Hello

I have my shack on the second floor, about 8 meters above ground. I am going
to use a dipole antenna for 20M
Should I use the water pipe system as ground, or should I use a thick wire
on the housewall down to a ground rod?
I fear that the wire down to the ground rod may emit unwanted RF (have read
that somewhere).


Regards
Ruben

"Ruben Undheim" wrote

I have my shack on the second floor, about 8 meters above ground. I am
going
to use a dipole antenna for 20M
Should I use the water pipe system as ground, or should I use a thick wire
on the housewall down to a ground rod?
I fear that the wire down to the ground rod may emit unwanted RF (have
read
that somewhere).

Hi Ruben, sounds like three stories above ground, two stories would be 4
meters even if a 1 meter+ raised foundation was included. At any rate, a
dipole is a complete antenna that does not use an RF ground or counterpoise.
Transceiver mismatches will place high SWR on the feedline, not an RF ground
should you install one anyway. If you later add some kind of longwire or
other voltage-fed antenna then an RF ground would be important. You could
use 12" wide 20 ga copper flashing (available at roofing companies) to make
a workable ground from your elevated shack location. Anything less would
have incredibly high impedance due to the distance to earth ground. Your
dipole antenna feedline should enter the building at ground level, and the
coax shield should be grounded there before coming "up" into the shack.
There will remain a high potential between your shack equipment and the
earth ground no matter what kind of ground you attempt at that height. The
12" wide copper strap connection would just be the lowest potential you
could achieve, water piping or any solid wire size would not even come
close.

Best regards,

Jack Painter
Virginia Beach VA

I have my shack on the second floor, about 8 meters above ground. I am
going
to use a dipole antenna for 20M
Should I use the water pipe system as ground, or should I use a thick wire
on the housewall down to a ground rod?
I fear that the wire down to the ground rod may emit unwanted RF (have
read
that somewhere).

======================================

One of the advantages of a dipole antenna is that it doesn't need a ground
connection. There's nowhere to connect one.

The transmtter does need a ground and it usually obtains one from the
domestic 110-volt power socket.

But a much better ground can be obtained from the nearest domestic metal
water pipe or central heating system which eventually finds its way to the
incoming water main.

Two separate well-spaced ground connections, running in different directions
from the transmiter to different parts of the plumbing system are better
still. There is usually a threaded bolt with a wing nut at the rear of the
transmitter for connecting to ground wires.

A wire down the wall to a single ground rod makes a very poor ground. It is
worse than the connection to the 110-volt power socket. The rod is no
better than a shallow buried wire of about the same length. It is only of
use when there's nothing else available.

Grounding wires need be no larger than 16 or 12 gauge. Think in terms of
mechanical durability and reliability.

All wires in the vicinity of a transmitting antenna pick up and re-radiate
energy or transfer it somewhere else. It is of low level, usually
imperceptible and nothing to worry about.

Only when connected directly to an antenna to form part of the radiating
system will relatively large amounts of power find its way along wires to
where its not wanted. Something is usually seriously wrong if you should get
small harmless burns on the lips when using the microphone with a Tx power
of 100 watts or less.

There are a score of different ways in which things can happen. All are
curable. Most likely you will never be afflicted. No need to do anything
until something actually occurs.

It's very rare for earth wires to re-radiate anything that is harmful or
interferes with anything or is even detectable. Since 99 percent of
radiation comes from the antenna that's where most of the interference in or
around your house originates - if you should get any.
----
Reg

On 3 Nov 2004 13:16:53 +0200, "Ruben Undheim"
wrote:
Should I use the water pipe system as ground, or should I use a thick wire
on the housewall down to a ground rod?

Hi Ruben,

The water pipe is better, a ground rod is OK. For a balanced system,
ground's only use is for AC safety (to protect YOU).

I fear that the wire down to the ground rod may emit unwanted RF (have read
that somewhere).

As you are using a dipole, this unwanted radiation will occur only if
it is unbalanced. The radiation comes from "Common Mode" current.
"Common Mode" current is the difference in the two currents in each
half of the system that is unbalanced. Dipoles are balanced designs,
but not always balanced installations.

How can you tell when you have an unbalanced system? This is not
easy, OR if it is easy, it is a real problem.

One SWR reading does NOT indicate an unbalanced system. One SWR
reading does NOT indicate a balanced system.

The most obvious sign of "Common Mode" current occurs when your
transmitter acts odd by being difficult to tune, folding back its
power, or you can actually feel the sensation of current on bare metal
(like connector shells or a chassis). A minor sign of "Common Mode"
current is receiving signals on your dipole that should be in its
null. This last sign may even be a preferred condition, thus subtler
signs may go unnoticed.

What this means is that "Common Mode," or system unbalance, or ground
wire radiation may not be a problem even if it exists.

73's
Richard Clark, KB7QHC

Ruben, some corrections from:
"Richard Clark" writing:
Ruben Undheim" wrote:
Should I use the water pipe system as ground, or should I use a thick
wire
on the housewall down to a ground rod?

Hi Ruben,

The water pipe is better, a ground rod is OK. For a balanced system,
ground's only use is for AC safety (to protect YOU).

About the worst advice ever given, offering a water pipe in a second or
third story structure as an AC safety ground. First, unless you can verify
that the cold water supply in your structure is a bonded grounding electrode
conductor (and it probably is not), it must not be used for any kind of
electrical safety connection. Secondly, the AC circuit breakers that are
designed to protect your life by limiting the time-frame of a current
overload or neutral-sensing return voltage deficit cannot do so if you
modify the circuit path. This is dangerous even if the ground is as poor as
you would achieve from the elevated potential of your second or third story
flat. Only the bonding of all shack equipment, at least some of which would
be directly connected to the AC mains would provide additional electrical
safety. Grounding does NOT provide electrical safety, bonding does. It was a
typical "unbalanced amateur's response" to tell you otherwise. In an
equipment fault event, you could easily be killed by the current diverted to
a separate station ground if the equipment was not properly bonded first.

Best regards,

Jack Painter
Virginia Beach

Ruben Undheim wrote:
"Should I use the water pipe system as a ground, or should I use a thick
wire dowen to a ground rod?"

A 20M dipole needs no RF ground. It may get a lightning surge in search
of ground, a path to the earth.

To dissipate the surge to earth it is advantageous to use the same path
as the radio power supply takes to earth, not to create a big potential
difference within the radio.

As the power service to the radio may have a high RF impedance, which
would also oppose a surge, it is a good idea to also connect the thick
wire down to a ground rod.

Arc-gaps between the antenna feeders and the radio case may encourage a
surge to take the direct path to earth. The radio case must also be
connected to the electrical ground and the new ground rod at this point
(perhaps your shack).

All earth grounds must be connected together using approved connectors
to satisfy most electrical codes and to avoid differences of potential
between earth connections. Voltages and currents can be so large that
solder can melt. Welding or specified connectors are required.

If lightning takes the direct route to the earth via the arc-gaps, there
will be less stress on the electrical system.

Best regards, Richard Harrison, KB5WZI

Thanks for all the help! It feels good to clear things up!

Regards
Ruben


"Ruben Undheim" skrev i melding
...
Hello

I have my shack on the second floor, about 8 meters above ground. I am
going
to use a dipole antenna for 20M
Should I use the water pipe system as ground, or should I use a thick wire
on the housewall down to a ground rod?
I fear that the wire down to the ground rod may emit unwanted RF (have
read
that somewhere).


Regards
Ruben