I have seen some with 4 elements, some with 5. Also is the spacing
between them important?

On 10 Jan 2005 08:48:37 -0800, wrote:

I have seen some with 4 elements, some with 5. Also is the spacing
between them important?

The ¼-wave groundplane was developed by George Brown 1938. Here's a
partial quote from his book:

"... In our initial experiments we found that only two horizontal rods
(ground rods) functioned as well as four. Many people from the
Broadcast Sales organization came by to view our tests and they always
expressed doubts as to the ability to radiate uniformly when only two
ground rods were used. To quiet them, we used four ground rods for a
while, thus stilling the criticism. When the antenna became really
popular, we did not dare confess to our ruse."

There you have it from the inventor of the antenna.

73
Danny, K6MHE

"Dan Richardson" wrote in message
...
On 10 Jan 2005 08:48:37 -0800, wrote:

I have seen some with 4 elements, some with 5. Also is the spacing
between them important?

The ¼-wave groundplane was developed by George Brown 1938. Here's a
partial quote from his book:

[deleted]

Interesting... although while I'd certainly believe that, as far as Georbe
Brown could tell in 1938 two radials performed just as well as four radials,
I'd imagine that there is a measurable and simulatable different between the
two systems!

(Hmm... I know... how about... three! ground radials? :-) )

---Joel

Interesting... although while I'd certainly believe that, as far as
Georbe Brown could tell in 1938 two radials performed just as well as
four radials, I'd imagine that there is a measurable and simulatable
different between the two systems!

(Hmm... I know... how about... three! ground radials? :-) )


Actually, for decades, I have built and used 3 radial ground plane
antennas for 2M and for 440. I simply used brass welding rods and SO-
239 connectors to construct them. The reason I used 3 radials.... I too
was under the misconception that 4 were best, but I had a slight
difficulty adding the 4th radials to my SO-239s so I stuck with three.
Incidently, I found the best 50 ohm match was made when I bent the
radials down about 45 degrees. They worked extremely well when properly
tuned and stood up to some pretty heavy weather, too.



Ed

Joel Kolstadt wrote:
"Hmm...how about...three! ground radials?"

Three radials should be fine where they are elevated to such height that
they capture all the electric lines of force from the vertical
radiator.Radials are balanced and their currents travel in offsetting
directions. The radial system does not radiate itself because of its
offsetting balances. Elevated radials must shield the earth from induced
current. This requires few radials when the radials are far above the
earth, but where the radials are near to the earth, many radials are
needed to capture all the electric lines and shield the earth from lossy
currents.

The number of radials and their effect on pattern and efficiency of
radiation from a vertical antenna is well addressed by ON4UN in
"Low-Band DXing". This is found in Chapter 9 of my 2nd edition. Choose
the efficiency and elevation angle you are willing to accept ftom the
graphs and tables presented.

Best regards, Richard Harrison, KB5WZI

You only need two to result in field cancellation
to prevent radiation. However, that is only the
case in free space. Any near objects or objects
in electrical contact may distort
the field from one of the elements differently
from the other, so resulting in less-than-perfect
cancellation, especially in the case of ground radials.

"Dan Richardson" wrote in message
...
On 10 Jan 2005 08:48:37 -0800, wrote:
I have seen some with 4 elements, some with 5. Also is the spacing
between them important?
The ¼-wave groundplane was developed by George Brown 1938. Here's a
partial quote from his book:
"... In our initial experiments we found that only two horizontal rods
(ground rods) functioned as well as four. Many people from the
Broadcast Sales organization came by to view our tests and they always
expressed doubts as to the ability to radiate uniformly when only two
ground rods were used. To quiet them, we used four ground rods for a
while, thus stilling the criticism. When the antenna became really
popular, we did not dare confess to our ruse."
There you have it from the inventor of the antenna.

PS. The same effect occurs in the so-called "capacity hat".
The waves rushing out and returning in both directions result
in field cancellation and no radiation from the hat in the
ideal case. "Capacity Hat"? - Because the delayed returning
waves in recombination at the top of the radiator behave
as though they have picked up a capacitive phase change.

"Airy R.Bean" wrote in message
...
You only need two to result in field cancellation
to prevent radiation. However, that is only the
case in free space. Any near objects or objects
in electrical contact may distort
the field from one of the elements differently
from the other, so resulting in less-than-perfect
cancellation, especially in the case of ground radials.

"Dan Richardson" wrote in message
...
On 10 Jan 2005 08:48:37 -0800, wrote:
I have seen some with 4 elements, some with 5. Also is the spacing
between them important?
The ¼-wave groundplane was developed by George Brown 1938. Here's a
partial quote from his book:
"... In our initial experiments we found that only two horizontal rods
(ground rods) functioned as well as four. Many people from the
Broadcast Sales organization came by to view our tests and they always
expressed doubts as to the ability to radiate uniformly when only two
ground rods were used. To quiet them, we used four ground rods for a
while, thus stilling the criticism. When the antenna became really
popular, we did not dare confess to our ruse."
There you have it from the inventor of the antenna.

In message .com,
writes
I have seen some with 4 elements, some with 5. Also is the spacing
between them important?

A ground plane is an attempt to simulate the earth, with better
conduction, so the more radials the better.

Mike
--
M.J.Powell

M. J. Powell wrote:
In message .com,
writes
I have seen some with 4 elements, some with 5. Also is the spacing
between them important?

A ground plane is an attempt to simulate the earth, with better
conduction, so the more radials the better.

Mike
--
M.J.Powell


Is that a joke?

On another note, why are some of the radials bent to a 45 degree angle
and some are not?

wrote in message
oups.com...
Is that a joke?

No, in most implementations, ground radials are very much attempting to
simulate a solid, perfectly conducting plane under the antenna. Given
enough of them, they do a reasonably good job.

On another note, why are some of the radials bent to a 45 degree angle
and some are not?

As you go to few and fewer radials, the 'pull' of the 'simulated' ground
becomes 'weaker' in a sense and the radiation pattern of an antenna with
horizontal radials tends to have its maximum at an angle significantly above
the horizontal plane. By angling the radials downward, the radiation
pattern is pulled back downward and the maximum radiation is again more or
less horizontal.

(If you don't like this 'maybe intuitive to me and not at all to you'
explanation, you can simulate an antenna with radials in, e.g., ezNEC and
see what the actual results are...)

---Joel Kolstad