Parabolic Dish Templates made easy - Page 3

RF addict · 10-02-2005

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.

RF addict · 10-02-2005

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

The measurements are 9" across and 1.5" deep.

Airstreamer · 10-02-2005

Quote:

Originally Posted by RF addict

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!

RF addict · 10-02-2005

Quote:

Originally Posted by Airstreamer

/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.

RF addict · 10-04-2005

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

streaker69 · 10-04-2005

Quote:

Originally Posted by RF addict

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

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.

RF addict · 10-04-2005

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.

RF addict

Airstreamer · 10-04-2005

Quote:

Originally Posted by 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!

Scruge · 10-05-2005

@ 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.

Tholek · 12-31-2005

For a poor man's alternative, try using the sconce-like dish from floor lamps tossed out by neighbors. Some seem pretty parabolic.

theboss · 01-16-2006

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

Mark57 · 01-16-2006

Quote:

Originally Posted by theboss

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

No idea. I was able to get it just now.

phlogiston · 01-30-2006

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.

Scruge · 01-30-2006

Quote:

Originally Posted by phlogiston

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.

phlogiston · 01-30-2006

Quote:

Originally Posted by Scruge

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.

01-30-2006	#43 (permalink)
phlogiston caffeine ninja Join Date: Jan 2006 Location: Idaho, USA Posts: 6	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. Last edited by Thorn : 01-31-2006 at 04:43 AM.

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10-02-2005	#31 (permalink)
RF addict Registered Member Join Date: Aug 2003 Location: Flyover Country Posts: 39	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.

10-02-2005	#32 (permalink)
RF addict Registered Member Join Date: Aug 2003 Location: Flyover Country Posts: 39	According to my calculations with the spreadsheet the focal point should be at 4 inches. The measurements are 9" across and 1.5" deep.

10-04-2005	#35 (permalink)
RF addict Registered Member Join Date: Aug 2003 Location: Flyover Country Posts: 39	I'm finished with the first one. It seems to work really well. I'm seeing ap's that nothing else did from here.

10-04-2005	#37 (permalink)
RF addict Registered Member Join Date: Aug 2003 Location: Flyover Country Posts: 39	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. RF addict

10-05-2005	#39 (permalink)
Scruge Nyuk nyuk! Join Date: Jan 2005 Location: TX Posts: 1,355	@ 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.

12-31-2005	#40 (permalink)
Tholek Registered Member Join Date: Nov 2004 Posts: 17	For a poor man's alternative, try using the sconce-like dish from floor lamps tossed out by neighbors. Some seem pretty parabolic.

01-16-2006	#41 (permalink)
theboss Registered Member Join Date: Jan 2006 Posts: 1	ok im logged in and cant download the spread sheet.. why??