and at the point of
entry would go a long way to eliminating any "RF in the shack"
problems. A couple 2.4" 31 mix cores with half a dozen turns on
them, for instance.

Whether the V is tuned or not won't have any effect on RFI or
grounding.
A BalUn would help a lot.
Balun/choke.. tomato, tomato.. they're really all the same thing.
Keep the RF off the outside of the coax.


Since we are sticklers for the NEC, Homey needs a #6 wire from where
the transmission line enters the dwelling to an 8' copper clad rod
driven into the earth, as close as practicable.

Turns out he's located in Germany, so U.S. codes aren't particularly
relevant. If anything, German codes are probably stricter. But almost
certainly different.

Jon LA4RT


Yes indeed. It's not like there's any universal consistency in the U.S.
either.

I recommend IEEE Std 1100 for people who really care. (and it is an
international standard, so it addresses most of the regulatory issues
regardless of location)

Is there anyway to read that standard without spending serious money.
--
Tom Horne

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