Parabolic Dish Questions
 

amdx wrote:
I was going to attempt this but I don't know how to calculate the area (A)
of my non circular dish. Any help there?

Calculus? Graphic solution?
--
73, Cecil http://www.w5dxp.com

Parabolic Dish Questions
 

Area = PI*a*b, as defined below.

http://en.wikipedia.org/wiki/Ellipse

Frank


"Cecil Moore" wrote in message
...
amdx wrote:
I was going to attempt this but I don't know how to calculate the area
(A)
of my non circular dish. Any help there?

Calculus? Graphic solution?
--
73, Cecil http://www.w5dxp.com

Parabolic Dish Questions
 

amdx wrote:
I have a Directv dish 35 inches wide x 20 inches tall 4inches deep.
I calculated the focus as F=D*2 / 16d where D =diameter and d=depth
F=18 inches Ok so far.
How do you find beamwidth? I think the 35" dimensiom would have a tighter
pattern than the 20 ", but how do you calculate,

Second, The feed antenna, There can be different feeds.
A simple monopole, dipole, biquad, patch, yagi, helix.
How does the feed antenna affect the gain of the dish, if at all?
Yea, it my be difficult to light the yagi or helix, so if you like throw
those out.
Thank You,
Mike

Some guys at the local club were trying to use a TV dish like yours.
They eventually decided it was easier to build a dish from scratch.
The old TVRO dishes can be useful and there are plenty of them around
that can be had just for the asking.

Jimmie

Parabolic Dish Questions
 

"Frank" wrote in message
news:0R89k.658$7%6.42@edtnps82...
Area = PI*a*b, as defined below.

http://en.wikipedia.org/wiki/Ellipse

Frank
Thanks Frank,
From the wiki "The area enclosed by an ellipse is ?ab, where (as before) a
and b are the ellipse's semimajor and semiminor axes."
Now back to, why did I want to now that.
Mike

Parabolic Dish Questions
 

Some guys at the local club were trying to use a TV dish like yours.
They eventually decided it was easier to build a dish from scratch.
The old TVRO dishes can be useful and there are plenty of them around
that can be had just for the asking.

Jimmie
I don't know why it would be easier to build one, but yes, I ask and got
three different dishes, so I stopped asking.
Mike

Parabolic Dish Questions
 

"amdx" wrote in message
...


Some guys at the local club were trying to use a TV dish like yours.
They eventually decided it was easier to build a dish from scratch.
The old TVRO dishes can be useful and there are plenty of them around
that can be had just for the asking.

Jimmie
I don't know why it would be easier to build one, but yes, I ask and got
three different dishes, so I stopped asking.
Mike

Hi Mike I missed the post where you said why you wanted the dishes and
what you intend to use them for. What do you intend to use the dishes for?

Jerry KD6JDJ

Parabolic Dish Questions
 

"Jerry" wrote in message
news:2rc9k.26$HY.21@trnddc01...

"amdx" wrote in message
...


Some guys at the local club were trying to use a TV dish like yours.
They eventually decided it was easier to build a dish from scratch.
The old TVRO dishes can be useful and there are plenty of them around
that can be had just for the asking.

Jimmie
I don't know why it would be easier to build one, but yes, I ask and got
three different dishes, so I stopped asking.
Mike

Hi Mike I missed the post where you said why you wanted the dishes and
what you intend to use them for. What do you intend to use the dishes
for?

Jerry KD6JDJ
I didn't say.

Oh, ok. I want to increase the strength of a wifi signal.
Mike

Parabolic Dish Questions
 

"amdx" wrote in
:

....
I didn't say.

Oh, ok. I want to increase the strength of a wifi signal.


Gee, getting relevant information from you is a chore, and you seem to
delight in supplying a partial picture.

Now, what frequency WiFi?

If you are thinking of 2.4GHz, you must already have worked out a feed
solution that efficiently illuminates the small dish, a considerable
challenge.

While you are obsessing about calculating the area of an elipse, you
haven't had a look at the disk from the distant end, have you? It is
probably very close to circular in cross section when viewed from afar in
the direction of the beam.

When you have worked through some of this, you might see why offset feed
dishes made for Ku band aren't widely used by informed people at 2.4GHz.
Of course, there will always be the 'innovaters' with a USB wireless
stick pointing at a garbage tin lid or wok... but that says it all,
doesn't it!

Owen

Parabolic Dish Questions
 

Gee, getting relevant information from you is a chore, and you seem to
delight in supplying a partial picture.

Now, what frequency WiFi?

If you are thinking of 2.4GHz, you must already have worked out a feed
solution that efficiently illuminates the small dish, a considerable
challenge.

While you are obsessing about calculating the area of an elipse, you
haven't had a look at the disk from the distant end, have you? It is
probably very close to circular in cross section when viewed from afar in
the direction of the beam.

When you have worked through some of this, you might see why offset feed
dishes made for Ku band aren't widely used by informed people at 2.4GHz.
Of course, there will always be the 'innovaters' with a USB wireless
stick pointing at a garbage tin lid or wok... but that says it all,
doesn't it!

Owen
Thanks, Owen
Mike

Parabolic Dish Questions
 

amdx wrote:

...
I didn't say.

Oh, ok. I want to increase the strength of a wifi signal.
Mike

You will probably find a lot of help if you "nose" around your local
college (computer/physics/engineering instructors can point you to the
best minds.) The youngsters are all into stretching wifi distances to
the max.

Here is a page to get you started:

http://www.engadget.com/2005/11/15/h...-dish-antenna/

After experimenting with many different antennas at the feed point, I
kept the biquad in the original plans. Your dish is larger than the one
I use (mine is identical to the one on the page--my feed is slightly
modified ...)

Regards,
JS