Amen.
Let us use TOA for the elevation angle where an antenna's pattern is
strongest and ATOA for the actual elevation angle used over a long HF path.

At least from 7 MHz to 21 MHz, when DX ionosphere propagation is likely
the ATOA is between about 12 degrees and about 2 degrees. When comparing
antennas to be used for HF DX contacts, it is appropriate to note the gain
at 3, 6, and 9 degrees as being the numbers to compare. The actual TOA (as
defined above) is only interesting.

That said, it is possible to have a single horizontally polarized
antenna that is so high that it suffers in comparison to a lower antenna for
ATOAs of about 10 degrees (by more than the one db that is being talked
about). For one horizontally polarized antenna to be used for DX contacts
the desired heights are two to three wavelengths above earth.

If one can use a plurality of horizontally polarized antennas,
interesting results are possible. For instance: on receive, combining a
lower second antenna with a tall first antenna can effect the approximate
cancellation of the second lobe. The second lobe has a high TOA and can
contribute significantly to the noise and interference received from
relatively short distances. Nulling the second lobe can significantly
increase the received SNR.
For closer spacing of multiple antennas, one can effect more gain than
that of one antenna - with trade-offs.

I emphasize what has been said by Roy and others: TOA (as defined
above) is interesting, but it is not the most important number for DX
contacts.

73 Mac N8TT


--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Roy Lewallen" wrote in message
...
I say ignore the TOA. (For those unfamiliar with the term, it's the
"takeoff angle", which usually means the elevation angle at which the
antenna pattern is strongest.)

What counts is the gain at the elevation angle at which you want to
communicate. This, in turn, depends on the distance and the propagation
conditions. If you need a strong signal at an elevation angle of 15
degrees, it doesn't matter whether the TOA is 10 degrees, 15, or 20 or
zero. All that counts is the gain at 15 degrees. And an antenna with TOA
of 15 degrees doesn't necessarily have the most gain at 15 degrees of
any antenna.

Consider the following three 40 meter antennas: A vertical antenna with
about 8 radials (18 ohm ground system resistance), a dipole at 30 feet,
and a dipole at 40 feet, all over average ground.

Antenna TOA deg Gain at 26 deg. Gain at 15 deg.

Vert 26 -1.76 dBi -2.72 dBi
Dipole @ 30' 90 (straight up) 2.58 dBi -1.28 dBi
Dipole @ 40' 51 3.9 dBi 0.32 dBi

-- Which one has the lowest takeoff angle?
-- Which one is the best for communicating at 26 deg. elevation angle?
-- Which one is the best for communciating at 15 deg. elevation angle?

What does the takeoff angle have to do with which antenna is best?

Roy Lewallen, W7EL

On Sat, 29 Jan 2005 17:04:14 GMT, "
wrote:

Buck, in my posting I refered to 20 meters and also the incoming angles and
average signals thereof coming from Europe. Thus my interest was in the
lower half of the main lobe. The thickness of the lobe of the lobe would
thus not be important,
only the contour of the underside of the lobe. It is this portion of the
lobe where a DXer referers to the fact that a db means a lot as opposed to
adding a db gain to angles contained within a lobe. Note that the thickness
of the lobe can vary even tho both anternnas may have the same take of angle
as can be seen by comparing a monster boom length antenna to that of a
stacked beam which admittedly has a feed point which is very high. When
comparing these two types an optimum would be a low feed point (1 WL) with a
small turning radius with means to compress the main lobe downwards for
those DX
signals arrive and where the 'silly' db becomes everything
Regards
Art.




"Buck" wrote in message
.. .
On 28 Jan 2005 12:48:52 -0800, "art" wrote:

Most people have added an amplifier only to find out that the
difference in signal
was very small. Thus many people deride the value of a 'silly' db gain
whereas DX'ers say that a single db extra is a lot !
Fact is that most long distance signals on 20 metres come in at angles
of 11 degrees or less where as the 'normal' antenna has a TOA of around
14 degrees.
So where a dxer points to the extra 1db gain as being everything in
fact it is the lowering of the TOA that comes with the extra gain. In
my opinion if one designs his antenna for a lower TOA say 10 to 11
degrees then even tho its gain may well be below the dxers choise( a
very long boom or stacked antennas) the lower TOA with less gain will
show little difference
to the antenna of choics because the lower edge of the radiation lobe
will follow the same line and any extra gain provided will have the
same effect of adding an amplifier which is minimal compared to the
ability of capturing signals that arrive at low angles.
I believe it is time for antenna designers to concentrate less on
obtaining gain and instead concentrate more on lowering the TOA.
without the need of excessive real estate requirements.
What say ?
Art

Someone correct me if I am wrong, but isn't gain derived by narrowing
focussing all the energy into a more narrow path?

Besides, TOA is important to the location of an antenna in respect to
its relative position to the ground and the surrounding terrain.

I have heard that people surrounded by mountains prefer a 1/4 whip on
their cars for 2 meters and up when trying to hit repeaters due to its
higher angle of radiation, but in the flat areas, the preferred
antennas are the 5/8 wave etc due to its horizontal gain.

Being on the side of a hill, I can't use an antenna at roof-top level
with a low angel of radiation as there isn't enough power to get the
signal through the miles of land mass under my neighbor's houses.

I did an experiment when I first received my General license to see if
I could sign into the GA SSB NTS Net. I rolled out a spool of wire on
the ground approximately 1/4 wave for 3975 kc. Without a tuner I was
able to get acceptable SWR and checked into the net. I wasn't the
strongest signal but I did well enough to hold several QSOs. It
wasn't as good as my dipole when I raised one, but it worked better
than my 40 meter dipole at the time.

I believe that a horizontal dipole will have about the same TOA as a
vertical dipole when both are sufficiently high. However, the dipole
is more bidirectional and the vertical is omni directional. Therefore
the horizontal dipole may display some gain broadside over the
vertical.

I believe that Cecil's picture reinforces the idea that on HF
especially, the TOA is largely affected by the antenna's elevation
above ground.

However, I was reading in CQ or QST last year about a DX operator who
uses verticals near the sea and wins his contests because of his
antennas. He finds the best location for his antennas near the ocean.
I believe he said he had tried beams before but there is an ocean
effect that makes the verticals better suited for his operations.

That same vertical would be lousy for me as my house is on a hill that
forms a very close valley.

I used a Taylor Radio vertical years ago in this yard and it sucked.
However, when I used it in Charleston and Jacksonville, it was
fantastic (not near the ocean).

Another DX operator suggests that most people will have a better
chance of communicating with him if they use a slanted dipole pointed
in the direction of their QTH. The angle of radiation and gain make
it a great DX antenna.

Different antennas work differently depending on their locations. I
think your better question would be, what is the best antenna for my
QTH and operating style?




--
Buck
N4PGW




Ok, Art,

I think I am with you now. I just re-read all the previous posts.
Roy Lewallen first referred to the 40 meters and I think he introduced
the picture of the angles from a vertical and a dipole.

Sorry to have been so slow picking up on this, and thank you all for
your patience with me. With all this discussion, I am learning. I
echo back my thoughts at the time that may be subject to change upon
correction or even possibly due to misinformation, hihi.

I have been studying antenna theory for a while now, off and on. Not
like a college professor, just on my own. Let's start by getting back
to your original post.

You are interested in DXing on 20 meters in which most signals come in
at 11 degrees or less. Therefore antenna designers should focus their
attention, not on antenna gain, but on getting the gain to the
incident angle of radiation. You mentioned that Amps turn out to be
of little help if the antenna angle is wrong. (I'll save the amp for
another discussion and deal with the antennas.)

I have been studying about antennas for a while now. (not like a
college professor, probably more accurately I have been reading a
lot.) I understand what you are saying about the amplifier. From my
experience I have learned a simple truth. Either one has the
propagation to make a contact, or one doesn't make contact. Last year
I totally surprised myself when I called a DX station in a pileup and
he answered. I was running an FT-817 into a dipole about 65 feet
high. There have been times I couldn't break a pileup with a 400 watt
Swan on the same antenna.

Getting back to your topic, from what I understand, the terrain and
antenna elevation are as, or more, important in establishing the angle
of incidence as the antenna is. IIRC, a Yagi has a recommended
minimum height above terrain for optimum operation. I believe that 20
meters is 125 feet.

BTW, I am curious to know, from where did you get the information that
the incoming signals are at 11 degrees?

Speaking of Yagi's and gain, I know that the gain (and inversely the
bandwidth) of a yagi is increased by extending the spacing between
elements. A wide spaced gives a little more gain than narrow spaced
elements. I believe it also narrows the beam width of the signal. I
don't think it affects that TOA, though, except maybe by its
relationship to the ground and its surrounding terrain.


--
Buck
N4PGW

On Sat, 29 Jan 2005 19:22:12 -0500, Buck wrote:

Speaking of Yagi's and gain, I know that the gain (and inversely the
bandwidth) of a yagi is increased by extending the spacing between
elements. A wide spaced gives a little more gain than narrow spaced
elements. I believe it also narrows the beam width of the signal.

Hi Buck,

This is fine.

I don't think it affects that TOA, though, except maybe by its
relationship to the ground and its surrounding terrain.

It is unlikely that anything you do in such a small footprint will
bring any geometric change that brings even a perceptible change to
the TOA. However, by simply increasing gain, the entire lobe
structure of the antenna increases (same shape balloon, but now a
larger balloon) which does impact the TOA; but not its angle, instead
more its magnitude. This, in a sense, was the comparison Roy was
drawing upon with the different examples.

In a sense, increasing the antenna gain (all other factors held
constant) would be indistinguishable from simply boosting the
transmitter gain (or adding an Amp).

73's
Richard Clark, KB7QHC

On Sat, 29 Jan 2005 15:35:21 -0500, "J. Mc Laughlin"
wrote:

73 Mac N8TT


Let me re-iterate what you said, assuming I understand it.

Art is saying that it is better to have a more accurate TOA than the
last db of antenna gain, but you are saying that a better s/n ratio
(as handled by the antenna) is better than the last db of gain.

Of course, Art started his statement with something about a person
turning up their amplifier and having no better results. Therefore he
must also be considering being heard as well as hearing. I would
think that an amplifier will, for the most part, increase the
radiation strength of every angle radiated at all by the antenna. If
the amp represents a 6dB gain over the radio, it will represent a 6 dB
gain in the any direction in which the lobe points. At least for the
transmission, that should provide the 1 db difference we are talking
about.

This doesn't address that time of day in which the west hears from the
east in one way propagation.

Correct me if I am wrong here.


--
Buck
N4PGW

Just to clarify -

The angle of elevation of the radio path between points A and B on the
Earth's surface is always a constant which depends purely on the Earth's
geometry and the number of hops.

It has nothing to do with the radiation patterns, beam widths of either the
receiving or transmitting antennas, vary as they may.

There may of course be short term variations due to ionospheric effects.
---
Reg

Dear Buck (N4PGW):

I am having a difficult time finding what I thought that I said in your
paraphrasing. Your bio on QRZ.COM does not indicate an interest in DX, so
it is possible that all of my comments were misdirected.

Perhaps the essence of what I was trying to say, in addition to agreeing
with Roy, is that it is desirable with (single) horizontally polarized
antennas at HF to have as much gain as possible appear in the direction that
is expected to be used for DX contacts. In turn, that suggests that it is
desirable to have a height above ground (or above the applicable "refection"
area) be between 2 and 3 wavelengths.

I do not recall writing anything about power amplifiers or something
called "one way propagation."

73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Buck" wrote in message
...
On Sat, 29 Jan 2005 15:35:21 -0500, "J. Mc Laughlin"
wrote:

73 Mac N8TT


Let me re-iterate what you said, assuming I understand it.

Art is saying that it is better to have a more accurate TOA than the
last db of antenna gain, but you are saying that a better s/n ratio
(as handled by the antenna) is better than the last db of gain.


snip
Correct me if I am wrong here.


--
Buck
N4PGW

On Sat, 29 Jan 2005 16:45:29 -0800, Richard Clark
wrote:

On Sat, 29 Jan 2005 19:22:12 -0500, Buck wrote:

Speaking of Yagi's and gain, I know that the gain (and inversely the
bandwidth) of a yagi is increased by extending the spacing between
elements. A wide spaced gives a little more gain than narrow spaced
elements. I believe it also narrows the beam width of the signal.

Hi Buck,

This is fine.

I don't think it affects that TOA, though, except maybe by its
relationship to the ground and its surrounding terrain.

It is unlikely that anything you do in such a small footprint will
bring any geometric change that brings even a perceptible change to
the TOA. However, by simply increasing gain, the entire lobe
structure of the antenna increases (same shape balloon, but now a
larger balloon) which does impact the TOA; but not its angle, instead
more its magnitude. This, in a sense, was the comparison Roy was
drawing upon with the different examples.

In a sense, increasing the antenna gain (all other factors held
constant) would be indistinguishable from simply boosting the
transmitter gain (or adding an Amp).

73's
Richard Clark, KB7QHC


I think you and I are in agreement except for what Art believes. (see
his statement below:)

I believe it is time for antenna designers to concentrate less on
obtaining gain and instead concentrate more on lowering the TOA.
without the need of excessive real estate requirements.

He agrees that the antenna is better as it improves receive as well as
transmit, but I can't see the TOA being more important than the gain
unless it is really off by a long way. An NVIS antenna has a
different purpose than a DX antenna so he would need an antenna that
fits his needs. I am not sure what would reduce the TOA over a Yagi
unless it is a Yagi pointed downward.

Maybe what we need to be doing is asking Art what his situation is and
trying to find the antenna that best fits his needs. I can't help but
think that this question arose because he can't seem to find the
antenna that helps him make successful DX contacts.

I used a TA-33JR for years. It was a fantastic 3 element beam. It
was small, fit on my roof and could be turned by a RadShak TV Rotor.
Even though it wasn't the ideal height above ground, it made a world
of difference chasing mobiles for the WA counties award.

I try to learn a lot about antennas. I don't claim to be an expert
and certainly don't want anyone to think I am trying to make Art (or
anyone else) look like they don't know what they are talking about.

BTW, Art, have you looked at the N4GG antenna? It is on the ARRL site
for members. I built one and didn't understand it so I took it down
and made a new antenna. Then I got the details of it, but it was
promoted as being a low angle of radiation. I don't know the degrees,
though. It was certainly a much quieter antenna than the dipole.

I talked to N4GG by email. He is a real nice person.

Good luck,

Buck


--
Buck
N4PGW

I occasionally chase counties when I am sitting at my desk doing other
things and have the radio available. Right now I am using a
horizontal dipole antenna to make contacts. The downside of this is
that many times I can't hear the mobiles or they can't hear me.

I am thinking that I might be able to improve my contacts by using a
vertical antenna since most mobiles use vertical antennas. I have
heard that once the signal bounces off the ionosphere, polarity isn't
as important as it is for local communications. However, when I was
assembling a 2 meter dipole antenna, I held it horizontal and turned
it vertical. I saw the s-meter go from nothing to s-7 and the
repeater go from silent to full quieting when I did this. I can't
help but wonder how much difference it will make with the mobiles.

Thanks for the comments.

Buck
N4PGW

--
Buck
N4PGW

Yes, you've got it. Hopefully some of the folks who didn't understand my
explanation will understand yours.

Roy Lewallen, W7EL

Mike Coslo wrote:

Let me have a shot at it, Roy.

possible blather alert!

Perhaps there is confusion by some people with the idea that the
takeoff angle. I suspect that a lot of people think of their RF leaving
the antenna as a "blob" that leaps out at some desired or undesired angle.

Instead, the RF is heading off in all directions, with some angles
having more relative power.

So even if an antenna has a lower TOA, it might be less gain than an
antenna that has a higher TOA has at that angle.

An inefficient antenna with a low TOA can be less efficient at that
low TOA than a more efficient antenna with a higher TOA is at that same
low TOA.

Oy.

- Mike KB3EIA -

rest snipped

Thanks, Cecil.

Roy Lewallen, W7EL

Cecil Moore wrote:

Maybe a picture is worth a thousand words. Here's a comparison
radiation pattern for my 130 ft dipole Vs my 40m vertical with
elevated radials. In the dipole's favored direction, it's TOA
is greater than the vertical's yet the dipole radiates more
power than the vertical even at the vertical's TOA. Here's the
pictu http://www.qsl.net/w5dxp/dipvsver.htm
--
73, Cecil, W5DXP