finally attempting to build one of the fab-corp antennas

godsmoke · 08-10-2002

Hi all...

Well, after some debating, I think I might attempt to build one of those 5 dbi magmounts. Thank you to outcast_one for posting pics of his magmount antenna.

These pics can be found here: http://forums.netstumbler.com/showth...&threadid=2034

Anyway, after looking at suggestions, (since the second most important part of that antenna is the ground plate) I decided that I would use a hard drive plate. It took some looking for screwdrivers and busting a drill bit -- but I got one of the plates out, and plan to use it in my design. I'm going to be posting pics on my website (www.godsmoke.com/antenna.html) in about a week when I get the time to sit down and build the thing. Anyone know what kind of metal to use? Where might I get this metal? (for antenna post)

Thank you for all your help...

-godsmoke

blackwave · 08-10-2002

Quote:

Originally posted by godsmoke
I decided that I would use a hard drive plate.

You are using a hard drive platter for a ground plane? Did you read about using this somewhere or did you just make it up out of convenience. I didn't think the composite of a hard drive platter would be substantial enough to account for any type of constant, especially for any type of RF usage.

godsmoke · 08-10-2002

Hi,

yeah, you make a good point -- I have no idea about how it might work (well or not) -- thought it might be worth a shot. I got the idea from this website -- where someone has built a clone of the fab-corp

http://www.geocities.com/lincomatic/homebrewant.html

let me know about your ideas

I think I'm gonna buy the fab-corp anyway...though I live in manhattan, NYC, so I don't think finding WAPs will be too hard.

-godsmoke

blackwave · 08-10-2002

Quote:

Originally posted by godsmoke
let me know about your ideas

Ah lincomatic's site, and sparafina's idea... I thought I played around with platters as rf... maybe only certain platters?

sparafina · 08-10-2002

You can use wires (radiator+5%) as a groundplane arrayed around the antenna/radiator at 90 degrees. You could also use an old cd if you want. A car hood also works.

godsmoke · 08-10-2002

hmm ... this sounds like it would work -- but I'm just wondering what you mean exactly, could you provide a diagram or picture?

Would the hard drive plate work -- I already broke a bit and so forth to get a hard drive plate out. it's a good size...

-godsmoke

fordem · 08-10-2002

Quote:

Originally posted by sparafina
You could also use an old cd if you want

I thought the ground plane had to be metal?

sparafina · 08-10-2002

Quote:

Originally posted by fordem

I thought the ground plane had to be metal?

the shiny stuff is a thin foil, that's why it's so much fun to micowave them. Try a simple experiment, turn on netstumbler and look at signal loss when you put various materials between the card and the AP.

godsmoke · 08-10-2002

I would think so...

Yeah, I mean if a hard drive doesn't work -- then I have no idea how a cd would work. it has to be accepting the radio signals which is something cds (plastic) do NOT do well...

Anyway...

Anyone every used a hard drive plate for a ground plane?? Success? Failure? Tell me how it turned out...

lincomatic · 08-10-2002

i think you are making too big a deal about the ground plane. i just used a tin can lid. if you don't believe the cd works just put aluminum foil over it and see if it makes a difference. the hard drive platter is very k00l, but it's overkill. fordem's metal lid is nicer than my can lid...no sharp edges.

hey this is homebrew...e x p e r i m e n t .

godsmoke · 08-10-2002

hmm ... it is possible that I'm making too much of a big deal out of this, but I want to make one just like the fab-corp, just not spend $60 -- I would rather spend 10 hours than $60.

I already took measurements and it turns out that the second part of the antenna (straight part) is 1/2 of a 802.11b wavelength. This is probably part of the design, so instead of going to mm measurement from the picture, go for 1/2 wavelength (61.4125mm)

I'm still looking for a ratio to match the bottom part -- and possibly the coil.

stay tuned...

sparafina · 08-10-2002

I used a disk platter because I was playing around with the stepper motor. It seems to work just fine, but I haven't really tried it out beyond a quick test drive, I'm more concerned with the dimensions of the radiating element.

fordem · 08-10-2002

Quote:

Originally posted by sparafina
the shiny stuff is a thin foil, that's why it's so much fun to micowave them.

I always thought that was some sort of lacquer - scratches pretty easily too.

sparafina · 08-11-2002

from http://www.howstuffworks.com/cd1.htm

"A CD is a fairly simple piece of plastic, about four one-hundredths (4/100) of an inch (1.2 mm) thick. Most of a CD consists of an injection-molded piece of clear polycarbonate plastic. During manufacturing, this plastic is impressed with microscopic bumps arranged as a single, continuous, extremely long spiral track of data. We'll return to the bumps in a moment. Once the clear piece of polycarbonate is formed, a thin, reflective aluminum layer is sputtered onto the disc, covering the bumps. Then a thin acrylic layer is sprayed over the aluminum to protect it. The label is then printed onto the acrylic."

08-10-2002	#1 (permalink)
godsmoke Student / Sys Admn. Join Date: Aug 2002 Location: NYC, USA Posts: 78	finally attempting to build one of the fab-corp antennas Hi all... Well, after some debating, I think I might attempt to build one of those 5 dbi magmounts. Thank you to outcast_one for posting pics of his magmount antenna. These pics can be found here: http://forums.netstumbler.com/showth...&threadid=2034 Anyway, after looking at suggestions, (since the second most important part of that antenna is the ground plate) I decided that I would use a hard drive plate. It took some looking for screwdrivers and busting a drill bit -- but I got one of the plates out, and plan to use it in my design. I'm going to be posting pics on my website (www.godsmoke.com/antenna.html) in about a week when I get the time to sit down and build the thing. Anyone know what kind of metal to use? Where might I get this metal? (for antenna post) Thank you for all your help... -godsmoke

08-10-2002	#10 (permalink)
lincomatic Squaaawk! WiFi! WiFi! Join Date: Apr 2002 Location: Tinsel Town Posts: 1,682	i think you are making too big a deal about the ground plane. i just used a tin can lid. if you don't believe the cd works just put aluminum foil over it and see if it makes a difference. the hard drive platter is very k00l, but it's overkill. fordem's metal lid is nicer than my can lid...no sharp edges. hey this is homebrew...e x p e r i m e n t . __________________ ~lincomatic

08-10-2002	#11 (permalink)
godsmoke Student / Sys Admn. Join Date: Aug 2002 Location: NYC, USA Posts: 78	hmm ... it is possible that I'm making too much of a big deal out of this, but I want to make one just like the fab-corp, just not spend $60 -- I would rather spend 10 hours than $60. I already took measurements and it turns out that the second part of the antenna (straight part) is 1/2 of a 802.11b wavelength. This is probably part of the design, so instead of going to mm measurement from the picture, go for 1/2 wavelength (61.4125mm) I'm still looking for a ratio to match the bottom part -- and possibly the coil. stay tuned... __________________ -godsmoke

08-11-2002	#14 (permalink)
sparafina Registered Member Join Date: May 2002 Location: TX,MD,NY Posts: 1,430	from http://www.howstuffworks.com/cd1.htm "A CD is a fairly simple piece of plastic, about four one-hundredths (4/100) of an inch (1.2 mm) thick. Most of a CD consists of an injection-molded piece of clear polycarbonate plastic. During manufacturing, this plastic is impressed with microscopic bumps arranged as a single, continuous, extremely long spiral track of data. We'll return to the bumps in a moment. Once the clear piece of polycarbonate is formed, a thin, reflective aluminum layer is sputtered onto the disc, covering the bumps. Then a thin acrylic layer is sprayed over the aluminum to protect it. The label is then printed onto the acrylic." Last edited by sparafina : 08-11-2002 at 12:11 AM.

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08-10-2002	#3 (permalink)
godsmoke Student / Sys Admn. Join Date: Aug 2002 Location: NYC, USA Posts: 78	Hi, yeah, you make a good point -- I have no idea about how it might work (well or not) -- thought it might be worth a shot. I got the idea from this website -- where someone has built a clone of the fab-corp http://www.geocities.com/lincomatic/homebrewant.html let me know about your ideas I think I'm gonna buy the fab-corp anyway...though I live in manhattan, NYC, so I don't think finding WAPs will be too hard. -godsmoke

08-10-2002	#5 (permalink)
sparafina Registered Member Join Date: May 2002 Location: TX,MD,NY Posts: 1,430	You can use wires (radiator+5%) as a groundplane arrayed around the antenna/radiator at 90 degrees. You could also use an old cd if you want. A car hood also works.

08-10-2002	#6 (permalink)
godsmoke Student / Sys Admn. Join Date: Aug 2002 Location: NYC, USA Posts: 78	hmm ... this sounds like it would work -- but I'm just wondering what you mean exactly, could you provide a diagram or picture? Would the hard drive plate work -- I already broke a bit and so forth to get a hard drive plate out. it's a good size... -godsmoke

08-10-2002	#9 (permalink)
godsmoke Student / Sys Admn. Join Date: Aug 2002 Location: NYC, USA Posts: 78	I would think so... Yeah, I mean if a hard drive doesn't work -- then I have no idea how a cd would work. it has to be accepting the radio signals which is something cds (plastic) do NOT do well... Anyway... Anyone every used a hard drive plate for a ground plane?? Success? Failure? Tell me how it turned out...

08-10-2002	#12 (permalink)
sparafina Registered Member Join Date: May 2002 Location: TX,MD,NY Posts: 1,430	I used a disk platter because I was playing around with the stepper motor. It seems to work just fine, but I haven't really tried it out beyond a quick test drive, I'm more concerned with the dimensions of the radiating element.