Two Meter FM Antenna Question
 

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?

Two Meter FM Antenna Question
 

"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

Two Meter FM Antenna Question
 

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

Two Meter FM Antenna Question
 

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

Two Meter FM Antenna Question
 

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

Two Meter FM Antenna Question
 

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

Two Meter FM Antenna Question
 

On 21 Aug 2006 18:35:41 GMT, Ed
wrote:

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..... ???

Hi Ed,

In that case, the gains are identical. A vertical "planted into the
earth" exhibits a higher gain (given many other considerations) than
an elevated vertical - be that elevated vertical be a dipole or a
ground plane design (which is simply another dipole, albeit rather
more elaborate).

73's
Richard Clark, KB7QHC

Two Meter FM Antenna Question
 

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

Two Meter FM Antenna Question
 

In that case, the gains are identical. A vertical "planted into the
earth" exhibits a higher gain (given many other considerations) than
an elevated vertical - be that elevated vertical be a dipole or a
ground plane design (which is simply another dipole, albeit rather
more elaborate).



I don't have much experience with earth verticals.... mostly HF I
would say, and that's another animal altoghther than the question the
original poster raised here on VHF antennas.

The vast majority of my experience with groundplanes and verticals is
at VHF and above. Every reference and factory specification for
standard grounplane and vertical dipole antennas I've seen indicates the
standard vertical dipole has a horizontal gain of 3 dBi, and the
groundplane 2.1 dBi. I don't know where some others are finding the
non-industry standard figures I have seen cited here.



Ed K7AAT

Two Meter FM Antenna Question
 

On 21 Aug 2006 22:07:40 GMT, Ed
wrote:

Every reference and factory specification for
standard grounplane and vertical dipole antennas I've seen indicates the
standard vertical dipole has a horizontal gain of 3 dBi, and the
groundplane 2.1 dBi.

Hi Ed,

Those are pretty curious references then. Why would they dwell on the
HORIZONTAL gains of VERTICAL antennas? There must be something left
unsaid in what you are trying to express because cross polarization
would drive down sensitivities by 20 to 30 dB.

For another matter, those values you quote bear very little
resemblence to typical 2M FM operation, unless it is from the Space
Shuttle. Height above ground variations in gain easily washes over
any differences you might perceive. I can see a variation of 2dB in
just raising a groundplane from 40" off the turf to 120".

73's
Richard Clark, KB7QHC