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

art wrote:
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 ?

I lowered my 20m dipole from 40 ft. to 30 ft. because that gave
me a better skip into Arizona where a lot of my friends are.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil wrote -
I lowered my 20m dipole from 40 ft. to 30 ft. because that gave
me a better skip into Arizona where a lot of my friends are.

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

No Cecil, it didn't. It just gave you worse skip into where you didn't want
it.
---
Reg

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


I have always thought that if one changed the azimuth angle of a beam
it would improve a number of contact signals, pending the angle they
are reflected from the atmosphere.


--
Buck
N4PGW

So true ! Many a DXer loses signals because his TOA is to low
Art


"Cecil Moore" wrote in message
...
art wrote:
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 ?

I lowered my 20m dipole from 40 ft. to 30 ft. because that gave
me a better skip into Arizona where a lot of my friends are.
--
73, Cecil http://www.qsl.net/w5dxp


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News==----
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Newsgroups
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You can move the antenna boom up or down some 10 degrees and you would not
be able to tell the difference per
Lawson W2PV
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


I have always thought that if one changed the azimuth angle of a beam
it would improve a number of contact signals, pending the angle they
are reflected from the atmosphere.


--
Buck
N4PGW

Hi Art

I'd say that every little bit helps when conditions are marginal. Even
10dB extra mean pretty well nothing in readability when the signal is
already 20dB above the noise, but a few dB *can* make a difference when
the signal is in noise. Antenna efficiency and gain in the right
direction all helps but it is going to be a compromise. I mean if you
want to chat to the "locals" 30 degrees takeoff is better again!

I'll admit that I havent done any huge a amount of modelling on this but
(IMO) ground conditions and height over are far more important and are
very difficult to design an antenna for all situations. Maybe the trick
is to design your antenna for free space for "good" gain and then be
able to raise and lower it for the best angles..

Cheers Bob VK2YQA

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

"Bob Bob" wrote in message
news
Hi Art

I'd say that every little bit helps when conditions are marginal. Even
10dB extra mean pretty well nothing in readability when the signal is
already 20dB above the noise, but a few dB *can* make a difference when
the signal is in noise.
I don't see that! would not the S/N stay the same?




Antenna efficiency and gain in the right
direction all helps but it is going to be a compromise. I mean if you want
to chat to the "locals" 30 degrees takeoff is better again!

Agreed, that is what Cecil did.


I'll admit that I havent done any huge a amount of modelling on this but
(IMO) ground conditions and height over are far more important and are
very difficult to design an antenna for all situations.

For horizontal waves the ground conditions relative to 1 wavelength is of
little concern
Height as always helps with low TOA so one has to determine the average
incoming signal angle
of choice QSO's and design to suit.
Maybe the trick
is to design your antenna for free space for "good" gain and then be able
to raise and lower it for the best angles..

Agreed but I would like to see smaller turning radius ( moving away from the
boom length mantra , )
without the necessity for dual driven stacked array This would require a
fixed feed point with
moveable elements for desired TOA to suit desired QSO..
I am sure it can be done, and since 'every thing is
known about antennas' all that is reguired is for a Guru to come forward to
share how it is done.
Regards
Art


Cheers Bob VK2YQA

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

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

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

Hi Art

I'd say that every little bit helps when conditions are marginal. Even
10dB extra mean pretty well nothing in readability when the signal is
already 20dB above the noise, but a few dB *can* make a difference when
the signal is in noise.

I don't see that! would not the S/N stay the same?

Well to tell you the truth this was one of those "told by someone else"
things that I never did get around to proving myself (thinking it was
general knowledge) I have of course noticed it on 2M FM where the
recovered audio S/N falls off very rapidly as the usable senitivity of
the radio is reached. In that case a 1 or 2dB signal increase can make
the difference between readable 1 and readable 4. I have a funny feeling
the discussion I heard on the topic may have been on front end NF of
VHF/UHF receivers where a 1dB lower number there yielded a much larger
dB result. Note this was for SSB. I have some work to do here
understanding this. When I look at building another preamp for 2/70 I'll
do it then!

However if the noise is -110dBm and the signal was -114dBm, the margin
(s/n) would become less (of a negative number) when the signal level is
increased. You may not be able to resolve it but you can measure the
difference. You can of course use DSP techniques to resolve signals
weaker than noise. WRSS60 for example will enable you to resolve signals
26dB below the noise level. FSK441/JT44 is another example of signal
below noise reception.

For horizontal waves the ground conditions relative to 1 wavelength is of
little concern
Height as always helps with low TOA so one has to determine the average
incoming signal angle
of choice QSO's and design to suit.

Something about brewster angles and phase reversal in horizontal but not
vertical polarisation? (Note I work in IT, not RF!) I always thought
that the poorer the ground (eg sand/clay) the higher the takeoff angle
and over seawater was the lowest one could attain. (Keep in mind that VK
dropped CW earlier this year and I was one of those that has been
playing VHF+ for the last 25 years!)

Agreed but I would like to see smaller turning radius ( moving away
from the
boom length mantra , )
without the necessity for dual driven stacked array This would require a
fixed feed point with
moveable elements for desired TOA to suit desired QSO..

I would also expect that F/B & F/S are major contributors to design to.
Very handy when you neighbours son a few miles away wants to tune his VW
engine! I like the idea of a quad, simply because of its smaller turning
radius!

I once had a think about ways to tune a 3 element quad for best F/B.
Maybe some way to roll the wire up on a small motor shaft or tune it
with some C on the end of some tuned length feeder? Didnt figure out an
easy way to change the element spacing though. Maybe bending the
spreaders would have a similar effect of changing the feedpoint
positions on a stacked array?

You could also change the length of the phasing sections for a dual
driven stacked array - rather than moving the feedpoint. If I was
experimenting with this idea I'd probably start (modeling) with 3
parallel horizontal dipoles arranged such that when viewed from the ends
the (end point) shape was a triangle. All would be fed in parallel but
with different phase relationships between them.

I am sure it can be done, and since 'every thing is
known about antennas' all that is reguired is for a Guru to come forward to
share how it is done.

Not me sorry. If however I stumble onto something that defies all the
theory and works better than anyone else, this NG will be the first to
know - and I'll make the design like GPL software! Free...

Cheers Bob VK2YQA