Which one of the the two is more efficient as a radiator & why?

1/2 wave vertical fed in the center with coax or one vertical 1/4 wave
with four 1/4 wave radials also fed in the center with coax?

"N3" wrote in news:1156112798.027258.152330
@m73g2000cwd.googlegroups.com:

Which one of the the two is more efficient as a radiator & why?

1/2 wave vertical fed in the center with coax or one vertical 1/4 wave
with four 1/4 wave radials also fed in the center with coax?




The vertical dipole has more horizontal gain than the groundplane. I
believe its about 1dB improvement.



Ed K7AAT

On 20 Aug 2006 23:54:28 GMT, Ed wrote:
"N3" wrote:

Which one of the the two is more efficient as a radiator & why?

1/2 wave vertical fed in the center with coax or one vertical 1/4 wave
with four 1/4 wave radials also fed in the center with coax?

The vertical dipole has more horizontal gain than the groundplane.
I believe its about 1dB improvement.

Actually, *neither* one has any "gain". :-)

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: http//jonz.net/ng.htm

The vertical dipole has more horizontal gain than the groundplane.
I believe its about 1dB improvement.


Actually, *neither* one has any "gain". :-)



Its all a matter of reference. I was thinking in terms of dBi.... a
vertical has 3dBi gain, a ground plane, 2 dBi.


Ed K7AAT

On 21 Aug 2006 17:50:21 GMT, Ed
wrote:
Its all a matter of reference. I was thinking in terms of dBi.... a
vertical has 3dBi gain, a ground plane, 2 dBi.

Hi Ed,

The missing "reference" is that the vertical is planted into earth
(because both antennas are vertical, this missing "reference" should
be very explicitly stated). However, in the context of 2M FM, an
antenna planted into the ground, unless that ground happens to be the
peak of a mountain, is rather a very poor option for 1dB "gain."

73's
Richard Clark, KB7QHC

The missing "reference" is that the vertical is planted into earth
(because both antennas are vertical, this missing "reference" should
be very explicitly stated). However, in the context of 2M FM, an
antenna planted into the ground, unless that ground happens to be the
peak of a mountain, is rather a very poor option for 1dB "gain."



I've lost you here, on the "planted into earth" part. The original
poster was asking about 2M vertical vs. groundplane antenna. I would
assume for 2M that either antenna would be up in the air..... ???



Ed K7AAT

On 21 Aug 2006 17:50:21 GMT, Ed
Its all a matter of reference. I was thinking in terms of dBi.... a
vertical has 3dBi gain, a ground plane, 2 dBi.

Here is a ground plane with a free-space gain greater than 2.9 dBi and
an SWR less than 1.2 at its design frequency (as given by NEC2):

CM Groundplane antenna for MURS (151.8 Mhz)
CE
GW 1 19 0 0 0 0 0 0.444243 0.000813863
GW 2 21 0 0 0 0 0.163546 -0.4506 0.000813863
GW 3 21 0 0 0 0 -0.163546 -0.4506 0.000813863
GW 4 21 0 0 0 -0.163546 0 -0.4506 0.000813863
GW 5 21 0 0 0 0.163546 0 -0.4506 0.000813863
GE 0
FR 0 31 0 0 145 0.33
EX 0 1 1 0 1
RP 0 31 73 1001 0, 0, 3, 5, 10000, 0
EN


It uses 14 AWG wire and consists of a 17-1/2 inch vertical, and 4
18-7/8 inch radials symmetrically placed at about 20 degrees with
respect to the vertical axis:

|
|
| A A = 17-1/2 in
| B = 18-7/8 in
| T = 2*19.95 degrees
/ \ C = 12-7/8 in
/ T \ B
/ \ (only 2 radials shown)
/ \
-- C --

--John

You should always run an average gain test when you have an unusually
high or low field strength. Using EZNEC, the average gain shows as
1.227, or 0.89 dB, and this same average gain should be reported by
NEC-2. That means that the actual gain is 0.89 dB less than what NEC-2
is reporting, or just about 2.0 dBi. If you don't understand what this
test is, consult the NEC-2 manual. EZNEC users will find it indexed in
the EZNEC manual.

I suggest you also do an average gain check on your 3 dBi vertical.

Roy Lewallen, W7EL

John E. Davis wrote:
On 21 Aug 2006 17:50:21 GMT, Ed
Its all a matter of reference. I was thinking in terms of dBi.... a
vertical has 3dBi gain, a ground plane, 2 dBi.

Here is a ground plane with a free-space gain greater than 2.9 dBi and
an SWR less than 1.2 at its design frequency (as given by NEC2):

CM Groundplane antenna for MURS (151.8 Mhz)
CE
GW 1 19 0 0 0 0 0 0.444243 0.000813863
GW 2 21 0 0 0 0 0.163546 -0.4506 0.000813863
GW 3 21 0 0 0 0 -0.163546 -0.4506 0.000813863
GW 4 21 0 0 0 -0.163546 0 -0.4506 0.000813863
GW 5 21 0 0 0 0.163546 0 -0.4506 0.000813863
GE 0
FR 0 31 0 0 145 0.33
EX 0 1 1 0 1
RP 0 31 73 1001 0, 0, 3, 5, 10000, 0
EN


It uses 14 AWG wire and consists of a 17-1/2 inch vertical, and 4
18-7/8 inch radials symmetrically placed at about 20 degrees with
respect to the vertical axis:

|
|
| A A = 17-1/2 in
| B = 18-7/8 in
| T = 2*19.95 degrees
/ \ C = 12-7/8 in
/ T \ B
/ \ (only 2 radials shown)
/ \
-- C --

--John

Let's not confuse "efficiency" with "gain". Efficiency asks, "Of the power
that is incident at the feed point of the antenna, how much of that power is
radiated into free space and how much is wasted as reflected or consumed in
losses (matching or the elements themselves)?"

Gain asks, "For a receiver far distant (in terms of wavelengths) from the
antenna, which antenna produces a higher signal strength?"

In the latter, which is what I presume you meant, we have to have a
reference of some sort ... we have a fictitious impossible antenna called
"isotropic", which says that all power is radiated from a point source that
is infinitely small and infinitely efficient ... that is, all the power
incident on the point is radiated equally in all spherical directions ... a
radiating molecular seed at the center of an orange the size of Yankee
stadium.

If you measure a perfect dipole with respect to this isotropic source, you
find a "gain" perpendicular to the dipole elements of 2.14 dB. Where did
this "gain" come from, since power can not be created by a passive antenna?
If you look at the radiation pattern of a dipole, this apparent increase in
power was caused by a deep hole in the pattern off the ends of the dipole.
THe dipole, in essence, squeezed the top and the bottom to let the sides
bulge out. Think of a donut dropped over the elements and sitting at the
feed point of the dipole.

For the ground plane, think of that same donut cut in half through the fat
part of the donut. Now since our "power" is really the volume of the donut,
if you cut it in half, you are going to have to start out with a fatter
donut if you are going to wind up with the same volume. Now drop that fat
donut over the radiating element and let it come to rest on the center of
the ground plane. The dipole radiated its energy so that half of it was
"up" and half of it was "down". If "down" into the ground isn't what you
wanted, then the ground plane, which radiates all of its energy "up" at some
angle to the horizon, has more gain. By a clever bending of the ground
plane wires down at some angle to the horizon, you can move that donut
pattern down to where it is nearly horizontal. Thus, for a person at some
far distance, a properly constructed ground plane will appear to have a
stronger signal relative to a dipole.

Jim



"N3" wrote in message
oups.com...
Which one of the the two is more efficient as a radiator & why?

1/2 wave vertical fed in the center with coax or one vertical 1/4 wave
with four 1/4 wave radials also fed in the center with coax?

"N3" wrote in message
oups.com...
Which one of the the two is more efficient as a radiator & why?

1/2 wave vertical fed in the center with coax or one vertical 1/4
wave
with four 1/4 wave radials also fed in the center with coax?

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

They are both equally efficient. There's no reason why they should be
otherwise.

Hint : Try not to confuse efficiency with gain.