Antina

Its fun and easy to make your own antenna!

The prototype antenna I have used for some time has really worked well for me. Even though it was 7 inches long it still fit in my pocket and it allowed me to make calls where I wasnt getting service before. I really liked my antenna and I plan to use custom antennas on all the phones I own from now on. Please read through the entire directions so that you consider all the design needs of your custom antenna before you build.
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Practical Antenna Knowledge

Warez site ...
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Mating to a Treo 600 and a Treo 650

Physically mounting an antenna to the body of a treo is not an easy thing to do. The body of the treo is rounded and has buttons on the sides. On the prototype antenna I made for a Treo 600 I used a cut down aluminum case. Some people suggested modifying the antenna nub to hold the antenna. One idea to a mount to a Treo 650 would be to epoxy the antenna to the battery cover. Most people suggest adapting the case you own to fit an antenna. However you decide to mount it, the antenna must be built to withstand the perils of every day use. You must decide how to mount it, and if you want it to make it temporary or not.

backtreo1.jpg

The Treo's use a male FME connector out the back of the phone, near the base of the antenna nub. It allows us to bypass the built in antenna. A female FME connector is easially and cheaply found on ebay (keywords: treo antenna) or a specialty electronics store. They should be adapted to a coaxial cable, or already come with a cable. The cable can be be cut to lenth and stripped easially for our purpose.
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Choose the Type of Antenna

Im going to cover 2 types of antennas, Sprint (1900 MHz) and Verizon (800 MHz), although truthfully there are other CDMA carriers. Just determine the operaing frequency, ask your local carrier rep. CDMA will operating on one of these to freq bands. GSM folks can use some of the measurements found in the Multiband GSM page. I have had one GSM user say that his carrier uses only one freq, and if thats the case then by all means try it. You can adapt these plans to any freq with an online frequency calculator found at http://www.csgnetwork.com/antennagenericfreqlencalc.html
These numbers reflect actual center frequencies: CDMA

* Sprint 1900 band = 1850-1990 MHz = 1920 MHz center freq = 1.4625" 1/4h

* Verizon 800 band = 824-849 MHz = 836.5 MHz center freq = 3.568" 1/4h

GSM

* GSM 850 (USA) band = 824 - 849 MHz (uplink) and 869 - 894 MHz (downlink). Center freq = 859 MHz = 3.26" 1/4h

* GSM 1900(USA) band = 1850 - 1910 MHz (uplink) and 1930 - 1990 MHz (downlink). Center freq = 1920 = 1.4625" 1/4h

Please note that Sprint 1900 and GSM 1900 use the same freq range. Also note that this range has a much wider bandwidth than the other fequencies.


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UPDATE: Bridging Dipoles = BAD

The bridge, or the leads coming out of the coaxial cable going to the poles, are used to adjust the phase relationship of the 2 signals by electrically distancing the poles. As we saw in the "SPY" Antenna page 2 signals 180 degrees out of phaze could be measured against each other to make a much larger signal. Because in a dipole we are connected to the top of one pole and the bottom of the other pole placed end to end, making the antenna pyhsically rotated 180 degrees from each other. By having a bridge of 1/8h (1/4 total) we are 90 degrees back in phaze. This greatly reduces the effectiveness of the antenna. We want the bridge to be less than 1/8 wavelenth, at best we want it to be exactly nil. Make your leads, but keep them as short as possible! The wiki has been updated to reflect this.
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Sprint 1900/GSM 1900 Dipole

sprint_antenna.GIF

As you can see 1/4 wavelenth for 1900 MHz is 1.47 inches, the lenth you cut each pole. Try to keep your leads as short as you can!

The pic will be updated.
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Verizon 800 Dipole

verizon_antenna.GIF

As you can see 1/4 wavelenth for the 800 MHz band is 3.57 inches, the lenth you cut each pole. Try to keep your leads as short as you can!

The pic will be updated.
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Build the Poles

The poles can be made out of any conductor, but my first choice would be sturdy solid core wire or coat hanger wire for durability. Also the thicker the wire the more inductive properties it has, which is good (upto a point) for reducing the impedance of the antenna. Any wire can be used though.
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Cutting and Stripping the Cable

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The cable should be cut long enough to go where the antenna needs to be plus the amount that you need to solder the cable to the antenna. The outside insulation should be stripped back just enough to make your connections The wire shield needs to be pulled off the center insulation and seperated, and then made into a wire by straighting and insulating it with tape. Keep as much of the center insulation on the center conductor as long as you can, and only strip that insulation back far enough to make a connection. The center conductor is very fragile. You are now ready to attach the poles.
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Building the Dipole Antenna

Simply solder the center conductor to one pole, and the shield to the other. You will need to insulate the poles from each other, so use as much or as little electrical tape to satisfy this requirement. The poles should be arranged end to end and kept in a straight line. You will need to worry about protecting the antenna's solder joints, so attach the antenna to the mount of your choice as you see fit. The diagrams show the use of a "chock block," or a screw based wire terminator block, to both mount the poles securely and use a solder free connection. This is not a bad route to go, in fact you can simply epoxy the "chock block to the battery cover and be a great way to mount your antenna.
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Mount Your Antenna to the Phone

Sorry to be soo vauge, but there are lots of ways to do this. You must use your own creativity and engineering skills. Plus every user has different preferences and design needs. The digrams suggest attaching (temporarily or perminately) a "choc block" to the back of your phone. I cut up an aluminum case to make a clip mount and used ball point pen casings to house the antenna and keep it safe (and keep it from poking me!!!) You could use your belt clip mount or any type of case, feel free to experiment.
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Test the Antenna

Now that it is built, test it. The phone is quite safe, the worst possible senario is that the 2 poles somehow got grounded together, shunting all your signal to ground. In this condition the recieved signal would be lost and your transmitter would run at a miniscule 0.6 MW trying to find a cell tower. Other possible failures would include a broken solder joint or conductor, also giving you very little signal. I once even connected a call on my trusty treo 600 with no antenna at all! If you notice a big drop in signal or a sharp reduction in voice quality there could be something wrong, so stop using the antenna untill you figgure it out. If your RSSI drops only slightly with the antenna attached, like by 10 or so, this is normal and is only a fluctuation caused by the different resonance of the antenna. Only you can decide if this new antenna will be a part of your phone.