Possible can for cantenna

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Possible can for cantenna

Postby Starpoint » Tue Jul 20, 2004 5:58 pm

I know this will sound like a crazy idea.. but go to a supermarket and measure a can of soup from "Progresso" the cans have an inside diameter of 3 1/4 and a depth of 4 3/16

Now if you use any of the wave guide spreadsheets, you will see this can has the "PREMO" diameter for a freq response... 2.1 gig to 2.7 gig puttin the 2.4 gig that alot of the wifi stuff operates on right in the middle.

the can is 4 3/16 inches long so what one can do is get 3 cans, and CAREFULLY braze them together end to end, then trim it back to 10 inches, you get a length / guide wavelength of 1.015 which is means 1 full wavelength.

if you drop the length down to 9.875 (9 7/8ths length) the length / guide wavelength goes to 1.003 so the numbers get better.
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Postby Thorn » Tue Jul 20, 2004 6:17 pm

Starpoint wrote: ... is get 3 cans, and CAREFULLY braze them together end to end ...

For a quick test, get some 3M metal "auto body" tape and wrap the seams. It's fairly strong, comes in about a 25' roll, and is quicker than brazing. Most auto parts stores carry it.

Once you've got the optimum length, you can braze it for the permanent setup.
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Postby Starpoint » Tue Jul 20, 2004 6:28 pm

Was thinking the same thing... and having access to some Tig torches (used to work at a welding supply and brother still works there) can weld it as well..

I have a feeling there will be wardrivers going out to their local supermarkets with tape measures.

Oh.. and speaking of tape measures.... often times you need one that is both SAE and Metric (inches and MM)

I was at IKEA furniture.. and they had TONS of these plastic flexible (you can roll em up over a pencil) rulers that are 1 meter in length and is enumerated both SAE and Metric.

now the best part.. they had em hanging out on stands for FREE.. all you can grab.. so check out some of the big furniture stores or if you are lucky and have an IKEA in your city... snag a few.

also.. for antenna elements try using copper coated brazing rods from a welding supply.... they sell it by the pound in precut lengths of 3 feet.. figure about 1- 2 bux a pound but that will get you 20 rods... sometimes if you ask nicely, they will give you 1 3 footer for free.. and since most elements are maybe 1.5 inches tall or less... 3 feet give you alot of extra

Home Depot and Loews sell solid strand ground wire (12 guage) cheap.. I bought a 50 foot roll for about 3 buxs...
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Postby Eyecannon » Wed Jul 21, 2004 11:53 pm

I just use simple masking tape to connect the cans, doesn't seem like it would work that well, but it's held perfectly for over a year, and I haven't had to be delicate with it at all.

I've heard the optimal diameter is around 3.65", so those cans seem a little small. I've had great success with the standard 3.9" coffee cans.
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Postby Starpoint » Fri Jul 23, 2004 5:17 am

you might want to use one of the many waveguide calculators mentioned all over the forums..

using a can that has an 3.250 inch inside diameter (3 1/4 inch) and tube length of 9-7/8 inch long with the element placed 1.370 of an inch from the back at a height of 1.210 inch tall. Your freq response is 2128.388MHz to 2779.954MHz. The length / wave guide is at 1.003 ( going to a 10 inch tube length makes it 1.015) so yeah this will look like a pringles can more or less but it should give you the range (aka milage)
Against the run of the mill, static as it seems

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