I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too? (I know the radio always needs a DC
ground, of course). How about if the dipole is being used as a
non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER
LINE--DIPOLE) -- would this affect the need for an RF ground on the rig
for operation in the dipole's non-resonant bands? Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

Thanks!

Bill

"billcalley" wrote in message
oups.com...
I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too? (I know the radio always needs a DC
ground, of course). How about if the dipole is being used as a
non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER
LINE--DIPOLE) -- would this affect the need for an RF ground on the rig
for operation in the dipole's non-resonant bands? Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

With ladder line it is best to use a balun between the antenna tuner and the
transmission line. An RF ground on the rig is then not required (you won't
have RF voltages on the rig's chassis).

The thing about an RF ground is that due to the length of the ground
circuit, the rig is often not grounded anyway.

billcalley wrote:
I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too?

If your feedline is balanced, that is it has equal and opposite currents
on the two conductors, then there's no current left over to flow to or
from ground and no need for an RF ground connection. All the current
from one conductor goes back on the other. Feedlines can be balanced
even if they're coax and/or the antenna is unsymmetrical; they can be
unbalanced even if the antenna and feedline are symmetrical.

If the feedline isn't balanced, the difference current (that is, the
difference between the currents on the two feedline conductors) will
find its way to ground however it can. This often creates undesirable
effects. But if you can't avoid it, it's better to provide a low
impedance path for the ground current if possible. And that can
sometimes be difficult to do.

(I know the radio always needs a DC
ground, of course).

No, it doesn't. It needs an AC safety ground if connected to the mains,
and a lightning ground if that's a possible hazard. But DC isn't important.

How about if the dipole is being used as a
non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER
LINE--DIPOLE) -- would this affect the need for an RF ground on the rig
for operation in the dipole's non-resonant bands? Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

The trick is to get the feedline balanced on all bands. That requires
either a truly balanced tuner, or a combination of a good balun and
impedances on all bands at the balun which the balun can handle.

Roy Lewallen, W7EL

ORIGINAL MESSAGE:

On 1 Jan 2006 12:47:43 -0800, "billcalley"
wrote:

Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

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

Any antenna which requires a connection to ground should be shown the
trash can immediately. Ground (earth) is a lousy conductor and does
nothing to help your signal. RF belongs up in the air, not down in the
dirt.

If you find that connecting a ground wire actually improves your
signal, you have a SERIOUS problem in your antenna.

73, Bill W6WRT

Charles Schuler wrote:


"billcalley" wrote in message
oups.com...
I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too? (I know the radio always needs a DC
ground, of course). How about if the dipole is being used as a
non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER
LINE--DIPOLE) -- would this affect the need for an RF ground on the rig
for operation in the dipole's non-resonant bands? Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

With ladder line it is best to use a balun between the antenna tuner and
the
transmission line. An RF ground on the rig is then not required (you
won't have RF voltages on the rig's chassis).

The thing about an RF ground is that due to the length of the ground
circuit, the rig is often not grounded anyway.




Most modern shacks have to long distance between the rig and ground. It's
not equal to an ungrounded rig but you might experience hf in your shack.

This is best solved by a short ground cable to a proper ground rod.

The next best thing is to buy or build an artificial ground. It's very
simple and can be made to cover all ham bands easily and will always give
you a perfect length of the earth cable... By cheating of course - but it
works!


Cheers

M0DFI

billcalley wrote:

I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too? (I know the radio always needs a DC
ground, of course). How about if the dipole is being used as a
non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER
LINE--DIPOLE) -- would this affect the need for an RF ground on the rig
for operation in the dipole's non-resonant bands? Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

Thanks!

Bill



Get a virtual earth! They are easy to build for all ham bands!

It's basically a phasing unit for the earth connection which can null the
voltage on the earth at the RF Rig!


Cheers

M0DFI

ORIGINAL MESSAGE:

On Mon, 02 Jan 2006 00:12:21 +0000, Dan Andersson
wrote:

This is best solved by a short ground cable to a proper ground rod.


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

No it isn't.

It's best solved by keeping the RF out of the shack in the first
place. Even if you could "ground" your RF, why would you want to run
your RF through dirt? Is dirt a good antenna?

73, Bill W6WRT

"billcalley" wrote in news:1136148463.132269.164130
@g49g2000cwa.googlegroups.com:

I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too? (I know the radio always needs a DC
ground, of course). How about if the dipole is being used as a
non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER
LINE--DIPOLE) -- would this affect the need for an RF ground on the rig
for operation in the dipole's non-resonant bands? Or is no RF ground
_at all_ required with a dipole; unlike when using random wires or
verticals, and other such un-balanced antennas?

If the antenna is TRULY balanced and the feedline dressed well away from it
at right angles you should have no common-mode currents on the feedline.
That's the ideal case and in that ideal case you need no RF ground at the
radio. The ideal case, however, rarely ever exists in practice.

And end-fed wires can be a whole different ball game. I had to use a 16
foot counterpoise once to "ground" a rig in a 2nd story location when I
end-fed a very long wire with it.



--
Dave Oldridge+
ICQ 1800667

Thanks Guys -- I really appreciate the clarifications on grounding! It
sometimes gets a bit confusing for me.

Best Regards,

Bill

Dave Oldridge wrote:

If the antenna is TRULY balanced and the feedline dressed well away from it
at right angles you should have no common-mode currents on the feedline.
. . .

That only prevents one of the two ways common mode current can be
created, by coupling. It can also be created by conduction. A common
example is a coax-fed dipole, where the current in the outer feedline
conductor splits between the antenna conductor and the outside of the
coax. An equivalent problem can occur when a dipole is fed with
symmetrical line such as ladder line, and one conductor of the line is
connected to the rig's chassis at the rig end. The current on the inside
of the chassis is equal to the current from the "hot" conductor, and
this splits between the transmission line conductor and the outside of
the chassis. A detailed explanation of conducted common mode current can
be found at http://eznec.com/Amateur/Articles/Baluns.pdf.

Roy Lewallen, W7EL