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.

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)

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

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)

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

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

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