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Old May 21st 04, 05:48 AM
Dave VanHorn
 
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Default Directivity, with smooth sidelobes



What sort of antenna offers narrow beamwidth, combined with smooth
sidelobes?
I'm not too concerned with F/B ratio, or the magnitude of the sidelobes,
(smaller is better obviously) but I'm more concerned that they not be a mess
of deep spiky notches.

This is a somewhat special application above the 440 band, but I could scale
a 440/900/1296 design appropriately. Gain, per se, isn't really an issue,
and negative gain may in fact be acceptable.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet?


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Old May 21st 04, 11:33 AM
Fractenna
 
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What sort of antenna offers narrow beamwidth, combined with smooth
sidelobes?


I don't know what you mean by 'smooth sidelobes'.

Sidelobes are artifacts of truncation and/or lack of continuity, in the spatial
frequency spectrum of the aperture.

There are lots of ways, in hardware, to mitigate sidelobes. In an array this is
done, conventionally, by amplitude weighting of elements. There are
non-conventional ways of course, that are beyond the scope of this NG.

As elelemnts, there are moderate gain dipoles that have no sidelobes. A
conventional solution, for example, is a Landstorfer element, which is a curved
wire antenna that looks like a Gaussian in outline.

Perhaps a bit more specificity would help.

73,
Chip N1IR
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Old May 21st 04, 02:55 PM
Dave VanHorn
 
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Default

I don't know what you mean by 'smooth sidelobes'.

I would rather have a higher sidelobe amplitude, if I can also not have deep
notches in it, than lower sidelobes with deep notches, unless of course the
sidelobes can be made to be insignificant.
And at this point, I'm not sure how low they would have to be, to be
insignificant.

A small dish is possible, but given the wavelength, "small" is not really
all that small.
I don't get a choice on wavelength.
In order of importance, tight beamwidth, low sidelobes, "smooth" sidelobes,
and gain.

Sidelobes are artifacts of truncation and/or lack of continuity, in the

spatial
frequency spectrum of the aperture.

There are lots of ways, in hardware, to mitigate sidelobes. In an array

this is
done, conventionally, by amplitude weighting of elements. There are
non-conventional ways of course, that are beyond the scope of this NG.

As elelemnts, there are moderate gain dipoles that have no sidelobes. A
conventional solution, for example, is a Landstorfer element, which is a

curved
wire antenna that looks like a Gaussian in outline.

Perhaps a bit more specificity would help.


It probably would, but I'm just at the back of napkin stage on this project.
I won't know what I need really, till I do some testing.


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Old May 21st 04, 03:25 PM
Tam/WB2TT
 
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Default


"Dave VanHorn" wrote in message
...


What sort of antenna offers narrow beamwidth, combined with smooth
sidelobes?
I'm not too concerned with F/B ratio, or the magnitude of the sidelobes,
(smaller is better obviously) but I'm more concerned that they not be a

mess
of deep spiky notches.

This is a somewhat special application above the 440 band, but I could

scale
a 440/900/1296 design appropriately. Gain, per se, isn't really an issue,
and negative gain may in fact be acceptable.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet?

Because I don't want to read the same damn message 26 times.


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Old May 21st 04, 05:26 PM
Richard Clark
 
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Default

On Fri, 21 May 2004 10:25:10 -0400, "Tam/WB2TT"
wrote:
Q: Why is top-posting such a bad thing?

....
Because I don't want to read the same damn message 26 times.

Hi Tam,

You prove to be an example of your own grief. The poorest response
style is the one that does not edit the point responded to.

73's
Richard Clark, KB7QHC


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Old May 21st 04, 08:25 PM
Dave VanHorn
 
Posts: n/a
Default

You prove to be an example of your own grief. The poorest response
style is the one that does not edit the point responded to.


I am fairly mystefied as well.. Maybe he got a ton of copies somehow, but
there was only one on my server, and I only sent one.

Oh well.



  #7   Report Post  
Old May 21st 04, 11:22 PM
Tam/WB2TT
 
Posts: n/a
Default


"Richard Clark" wrote in message
...
On Fri, 21 May 2004 10:25:10 -0400, "Tam/WB2TT"
wrote:
Q: Why is top-posting such a bad thing?

...
Because I don't want to read the same damn message 26 times.

Hi Tam,

You prove to be an example of your own grief. The poorest response
style is the one that does not edit the point responded to.


Precisely, I think you got the point.

Tam

73's
Richard Clark, KB7QHC



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Old May 22nd 04, 12:58 AM
Tom Ring
 
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Default

You have too much time on

Tam/WB2TT wrote:

"Dave VanHorn" wrote in message
...


What sort of antenna offers narrow beamwidth, combined with smooth
sidelobes?
I'm not too concerned with F/B ratio, or the magnitude of the sidelobes,
(smaller is better obviously) but I'm more concerned that they not be a


mess

of deep spiky notches.

This is a somewhat special application above the 440 band, but I could


scale

a 440/900/1296 design appropriately. Gain, per se, isn't really an issue,
and negative gain may in fact be acceptable.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet?


Because I don't want to read the same damn message 26 times.



your hands.



tom
K0TAR


  #9   Report Post  
Old May 22nd 04, 02:16 AM
Dave VanHorn
 
Posts: n/a
Default


"Tom Ring" wrote in message
...
You have too much time on


Random text generator?


  #10   Report Post  
Old May 22nd 04, 02:30 AM
Tom Ring
 
Posts: n/a
Default

Dave VanHorn wrote:

"Tom Ring" wrote in message
...

You have too much time on



Random text generator?



You needed to read the whole post. It was a joke about the joke that is
the thread.

tom
K0TAR




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