Station Ground

Station Ground

Related Pages:

Antenna Grounds

My Contesting and
Boatanchor Room

Antenna System and
my house station

Consumer Gear

Ground Systems

House ground layouts

Lightning

Rohn 65G

RF In Station
Equipment

2nd Floor Grounding

Rumor has station equipment or desk grounds improving reception and
transmission, and reducing TVI or RFI. Some even think filters divert harmonics
to ground, where the ground absorbs unwanted signals. Like many things heard,
there is an element of true results behind scientific folklore.

In early radio installations,
single-wire feeders were common. Even after WWII, when coaxial cable became
common, very few systems used baluns. As a result, early installations
frequently had very high levels of RF on station wiring and equipment cabinets.

Early equipment did not have a safety ground. USA house wiring was absent the
round ground pin, having only a hot and neutral in 110 circuits, and a neutral
and two hot leads in 220 applications. Many pieces of gear, since there wasn’t a
safety ground connection on plugs and cord, depended on a ground rod for safety.
Manuals admonished users to “always attach an earth ground” to a ground terminal
on equipment.

Eventually line voltage increased, as did safety. Line voltage increased to a
nominal 117/234 volt with an isolated safety ground (grounded only at the fuse
box). Eventually, voltage became 120/240 with typical voltages reaching 125/250
during times of light load. We now have 120/240 in the USA, not 110 or 220
volts. Most equipment is now double insulated, or has a three wire cord with
safety ground.

What a Station or Desk Ground Can and Cannot Do

Effects on Signal Reception or Transmission

Even modern RF systems might have installation or design defects. These defects can
cause excessive RF current to flow on wires and cables entering the house.
Currents like this are called
common mode currents, because the current flows
without a close-by countering current. For example, a perfectly functioning
transmission line has exactly equal and opposite direction currents one each
close spaced conductor. This cancels distant radiation, and confines current to
the inside of the transmission line. If an antenna
or tower system has common-mode current
problems, caused by
a faulty design or
installation, a
ground can help
reduce common mode
noise reaching the
antenna. This is
really from an
antenna flaw, and
not from the
“reflection of
signals”.

In a case with unwanted common mode currents, a station or equipment ground
can also decrease TVI or RFI. The ground might do this by giving unwanted
current someplace harmless to flow, keeping RF out of power lines, CATV lines,
and telephone lines.

A station ground can also keep RF currents out of lossy media, by providing a
low resistance path, if unwanted antenna currents are appearing on station
equipment or cables.

Vertically polarized signals propagate along the earth with much less
attenuation than horizontally polarized signals.
A ground screen,
counterpoise, or
ground radial system
below an antenna
can reduce local
noise sensitivity by
reducing the
antenna’s response
to local noise. This
would apply only to a
horizontally
polarized antenna,
because earth losses allow increased levels of polarization
tilt. Lossy ground can increase
vertical
polarization response
of horizontally
polarized antennas.
Ground rods have no
effect on this, any
improvement
requires something
that actually covers
the lossy earth
under the
horizontally
polarized antenna.

A station ground might……

• Mask antenna installation or feed line problems
• Allow use of single wire feeders brought into the station, like a
  longwire or Windom antenna
• Improve lightning safety and reduce electrical shock hazard 

A station ground will
NOT…..

• Help
  reception or transmission, or RFI or TVI, in a properly working station with
  properly functioning transmission lines
• A
  ground will not
  reduce the chances
  of or number of lightning
  strikes

This is a typical
amateur installation:

Unless we have a
tower that is tall
compared to
surrounding
structures, or
unless we are
fortunate enough to
have
underground
utilities, lightning
most often
strikes utility
lines. Even when
heights of utility
lines and towers are
comparable, utility lines
offer a much
wider-area
target, so they get hit much more often.

Many amateur
radio installations
have an independent
radio-room ground rod installed just outside
the radio room.
Station ground rods that are
not bonded to the
power mains ground
outside the house
can, and often do,

increase chances of
equipment damage. We should never use an independent ground rod or rods just
outside the station as a station safety ground.

In this poor but common layout:

Lightning
surges flow from E into the
service drop and house
entrance (D).

A very small portion of
surge is
diverted into the
fairly high
resistance entrance ground
rod (C).

The station ground and “electrical mass” of the tower and amateur
antennas look like a much better ground than a typical small ground rod at the
service entrance. The largest portion of surge
flows through
house wiring to
station equipment,
and eventually out to the
low impedance antenna
system (A) and
station ground (B).

With
common lightning hits
on powerlines and powerline
surges, good grounds
installed at A and B
actually increase
current flowing
through house
wiring and
radio equipment when the power line gets
struck, or if the powerline has a
ground fault!

One path for lightning, common with above ground utilities and modest antenna
heights, is from powerlines to the house and tower grounds. It can also loop
from mains through telephone and cable equipment, or the cable and telephone can
also share bringing lightning energy into the house.

Another path for lightning, common with taller towers or underground
utilities, is from the tower through equipment to power mains, telephone, and/or
CATV lines. Water and gas lines can be included in the path.

Some of us disconnect
our antennas, and
consider everything
in the shack safe. If A is
disconnected and B
(the station ground
rod) remains connected,
the radio is still
in the lightning
path from D to B.
Disconnecting the
antenna doesn’t do
much, unless the
tower or antenna
takes a direct hit
or has induced
charges from a
nearby strike.
Disconnecting the
antenna is better than nothing, but not by very much. The only way to
eliminate more common lightning paths is to disconnect every path through equipment. Unplugging
the radio equipment
from the power line while disconnecting antennas helps, but there is
still significant
risk of lighting
flowing though
equipment on other paths from D
or C to A, or from D
or C to B unless all
external connections
are removed from
station equipment.

The best solution
is to bond point
C to point B with a much lower
impedance path than
any other path.
B
and C should always
be bonded together.
This is even spelled out in
the

National Electrical
Code. The
National Electrical
code says,”
Common
grounding is
important to
ensure an
electrically
continuous and
uninterrupted path
to properly
dissipate
lightning’s harmful
electricity.
Failure to make all
of the required
ground system
interconnections
is a common trouble
spot cited in
lightning protection
system inspections.“

Also, the desk equipment should be properly
connected in the hamshack. Proper radio room cable and power entrance RF grounding also works
well for lightning protection! Power lines feeding shack
equipment should be grounded to the same entrance point as the antennas. You can see
pictures of how I do this at the
end of
this article.

Proper building
and tower grounds,
and proper wiring methods, provide
virtually all
equipment lightning
protection. The
building entrance
ground must be
tied to the power
mains ground.
Any additional
work, such as improving grounds or adding lightning suppressors, will not mean
anything if entrance and mains bonding is incorrect (or does not exist)!

Second floor grounds offer a unique
(but similar) problem to installations in existing houses where the hamshack and
all cables, power wiring, and grounds cannot be at one single entrance point.

Click to
see typical ground layouts

Isolated Ground
Leads and Grounds (
Avoiding Ground
Loops)

Never isolate
RF cables on desk equipment with
feed line isolators.
Our equipment is
designed to operate with the
equipment tied
together with low
impedance cable
shields. The last thing we ever want are multiple cabinets with differing RF
potential on the operating desk. feed line isolators at a minimum belong outside,
at the cable entrance. Better yet, they belong at or near the antenna, or the
antenna system needs corrected.

The only
cables required to have
ground isolation are
audio
cables that connect between equipment with different chassis potentials, even
when the voltage potentials are relatively small. This is because shields are
not several skin depths thick at audio frequencies. Unless a shield is many skin
depths thick, common mode current, magnetic fields, or electric fields, will
easily move to the cable inside. 

While newer
equipment is 12-volt
operated, or has
three-wire grounded
plugs, older gear
often has internal
HV supplies and two
wire plugs. This
equipment must be
grounded to a good
earth path for
safety, otherwise
the case of the
equipment could rise
to more than the
highest voltage. For
example a blocking
capacitor failure in
an old radio, with
some antenna
configurations,
could elevate the s
chassis to full high
voltage. A line
bypass capacitor
could fail resulting
in 120 VAC on the
chassis, or a power
transformer could
short from primary
to a grounded
secondary winding,
adding the secondary
voltage to the power
line voltage and
applying it to the
chassis by pushing
against the power
line. Older
equipment also often
has power line
voltage, sometimes
un-fused, on
external relay
lines.

While more modern
gear is generally
safe, it is best to
always bond all gear
to a common heavy
buss on the
operating desk. This
buss should be
reliably bonded to a
good earth path.

Any claim you
should run isolated
grounds to the earth
from each piece of
gear is not only
false, it is also
dangerous. Such a
silly wiring scheme
actually encourages
ground loops, as
well as decreasing
electrical safety
for the operator.

Some amateur gear is
not grounded through
a three wire plug.
This equipment
requires an external
safety ground
connection to the
chassis. This means
some stations
actually require a
station ground buss.
This additional
ground at the desk
will never hurt, and
it will never bring
lightning in if
properly done. It
will only make
things better,
although it often is
not necessary.

More modern stations
sometimes do not require this
ground because all
of the gear has
three wire plugs or
is 12 volt operated.
If a station buss is
required, place it
at the desk. Every
piece of gear should
connect directly to
that buss as a
common point. That
common point should
run to the station
entrance panel on
one large flashing,
braid, or large
conductor wire. The
station entrance
panel ground must
ground all cable
grounds as they
enter, including
power mains and
telco grounds.
Everything has to be
at the same
potential entering
the room.
 

Do NOT
run a separate wire
from each piece of
gear to the ground
rod to avoid “ground
loops”. Do not use separate ground
rods to avoid ground
loops. Doing either
creates undesired
ground loops! This
is true at your
operating desk, at
the entrance, or at
the tower. Do NOT
use isolators on
coaxial lines at the
operating position.
That is not the
place for them, it
creates a harmful
situation!

My Station
Grounding

My ground system
works. My towers get
hit at least once in
every major
lightning storm, and
we have at least a
dozen severe
lightning storms a
year. I never
disconnect anything,
not even consumer
devices, and I have
never even lost a
sensitive computer modem or
delicate VCR to lightning.

Tower Grounds

The following is
typical of my tower
grounds:

Because this is
the point where most
lightning
current passes, the
grounds are wide
flashing high
temperature silver
soldered to the
ground rods. This
ground does not
reduce the chances
of a hit. It
prevents the cable
shields and control
wires leaving the
tower from being the
sole path for
lightning currents.
in other words, this
ground reduces
current on wires
leaving the tower
for the house in the
event the tower gets
a direct hit, or has
substantial charge
from a nearby
strike.

Some say we
have to cad weld to
have a good
connection. That
isn’t true. We
installed many
commercial towers
using silver solder,
and those ground
systems are still
good after 35 years.
The old green patina
flashing in the
picture was
installed in 1998.
The older 300-foot tower and
its grounding strap
has been removed,
but during its life
the silver soldering
survived what must
have been hundreds
of direct hits. This
is high temperature
hard silver solder,
not plumbing solder. 

#14 AWG radials
are also tightly
wrapped and soldered
with high
temperature silver
solder to a number 6
AWG solid buss wire.
That buss wire
follows the
perimeter of the
tower pad. I’ve
never had a #16 or
larger ground radial
fail from lighting
hits so long as
there are at least
ten of them to share
current.

I use copper pipe
for ground rods. To make the
connections to the
pipe, we use a step
bit and blocks of
wood to drill a
tight hole in the
copper flashing. We
force the flashing
down over the rod. We
fold it
slightly upwards to
cup the joint and fill the
resulting depression
with high
temperature silver
solder using a MAP
gas torch. You must
use high strength
high temperature
solder, not
traditional plumbing
solder.

All four corners
are grounded to the
tower legs. Most of
the real work in the
ground system is
done by the buried
radials, not the
pipes.

An interesting
point, I measured
the ground currents
in my old insulated
Rohn 45G 300-foot
tower. During an
approaching severe
thunderstorm, the
total corona current
was a few hundred
milliamperes
maximum. unless
there is a nearby or
a direct strike,
current is not that
high. Also, the
ground system does
not “bleed off” and
discharge clouds.
That is a myth.
There is no
discharge path to
the clouds other
than lightning.

Insulated-base Tower Protection

My insulated base Rohn 45G tower is protected by a shunt tower to ground (130
feet long), and spark gaps at legs.

Blackened area is from storm arcs.

These are commercial AM broadcast static drain chokes. Like static
dissipators, they do not prevent or reduce the number of hits. They do prevent
ungrounded towers from “trickle charging” to high voltages.

For amateur service on insulated towers or verticals, amplifier plate chokes
work OK. 100 µH is adequate inductance for a 160-meter 1/4
wavelength vertical.

Workshop
entrance and ground:

Entrance grounds
are critical.

This is the entrance
ground point of my
work shop. The
copper pipe has no
water, it is
actually a ground.
It is driven six
feet deep, and
connects to a buried
#8 buss wire running
around the outside
of the building.
Copper flashing ties
it to an entrance
bulkhead under the
rain hood. A number
six solid copper
wire ties the Telco
and alarm ground to
the feed line ground.
The power mains
(breaker box) is
also located inside
the building at this
same point, and it also
grounds to this
point.

Connection distance between cable entrance, Telco entrance, and antenna cable
entrance is virtually zero length.

House Ground

Receiving antenna,
transmitting
antenna,
and control cable
entrance at house:

Because the house was wired without the idea of a radio room, there isn’t any
way to have cables enter at the same point as the power lines and Telco lines
enter the house.

Ground conductors
and cable shields
entering the house
are grounded to wide
copper flashing. The
wide copper flashing
connects from my
station ground
inside the house to
the utility company
and circuit breaker
panel ground. The
perimeter of my
house has a #6 solid
copper ground wire
that bonds to the
water line, propane
tank, TV antenna
tower, satellite
cable, shack
entrance ground, and
telephone and
electric service
ground rod. The wide
flashing you see
also continues under
the house directly
to the power mains
entrance ground
about 30 feet away. 

This ensures
everything in the
house comes up at
nearly the same rate
during a lightning
strike. Large
lightning currents
do not flow through
the house wiring.

House station
internal common
point ground:

Transmitting cables
go to a single point
where an 8-position
relay cross-over
antenna switch
routes cables and
harmonic suppression
filters to various
radios. This switch
allows any tower’s
grouped feed line or
single antenna feed line to
be connected to any
radio. Receiver
cables are not wired
yet, but will go to
a common grounded
switching matrix.

Station power comes
from this point:

Every ground is
bonded to the common
point. That common
point is bonded to
the feed line
entrance ground with almost zero lead length. The
large relay
transfers a 25 kVA
generator on-line.

The power
distribution to my
desk follows:

The white outlet
distributes 120/240
volts continuous.
The smaller metal
outlet branches off
to feed a battery
backup supply for my
computer, VHF/UHF
radio, and scanner.

Radios and low power
equipment are
powered from a
master switched
outlet:

The following master outlet
strip feeds a
smaller strip for
very low power
devices:

Eventually these
cables will be
dressed up a little
more.

Protection is really
more about how
things are connected
than anything else.

For more grounding
look at my


contesting barn’s
entrance.

Also see my


Antenna Layout