Parabolic Dish Templates made easy

Configuration and other hardware related information

Postby RF addict » Sat Oct 01, 2005 11:03 pm

Not yet but I'll do it now. Thanks for the reminder.

I did do the cheezy aluminum foil light test with a bright lamp and it seemed to focus out at around 15 cm.
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Postby RF addict » Sat Oct 01, 2005 11:11 pm

According to my calculations with the spreadsheet the focal point should be at 4 inches.

The measurements are 9" across and 1.5" deep.
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Postby Airstreamer » Sun Oct 02, 2005 12:50 pm

RF addict wrote:Not yet but I'll do it now. Thanks for the reminder.

I did do the cheezy aluminum foil light test with a bright lamp and it seemed to focus out at around 15 cm.




/slap forehead HARD with palm!

(Sheepish) Why didn't I think of that!
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And the Gods of the Copybook Headings said: "Stick to the Devil you know.""

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Postby RF addict » Sun Oct 02, 2005 5:25 pm

Airstreamer wrote:/slap forehead HARD with palm!

(Sheepish) Why didn't I think of that!



I don't know "doc" you could've avoided all those nasty numbers and math. ;)
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Postby RF addict » Tue Oct 04, 2005 7:08 pm

I'm finished with the first one. It seems to work really well. I'm seeing ap's that nothing else did from here.

Image


Image
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Postby streaker69 » Tue Oct 04, 2005 7:11 pm

RF addict wrote:I'm finished with the first one. It seems to work really well. I'm seeing ap's that nothing else did from here.

Image


Image


Damn, Really nice work. They look like you really took your time and did a damn fine job. You should sell em, if you could get one tested to find out what it's actual db gain is and it's transmission pattern.
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Postby RF addict » Tue Oct 04, 2005 7:33 pm

Thank you!

I'll try to do as much testing as I can. If you have any ideas or suggestions to establist a rough number for the gain I will try to see what it is.

The main problem with building multiple units is the stand. I only had one and found it in some junk. Also, it probably cost more than the materials for five of these things.


I have some ideas for other mounts in mind for the next one.


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Postby Airstreamer » Tue Oct 04, 2005 10:21 pm

[quote="RF addict"]I don't know "doc" you could've avoided all those nasty numbers and math. ]


Like it says... Sniffin' the aether.
Must have had too many sniffs today!

:p
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Postby Scruge » Wed Oct 05, 2005 8:32 am

@ RF addick

That came out nice. What did you use for the collar holding the pvc pipe? I've not seen those before.

I'm guessing your gain is around 10-12dbi, based on an aperture of 8.5". FYI the larger outside metal ring isn't part of the parabolic curve's surface and neither are the spokes at the center. Only the surface area represented by the spiral wound wire should be used for depth and diameter measurements. I think if you factor those differences in you'll see the gap between the empirical and theoretical focal points converge.

You might also want to rig a means to adjust the focal point to find the best setting.
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Postby Tholek » Sat Dec 31, 2005 3:07 am

For a poor man's alternative, try using the sconce-like dish from floor lamps tossed out by neighbors. Some seem pretty parabolic.
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Postby theboss » Mon Jan 16, 2006 3:12 am

ok im logged in and cant download the spread sheet.. why??
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Postby Mark57 » Mon Jan 16, 2006 5:01 am

theboss wrote:ok im logged in and cant download the spread sheet.. why??


No idea. I was able to get it just now.
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Postby phlogiston » Mon Jan 30, 2006 1:37 am

Scruge - Thanks for the template! No Google query I've tried gave such a concise answer to my question. With this I was able to make a rough parabolic LLPR from foamboard and aluminum tape held together with hot glue. At the focal point, I use a stock USB adapter.

http://img74.imageshack.us/img74/5882/test13cx.jpg

The initial results were very good - better then any of the other homemade antennas I have yet tried.
I intend to make a larger, more precise version. My question is this: Assuming that I want to make a connection with a distant AP, and not passively listen, would making a deep reflector with a focal point far inside the "dish" direct more energy to the AP then a shallow dish with the focal point outside the depth? I assume that the dipole I intend to use radiates evenly in 360 degrees from the polarity, and having it inside would reflect more in the direction I want, but I havn't seen any designs to this effect anywhere.
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Postby Scruge » Mon Jan 30, 2006 6:13 am

phlogiston wrote:I intend to make a larger, more precise version. My question is this: Assuming that I want to make a connection with a distant AP, and not passively listen, would making a deep reflector with a focal point far inside the "dish" direct more energy to the AP then a shallow dish with the focal point outside the depth? I assume that the dipole I intend to use radiates evenly in 360 degrees from the polarity, and having it inside would reflect more in the direction I want, but I havn't seen any designs to this effect anywhere.

I'm not an expert but from what I understand changing the depth of the dish will only affect its directional properties. A deep dish will be less susceptible to adjacent noise and signals, whereas a shallow dish will exhibit some omni directional properties.
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Postby phlogiston » Mon Jan 30, 2006 7:59 am

Scruge wrote:I'm not an expert but from what I understand changing the depth of the dish will only affect its directional properties. A deep dish will be less susceptible to adjacent noise and signals, whereas a shallow dish will exhibit some omni directional properties.

Thanks. That makes sense.
I'm sure that this question could be answered on paper or with a simulation, but I wouldn't know where to begin. Perhaps I should have paid more attention in math class:) I guess I'll just have to make one of both with the same diameter, but very different shapes and see what happens. Next paycheck, that is.
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