Jan 26, 2007

Make your own external cell phone antenna.

If you aren't interested to spend a couple of hundred dollars for an external cell phone antenna then this is a must for you. Robert had made an ultra-cheap external cell phone antenna from coax cable and a h?nger which had worked for him.

Make your own external cell phone antenna (11) 1You'll need the following materials:

* A wire pants h?nger
* A length of coax cable (2' should do)
* A plug that fits into your phone's external antenna jack on your phone.

You'll need the following tools:

* A cutting tool for cutting the h?nger wire
* A drill for the cardboard portion of the h?nger
* A ruler with 1/16" increments
* A soldering iron and solder
* A pen / pencil


Construction
# Disassemble the h?nger.
The wire will be used for the antenna elements and the cardboard tube will be used mount the elements.

# Cut the following lengths of wire (except the DE at this time) and label them:

* R = 3 1/8"
* DE = 2 7/8" (remember, don't cut this one yet)
* D1= 2 13/16"
* D2 = 2 3/4"
* D3 = 2 3/4"
* D4 = 2 11/16"
* D5 = 2 5/8"
* D6 = 2 5/8"
* D7 = 2 9/16"

The piece DE (aka Driven Element for you Antenna designers out there) is going to be"J" shaped. The length of the top half will be 2 7/8" and the bottom half will be 1 7/16" and the distance between the top and bottom will be 1/2".

Make your own external cell phone antenna (11) 2
Make your own external cell phone antenna (11) 3# Mark the cardboard tube:
Along each side of the cardboard tube, draw two lines running the length of the cardboard tube. Make them roughly opposite ends of the tube from each other. The spacing isn't critical, this will just help make the elements come out in a parallel plane.

Mark the following spots from one end of the cardboard tube on each of the lines drawn previously.

* R = 1/2 "
* DE = 1 11/16"
* D1 = 2 7/16"
* D2 = 3 3/8"
* D3 = 5"
* D4 = 6 11/16"
* D5 = 9 3/16"
* D6 = 11 11/16"
* D7 = 14 5/16"

# Drill holes in the cardboard tube.
At each of the marks on both sides of the cardboard tube. The tube is hollow, so be careful to go through only one side at a time.

# Insert the elements into their respective holes.

# Prepare the coax cable.
There are usually five layers to coax cables. The outer plastic cover, a braided set of wires. Under the braided wires is a tin-foil thick covering of metal. This covers a thick plastic section with a thick copper wire in the center. If you are using a spare cable with coax connectors on both ends, cut one end off.

Carefully cut away the outer plastic cover about 3/4" from the end of the coax of an end of the coax cable with no connector.

Make your own external cell phone antenna (11) 4Separate the wires that are showing and gather them on one side. Unwrap the metal and gather it with the separated wires and twist the whole thing together.

Make your own external cell phone antenna (11) 5Cut through the thick plastic center being careful not to cut the center wire.

Make your own external cell phone antenna (11) 6# Attach the coax cable to the cardboard tube. Put the end you just prepared near the DE element and tape it in place. This will help with soldering.

# Solder the coax to the driven element. Just put one at the center of the top and the other just below it.

# Attach the coax cable to the phone
If you didn't buy a plug, you will want to fabricate a plug of some sort. If you're lucky, you have a phone where it's obvious where the leads go, but some have a plug with multiple leads and you would have to do some research to find which ones to use.

Tuning
This is a directional antenna, so you'll have to figure out which direction works best. If you're not sure, pick a random direction and wait 10-15 seconds to see if a better signal is registered. Generally a phone may take about 30-45 seconds to get to 4 bars. If you don't see any results, turn 45 degrees and wait again. Odds are, you should be able to figure out the optimal direction in just a couple minutes.

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