This lab for students is based on the article: Antenna on the Cheap (er, Chip) by Rob Flickenger, Jul. 05, 2001 05:20 PM available here: http://www.oreillynet.com/cs/weblog/view/wlg/448

Step 1: get parts and tools

Parts list:

1. All-thread, 5 5/8" long, 1/8" OD
   

2. two nylon lock nuts
   

3. five 1" washers, 1/8" ID
   

4. 6" aluminium tubing, 1/4" ID
   

5. A connector to match your radio pigtail (e.g. a female N connector)
   

6. 1 1/2" piece of 12 gauge solid copper wire (used house electrical wiring will do)
   

7. A tall Pringles can (any flavour, Ridges are optional.)
   

8. Scrap plastic disc, 3" across (or a second Pringles can lid)
   

Tools required:

1. Ruler
   

2. Scissors
   

3. Pipe cutter (or hacksaw or rotary tool, in a pinch)
   

4. Heavy duty cutters (or rotary again, to cut the all-thread)
   

5. Something sharp to pierce the plastic (like an awl or a drill bit)
   

6. Hot glue gun
   

7. Soldering Iron
   

Estimated construction time: about an hour

Step 2: Build front collector

Mark and cut four pieces of tubing, about 1.2" (1 15/64").

Where does this number come from?

First figure out the wavelength at the bottom of the frequency range we're using
(2.412 GHz, or channel 1). This will be the longest that the pipe should be:

  W = 3.0 * 10^8 * (1 / 2.412) * 10^-9

  W = (3.0 / 2.412) * 10^-1

  W = 0.124 Meters

  W = 4.88 inches

We'll be cutting the pipe to quarter wavelength, so:

  1/4 W = 4.88 / 4

  1/4 W = 1.22"

Now figure out what the shortest we'll ever use is (2.462 Ghz, or channel 11):

  W = 3.0 * 10^8 * (1 / 2.462) * 10^-9

  W = (3.0 / 2.462) * 10^-1

  W = 0.122 Meters

  W = 4.80 inches

  1/4 W = 1.20"

Practically speaking, what's the difference between the shortest pipe and the longest pipe length? about 0.02", or less than 1/32". That's probably about the size of the pipe cutter blade you're using. So, just shoot for 1.2", and you'll get it close enough.

Cut the all-thread to exactly 5 5/8". The washers we used are about 1/16" thick, so that should leave just enough room for the pipe, washers, and nuts.

Pierce a hole in the center of the Pringles can lid big enough for the all-thread to pass through. Now is probably a good time to start eating Pringles (we found it better for all concerned to just toss the things; Salt & Vinegar Pringles get to be almost caustic after the first fifteen or so.)

Cut a 3" plastic disc, just big enough to fit snugly inside the can. Use another Pringles lid, with the outer ridge trimmed off, to be ideal. Poke a hole in the center of it, and slip it over one of the lengths of pipe.

Step 3: Assemble the pipe

Nut Lid Washer Pipe Washer Pipe Washer Pipe-with-Plastic Washer Pipe Washer Nut

Tighten down the nuts to be snug, but don't over tighten (I bent the tubing on our first try; aluminium bends VERY easily.) Just get it snug. Congratulations, you now you have the front collector.

Eat the chips, wipe out the can, and measure 3 3/8" up from the bottom of the can. Cut a hole just big enough for the connector to pass through. This seems to be the "sweet spot" of the can.

On the Pringles Salt & Vinegar can, the N connector goes directly between Sodium and Protein.

Step 5: Build element

Use hot glue to hold the connector in place. If you have a connector that uses a compression nut and washer, and you're really careful about cutting the hole, you could use that instead.

Now, insert the collector assembly into the can, and close the lid. The inside end of the pipe should NOT touch the copper element; it should be just forward of it. If it touches, your all-thread is probably too long.

Now connect your pigtail, aim carefully, and have fun!

This concludes this lab