Home"brew" EVDO Antenna

Performance...on the cheap

It has been discussed before, but I thought I would give a step-by-step process on how to make this because it is so simple and works so well. I used a coffee can but you could pick up a shiny new paint can from Lowes or Home Depot and it would work just as well.

The victim:
The hole for the modem needs to be 1 to 1.5 inches from the back of the can for Sprint 1900 MHz and 2 to 3.4 inches for Verizon 800 MHz. due to the wavelength of each service:

Measure and mark where you are going to cut it and drill a few holes to get you started:
Cut out the hole and file down the sharp edges edges until it is large enough for the modem:Put some duct tape over the hole and cut it open with a razor blade:

Slide the modem into the slot. The duct tape helps give a snug fit and prevents the can from scratching it up:

Here I drilled a hole forward of the modem slot and fastened a quick-release plate for a camera tripod. You can use anything that will work for you to support it:

Assembly is complete. I attach a USB extension cable and mount it to the tripod:

All hooked up and ready to find a good quality signal:

If you have read my earlier posts then you have an idea where your tower is located. Just point it in that direction and make incremental changes in the x/y position to find the strongest signal with the least Ec/Io, a low packet error rate, and a Receive Signal Strength around 4-11 dB (higher is better).

This home-made antenna is known as a "circular waveguide" type.

A note is in order here:

Receive Signal Strength (RSS) differs from Receive Signal Strength Indicator (RSSI). It is a positive integer expressed in dB and is a ratio of the total power sent ... to the total power received, including noise. . RSSI is a negative integer expressed in -dBm and is a measurement of signal strength/power . It tells you nothing about the quality of that signal. Both of these measurements are often found in the debug screen of your modem. RSSI is the reading you get when the mouse cursor is placed over a certain spot on your connection manager or is clearly displayed. RSS is found only in the debug screen or other technical data/field test screen, not as a button on the connection manager.

A reasonable rule of thumb is: the closer to zero RSSI is... the stronger the signal, and the further from zero RSS is...the better the quality of that signal

If you have a different type of modem or want a quicker way of doing this you could just stand your modem up inside the can, keeping in mind the correct distance, and let the cable run out the front. No tripod? Put it on top of a step ladder or something similar and secure it with duct tape

This "home-brewed" antenna easily rivaled the performance of the panel antenna I bought and clearly outperformed the Omni that I have. A easy, cheap way to see if you can get a good signal before buying a commercial antenna. Money saved.