Transmitters, like any other 50/60 Hz AC power operated equipment,
should be grounded for safety reasons.

This is done automatically via the AC power cable regardless of what
floor level the transmitter is located.

If a balanced feedline is used to the antenna then no other grounding
is needed.

If the antenna is an endfed wire then, for good RF radiating
efficiency, there should be a low impedance connection between the
TUNER and ground. The transmitter can still be left to its own
devices.

If the transmitter and tuner are in the same box then the low
impedance ground connection and the AC power ground are in parallel
with each other. This results in an even lower impedance RF ground
connection.

On whatever floor the transmitter + tuner is located, to obtain a low
impedance ground, connect everything in sight together via the
shortest reasonably possible wires, including hot and cold metal water
pipes, the domestic plumbing system, central heating system, not
forgetting the incoming water and gas mains.

The more the merrier! But only 2 or 3 distributed wires can be very
effective.

Running a copper strip down an outside wall to a set of shallow buried
radial wires in your back yard will be useful provided the length of
the copper strip is NOT 1/4-wavelength at your favourite operating
frequency. A single ground rod is wasted time, money and labour.

But, in general, if you live several floors up in a block of flats, a
centre-fed dipole of random length, fed via a 450-ohm ladder-line,
plus a tuner plus ckoke-balun, will be the more convenient and RF
power-efficient option.

Any objections from the experts and Guru's?
----
Reg, G4FGQ.

Any objections?

If there is no need for an RF ground, I think trying to
conjur one up is silly and just adds more problems.
IE: "virtual grounding"...Thats sillyness... :/

IE: ..
On whatever floor the transmitter + tuner is located, to obtain a low
impedance ground, connect everything in sight together via the
shortest reasonably possible wires, including hot and cold metal water
pipes, the domestic plumbing system, central heating system, not
forgetting the incoming water and gas mains.

Sounds like a good way to connect to a bunch of noise to me...
After all, ground is a noise source.
If the antenna is not fed directly from the shack, IE: end fed wire
from a shack tuner, I don't try to "rf" ground the shack. Being I
never feed directly from the shack, I never try to ground it.
I could be on the ground floor, or the 22nd, and I would not notice
any difference in operation. Also when mobile...Sure , I make sure
the ground under the antenna is very good. It's the rf ground. But..
I rarely bother grounding my rig itself. There is no real need.
Besides, it is grounded, when you consider the (-) power connection.
I know I'm a weirdo, but I think there are few cases where a ground
is required in radio operation. Overall, ground is either a bandaid,
or a
noise source, or a good place to lose useful rf due to excess
ground losses. The latter due to poor rf grounds under an antenna.
I think the farther one can stay away from grounds the better, overall.

I've never had much use for ground, except under vertical antennas, or
to safety ground high voltage gear like tube radios and amps.
MK

ORIGINAL MESSAGE:

Previously posted:

On whatever floor the transmitter + tuner is located, to obtain a low
impedance ground, connect everything in sight together via the
shortest reasonably possible wires, including hot and cold metal water
pipes, the domestic plumbing system, central heating system, not
forgetting the incoming water and gas mains.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Yep, those things radiate reeeeeely good, don'tcha know.

Busted any pileups lately?

73, Bill W6WRT

MK,
Unfortunately, grounds are sometimes necessary (neighbor, TVI/RFI),
even with dipoles/loops. Wish it weren't, I'm lazy...
'Doc

Unfortunately, grounds are sometimes necessary (neighbor, TVI/RFI),
even with dipoles/loops. Wish it weren't, I'm lazy...
'Doc

Hummmm...Maybe, but I'm having a hard time of thinking
of the uses of a ground to cure said problems... Most
of those problems would seem to be better cured using chokes,
etc. If the problem is fundamental overload to their gear, any
grounding on your end won't cure that.
MK

wrote:
Unfortunately, grounds are sometimes necessary (neighbor, TVI/RFI),
even with dipoles/loops. Wish it weren't, I'm lazy...
'Doc


Hummmm...Maybe, but I'm having a hard time of thinking
of the uses of a ground to cure said problems... Most
of those problems would seem to be better cured using chokes,
etc. If the problem is fundamental overload to their gear, any
grounding on your end won't cure that.
MK

If you have an imbalance current trying to find its way to ground, it'll
take the path of least resistance (technically, impedance). If that path
is the mains wiring, you have a lot of potential for RFI. If you can
convince some of that current to go elsewhere by "grounding" your
station, you're likely to cut down the RFI. But a better solution is to
get those feedline currents balanced so you won't have any imbalance or
"ground" current to deal with in the first place. It brings the added
benefit of putting the power into your antenna to be radiated rather
than being radiated from the conductors carrying the imbalance current.

Roy Lewallen, W7EL

Radiation from the feedline is usually the least of one's problems.

99 % of RFI is due to radiation from the very nearby antenna.

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

Roy Lewallen wrote:
wrote:
Unfortunately, grounds are sometimes necessary (neighbor, TVI/RFI),
even with dipoles/loops. Wish it weren't, I'm lazy...
'Doc
Hummmm...Maybe, but I'm having a hard time of thinking
of the uses of a ground to cure said problems... Most
of those problems would seem to be better cured using chokes,
etc. If the problem is fundamental overload to their gear, any
grounding on your end won't cure that. MK

If you have an imbalance current trying to find its way to ground,
it'll take the path of least resistance (technically, impedance). If
that path is the mains wiring, you have a lot of potential for RFI. If
you can convince some of that current to go elsewhere by "grounding"
your station, you're likely to cut down the RFI. But a better solution
is to get those feedline currents balanced so you won't have any
imbalance or "ground" current to deal with in the first place. It
brings the added benefit of putting the power into your antenna to be
radiated rather than being radiated from the conductors carrying the
imbalance current.

Sometimes the improvements to the antenna and feedline are not enough to
prevent interference. Also, RF grounding may be ineffective because it's
impedance is too high to successfully shunt the ground current away from
the mains wiring.

However, there is also a third option: use a series RF choke in the
station mains feed. This can have two beneficial effects. It keeps the
ground currents out of the mains where they can cause interference, and
it can also reduce the incoming common-mode current on the feedline.

A suitable mains choke for the whole station can be made by winding
*all* of the mains conductors (live, neutral and safety ground) on a
stack of ferrite rings. It's necessary to choke all the mains wires
because they are capacitively coupled together at RF. The choke is a
high impedance at RF, but the safety ground wire is continuous through
the choke. Alternatively you could thread all the wires through a string
of large ferrite beads. Of course it's no coincidence that these mains
chokes look a lot like the chokes you'd use on a feedline.

An alternative is to use a commercial three-wire mains filter, which has
an RF choke in the ground conductor, as well as the normal pi-filter in
the power conductors. (I wouldn't recommend a homebrew mains filter. The
safety and code compliance issues are better left to full-time
specialists.)

Another essential is to organize the mains wiring of the whole station
so that *all* the mains feeds and mains ground connections pass through
the RF choke. (This goes along with the established safety
recommendation to have one Big Red Switch supplying mains to the whole
shack.) If there is a sneak path to ground that doesn't go through the
station mains choke, then of course the RF current will take that easier
path and the choke will be ineffective.

A clip-on RF current meter is an excellent trouble-shooting tool. There
are constructional details on my 'In Practice' pages, and MFJ sell two
different ready-made models.

When you have installed a station mains choke and eliminated all sneak
ground paths, the RF current meter will show you two things:

1. Without an RF ground, the incoming common-mode currents should be
significantly lower than before. In simple terms, common-mode feedline
currents cannot enter the shack if you have choked off their exit path
to ground.

If you try to look at the situation in more technical detail, there are
more unknowns (such as distributed capacitance to ground) than you can
accurately identify. That's why RFI is so hard to predict and generalize
about. Therefore the best approach is always to *measure* the RF
currents on all entering and exiting conductors, before and after each
modification you try.

2. An RF ground connection may make the common-mode currents *worse* by
providing a path through the station. If that is the case, then don't
use an RF ground - it isn't compulsory to have one. (You still have to
think about lightning protection, but that most certainly does *not*
involve routeing the lightning currents to ground through your shack!)

There are three good articles on RF grounding in the public area of the
ARRL website:
http://www.arrl.org/tis/info/grounding.html



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

If you have an imbalance current trying to find its way to ground,
it'll
take the path of least resistance (technically, impedance). If that
path
is the mains wiring, you have a lot of potential for RFI. If you can
convince some of that current to go elsewhere by "grounding" your
station, you're likely to cut down the RFI. But a better solution is to
get those feedline currents balanced so you won't have any imbalance or
"ground" current to deal with in the first place. It brings the added
benefit of putting the power into your antenna to be radiated rather
than being radiated from the conductors carrying the imbalance current.


Exactly. This is why I call the "grounding" method a bandaid.
I think the 2nd solution is the best route to go. And if you use
the 2nd solution, the length of the line, and the location or height
above ground will not matter. And no worrying about getting a
good rf ground, which is hard to do in many remote locations of
a building.
MK

ORIGINAL MESSAGE:

On Mon, 02 Jan 2006 23:19:15 -0800, Roy Lewallen
wrote:

But a better solution is to
get those feedline currents balanced so you won't have any imbalance or
"ground" current to deal with in the first place.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Not only that, but whenever the neighbor plugs in a different
appliance, uses an extension cord or otherwise rearranges his AC
mains, your problem may be right back.

73, Bill W6WRT