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.



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".


Richard,

You and I seem to be talking different languages !! :^)

My reference to horizontal gain is gain measured in the horizontal
plane...... that is, measurements are taken broadside to the vertical
antenna elements, in this case, both the vertical dipole and a
groundplane.

Gain measurements taken in any other plane in any other plane than
horizontal tend to be rather useless since most VHF mobile communications
takes place horizontally..... even distant repeaters tend to be close to
the horizon.

Cross polarization is not an issue in VHF operations since all
commercial and amateur FM operations I'm familiar with use vertical
polarization.

As far as height variations having effect on gain.... you are
talking about path gain, or system gain. I am speaking specifically of
antenna gain, which I believed to be the question of the original poster.

And as I have already pointed out, most factory specifications
for vertical dipoles and groundplane antennas are as I already listed.

Ed K7AAT

On 22 Aug 2006 00:21:47 GMT, Ed
wrote:



And as I have already pointed out, most factory specifications
for vertical dipoles and groundplane antennas are as I already listed.

Ed K7AAT

Maybe I'm missing something, who manufactures vertical vhf dipoles?

bob
k5qwg

Maybe I'm missing something, who manufactures vertical vhf dipoles?

bob
k5qwg




Cushcraft used to sell one, amongst others. Most commercial
dipoles now are folded design, and designed for side mount on a tower or
mast, so gain figures tend to include the effects of the mast... although
they can be mounted on top of a tower or mast, too. Other than the
certain physical advantages inherent in folded dipole design, the
performance remains about the same as a standard halfwave dipole.

A quick check showed Andrew and Celwave (RFS Celwave) with current
products along these lines. Couldn't find a decent site for Cushcraft,
and didn't spend time looking for other vendors.

http://www.andrew.com/products/anten...a/DB220-B.aspx

http://shop.talleycom.com/store/product.jsp?
pdtl=_root&pdtl_pn=TELANT150D


Ed

Bob Miller wrote:
On 22 Aug 2006 00:21:47 GMT, Ed
wrote:



And as I have already pointed out, most factory specifications
for vertical dipoles and groundplane antennas are as I already listed.

Ed K7AAT


Maybe I'm missing something, who manufactures vertical vhf dipoles?

bob
k5qwg



I don't know about vertical dipoles for ham radio but many manufacturers
make them for marine applications. The vhf marine band antennas for
fiberglass boats are center fed vertical dipoles.

Dave WD9BDZ

"Bob Miller" wrote in message
...

snip


Maybe I'm missing something, who manufactures vertical vhf dipoles?

bob
k5qwg


US Navy has two, at least, NT-66095 for the VHF aircraft band and a
shortened version, NT-66095MOD, for the 160 MHz Marine band. Also, do a
Google search on "dipole sleeve" and "dipole cage" to see a few others.
Military also uses some biconical dipoles for receive only. They look like
two funnels, connected together at the skinny end and are all mounted
vertically for omni coverage, IIRC.

Would it be cheating to call the J-pole a vertical dipole? It is a
free-space half-wave radiator, albeit end-fed.

Sal M. Onella wrote:
"Bob Miller" wrote in message
...

snip

Maybe I'm missing something, who manufactures vertical vhf dipoles?

bob
k5qwg


US Navy has two, at least, NT-66095 for the VHF aircraft band and a
shortened version, NT-66095MOD, for the 160 MHz Marine band. Also, do a
Google search on "dipole sleeve" and "dipole cage" to see a few others.
Military also uses some biconical dipoles for receive only. They look like
two funnels, connected together at the skinny end and are all mounted
vertically for omni coverage, IIRC.

Would it be cheating to call the J-pole a vertical dipole? It is a
free-space half-wave radiator, albeit end-fed.



Actually it looks like a OCF dipole antenna to me.

Dave WD9BDZ

Maybe I'm missing something, who manufactures vertical vhf dipoles?


We're hams. We make our own antennas, don't we?
Two pieces of wire, and some insulators.

I had a vertical dipole for 2 meters once, a section of an old tv
antenna. One element (by definition) mounted on an insulator on a
boom. I attached the boom with two hose clamps onto my tower and
mouunted the single element out from the tower 3-4 feet. Attached a
piece of coax to the elements. Zero cost, used it for 15 years like
that.

Worked great. Wait a minute. On second thought how would I know
that? Ok let me rephrase that. "It worked." It's 2 meters, for
crying out loud - anything works. If you need gain you get a beam.

Rick K2XT

On Wed, 23 Aug 2006 03:41:41 GMT, (Rick) wrote:



Maybe I'm missing something, who manufactures vertical vhf dipoles?


We're hams. We make our own antennas, don't we?
Two pieces of wire, and some insulators.

I agree, a 2 meter dipole would take minutes to make. I was just
curious about manufacturer's published gain figures since I can't
recall ever seeing a manufactured 2 meter center-fed dipole --
apparantely there are a few out there.

bob
k5qwg


I had a vertical dipole for 2 meters once, a section of an old tv
antenna. One element (by definition) mounted on an insulator on a
boom. I attached the boom with two hose clamps onto my tower and
mouunted the single element out from the tower 3-4 feet. Attached a
piece of coax to the elements. Zero cost, used it for 15 years like
that.

Worked great. Wait a minute. On second thought how would I know
that? Ok let me rephrase that. "It worked." It's 2 meters, for
crying out loud - anything works. If you need gain you get a beam.

Rick K2XT

I was always under the impression the 2.15 dBi and 3 dBi applied to antennas
in free space, the GP being on one side of an infinite plane at the fed end.
Indeed in real would cases in the vicinity of earth or other large (relative
to the antenna) objects the differances (particularly in FM service) become
negligable. Note too: dBi is relative to a (theoretical) isotropic radiator
(which is a mathamaticily logical standard of comparison), vs. dBd which is
relative to an ideal center fed 1/2 wave dipole in free space.


"Ed" wrote in message
. 192.196...

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.



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".


Richard,

You and I seem to be talking different languages !! :^)

My reference to horizontal gain is gain measured in the horizontal
plane...... that is, measurements are taken broadside to the vertical
antenna elements, in this case, both the vertical dipole and a
groundplane.

Gain measurements taken in any other plane in any other plane than
horizontal tend to be rather useless since most VHF mobile communications
takes place horizontally..... even distant repeaters tend to be close to
the horizon.

Cross polarization is not an issue in VHF operations since all
commercial and amateur FM operations I'm familiar with use vertical
polarization.

As far as height variations having effect on gain.... you are
talking about path gain, or system gain. I am speaking specifically of
antenna gain, which I believed to be the question of the original poster.

And as I have already pointed out, most factory specifications
for vertical dipoles and groundplane antennas are as I already listed.

Ed K7AAT