Why ground the transmitter?
 

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.

Why ground the transmitter?
 

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

Why ground the transmitter?
 

ORIGINAL MESSAGE:

On Mon, 2 Jan 2006 17:09:08 +0000 (UTC), "Reg Edwards"
wrote:

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.

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

End fed wires should only be used for transmitting when people are
bleeding and the phone is out.

73, Bill W6WRT

Why ground the transmitter?
 

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

Why ground the transmitter?
 

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

Why ground the transmitter?
 

Why is that? I use them all the time with excellent results.
Mike


Bill Turner wrote:
ORIGINAL MESSAGE:
End fed wires should only be used for transmitting when people are
bleeding and the phone is out.

73, Bill W6WRT

Why ground the transmitter?
 

ORIGINAL MESSAGE:

On Tue, 03 Jan 2006 00:45:45 GMT, Mike
wrote:

Why is that? I use them all the time with excellent results.
Mike


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

Your results are "excellent' because you've never used anything
better. Put up a modest yagi and prepare to be amazed. Even a good
dipole will beat a longwire worked against ground.

73, Bill W6WRT

Why ground the transmitter?
 

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

Why ground the transmitter?
 

Why ground the transmitter?
 

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

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

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

Why ground the transmitter?
 

Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

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


That's rubbish - have you ever *measured* the RF currents in your
station wiring?

....no, I thought not.



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

Why ground the transmitter?
 

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

Why ground the transmitter?
 

That's an interesting statistic. How did you arrive at it?

Roy Lewallen, W7EL

Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

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

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

Why ground the transmitter?
 

"Ian White GM3SEK" wrote
Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

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


That's rubbish - have you ever *measured* the RF currents in your
station wiring?

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

No, but I HAVE measured RF current in the antenna - from where most
RFI originates.

Have you ever run 400 watts from an 80 meter 1/2-wave dipole a few
feet above your roof and not far from the TV aerial?
----
Reg.

Why ground the transmitter?
 

Roy!

Just a legitimate crude guess - perhaps biassed a little in the
opposite direction to the normal excessive bias.

If I remember correctly, you, your very good self, used Eznec to
demonstrate that even under the most adverse worst-case conditions you
could think of, power radiated from the feedline is only a fraction of
that radiated from the antenna.

.. . . . . and the equipment being interfered with is in the
near-field of the antenna just as it is in the near-field of the
feedline. That, for most people, includes your next-door neighbors.
Especially if your next-door neighbors happen to be within the antenna
beam.
----
Reg.

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

"Roy Lewallen" wrote
That's an interesting statistic. How did you arrive at it?

Roy Lewallen, W7EL

Reg Edwards wrote:
Radiation from the feedline is usually the least of one's
problems.

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

Why ground the transmitter?
 

Reg Edwards wrote:

"Ian White GM3SEK" wrote
Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

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


That's rubbish - have you ever *measured* the RF currents in your
station wiring?

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

No, but I HAVE measured RF current in the antenna - from where most
RFI originates.

Can't you see the circularity of your own 'logic'? If you haven't
measured common-mode RF current in the feedline as well, you don't
actually have a clue where the interference is originating. All you have
is an unsubstantiated opinion.


Have you ever run 400 watts from an 80 meter 1/2-wave dipole a few
feet above your roof and not far from the TV aerial?

I'm not disputing that RFI very often originates from the antenna - of
course it does (and the question you pose is a set-up, designed to make
*sure* it does).

What I object to is your sweeping generalization that "99 % of RFI is
due to radiation from the very nearby antenna." When absolute nonsense
is delivered with absolute confidence, some unfortunate beginner might
actually believe it.

However, since you asked...

In a typical small British back garden, I have been forced to do
something very similar to what you describe. Sure enough, it caused RFI,
but the interference was *not* due to my antenna! It was entirely
mains-borne, and only to the two neighbours (not the closest) who were
connected to the same phase as ourselves. The cause of the interference
was that a substantial fraction of my RF ground current was going into
the mains ground. Once I'd cleaned up my act and stopped injecting RF
current into the mains, the interference stopped too.

The high field strength from my antenna wasn't a problem at all, and the
neighbours continued to watch their TVs until I took the antenna down.

That's how it was in that one particular case.... but unlike you, I'm
not claiming it represents 99% of anything.

With RFI, the only safe generalization is to keep your mind open to
*all* possibilities.


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

Why ground the transmitter?
 

Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

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

In some cases, that nearby antenna is a counterpoise
laid across the floor which some people consider to
be a "ground" of sorts. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Why ground the transmitter?
 

Reg Edwards wrote:
Radiation from the feedline is usually the least of one's problems.

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

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


REALLY??

I thought most RFI issues, in today's world, are related to lack of
selectivity in the device experiencing the interference. RFI is
generally a susceptibility in the interefered with device. Read ALL the
information provided and you should find a manufacturer's disclaimer.

If the transmitted signal is 'clean' [meets applicable standards] then
the cause of RFI is SUSCEPTIBILITY in devices designed for MAXIMUM profit.

I'm not responsible for susceptibility issues. A neighbor complained
that my station was coming through his computer speakers. I invited him
to my station and turned on my computer and speakers. At 1 KW output
there was/is no RFI in my speakers !!! [My computer is co-located with
my station]. I suggested that he contact the manufacturer of the
speakers and obtain information to reduce susceptibility. I showed him
how I solved the susceptibility issue for my computer. The
responsibility is now his.

Why ground the transmitter?
 

On Tue, 3 Jan 2006 14:44:01 +0000, Ian White GM3SEK
wrote:

Can't you see the circularity of your own 'logic'? If you haven't
measured common-mode RF current in the feedline as well, you don't
actually have a clue where the interference is originating. All you have
is an unsubstantiated opinion.

Ian, Ian you should know by now you're dealing with the "Prince of
Factoids".

Danny, K6MHE




email: k6mheatarrldotnet
http://www.k6mhe.com/

Why ground the transmitter?
 

On Mon, 02 Jan 2006 20:30:21 -0800, Bill Turner
wrote:

Even a good
dipole will beat a longwire worked against ground.


Not always!

Danny, K6MHE



email: k6mheatarrldotnet
http://www.k6mhe.com/

Why ground the transmitter?
 

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

Why ground the transmitter?
 

MK,
The 'problem' wasn't completely on my end (neighbor's defective
devices), but a good grounding did help cure the a RFI. Is grounding
a 'sure thing' as a cure? Nope, but it certainly doesn't hurt if it's
at all possible, which isn't always a 'sure thing'.
Also used to use a fence around the place as a ground. Very BAD idea
since the fence was connected to the neighbor's fence too. Just 'took'
the RF closer to the neighbor, probably a 'sort' of direct connection to
his 'stuff'. Always a 'bad' idea? No, but something to think about.
'Doc

Why ground the transmitter?
 

Reg, it would really be nice if you could come up with some new topics
to keep you entertained on those dull evenings. You brought that one up
just four months ago. Maybe you can keep a list of your favorites,
noting when you used each one the last time, and giving us a little
longer break between repetitions.

Reg Edwards wrote:
Roy!

Just a legitimate crude guess - perhaps biassed a little in the
opposite direction to the normal excessive bias.

If I remember correctly, you, your very good self, used Eznec to
demonstrate that even under the most adverse worst-case conditions you
could think of, power radiated from the feedline is only a fraction of
that radiated from the antenna.

Sorry, you don't remember correctly. I said on quite a number of
occasions (and you once even agreed) that you can't assign radiated
powers from different parts of an antenna system. It was actually kind
of sad -- you kept loudly demanding that I provide fractions of power
from the feedline and antenna, ignoring my statements that it couldn't
be apportioned that way, and some time later you said out of the blue
that it couldn't. And then you wrote a program that does just that. At
the end of this posting is a summary of your contradictory statements
which I originally posted here on Sept. 1.

I did find with EZNEC that the current on a feedline could be very much
larger than your program predicts.

. . . . . and the equipment being interfered with is in the
near-field of the antenna just as it is in the near-field of the
feedline. That, for most people, includes your next-door neighbors.
Especially if your next-door neighbors happen to be within the antenna
beam.

Depends on the orientation of your antenna and the size of your lot. My
antennas are some distance from the house, but the feedlines come right
inside.

----- My posting on this group on 9-1-2005 -----

If anyone besides me is having trouble keeping track of what Reg is
trying to say, maybe the following recent quotes will help. That is,
they'll help you understand why you're having trouble keeping track.

For what it's worth, I agree with the first quotation of 8/31. But
apparently Reg doesn't, even though he said it.

Roy Lewallen, W7EL

8/30:

Perhaps somebody might be prepared to state the power actually
radiated from feedlines in watts. At least it may create the
impression you know what you are talking about.

8/30:

Roy, do everybody a favour, by stating, numerically, how much power is
radiated from feedlines. Then somebody might have some confidence in
what you are bafflegabbing about.

8/31:

Any current which finds its way on to (3), which ought to flow in the
antenna, will result in the coax participating in the radiation
pattern of the whole antenna structure.

BUT IT IS A SILLY QUESTION TO ASK HOW MANY WATTS ARE RADIATED FROM THE
FEEDLINE.

OR, CONVERSELY, HOW MANY MICROWATTS ARE PICKED UP BY THE FEEDLINE ON
RECEIVE.

The feedline cannot be treated in isolation as if it behaves
independently of the antenna. For starters, the radiation resistances
of the feedline and antenna do not add arithmetically. They interact
with each other.

8/31:

If you erect a 10 meter 1/2-wave dipole and center-feed it with a 50
feet length of coax, and then transmit on 1.9 MHz, 99.9 percent of
available power will be radiated from the feedline and only 0.1
percent from the antenna itself.

http://www.smeter.net/feeding/feedpowr.php:

Centre-Fed Dipole - Radiation from Coaxial Feedline
Author: R.J.Edwards G4FGQ © 25th March 2003

Program Notes
.. . .
With no loss in accuracy, to simplify the model, the transmitter is
located at the dipole centre and the coaxial line is replaced by a
single conductor of the same diameter as the coaxial braid. There are 3
radiating elements. Radiation resistance, input impedance, and input
current of each element is calculated. Finally, the percent of total
power radiated by each of the three elements is calculated.

---------------------

Roy Lewallen, W7EL

Why ground the transmitter?
 

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