# Question about EVDO hack from 3x05

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Hi All,

I was watching through some old episodes, and I discovered this gem of a hack. I for the life of me cannot find documentation for this and the website for the guy who did the hack does not work. I have been to some EVDO forums and all I get is reviews for pre-built antennas and since I like trying it myself I would like to build one myself. Basically my project involves an HTC Mogul, which has an external antenna port in the back and I would like to make an antenna for road trips so I can get better signal to stream my music in the car. A google search for what was mentioned in the episode, "single pole element antenna", brings up mostly patent information about it and no information as to where to buy one or even start looking for one. Any help would be greatly appreciated!

-A

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Wasn't there a forumula that tells you how long to make the antenna for specific frequencies? I would google for antenna length per frequency or something to that effect. cut "monopole antenna" or dipole antenna lengths. I think power output can also change the formula, so a normal 18foot antenna can be shrunk down to like 18 inches with the same results. Something about distributed capacitance reducing the size and need for larger antennas.

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• 1 month later...

Geocities, nice :).

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Geocities, nice :).

generally it is considered that the speed of light(in Mps) divided by the frequency(in Hz) (in english is 300 divided by the frequency in Mhz) gives you the wavelength of the frequency.

1/4 of that wavelength is the frequency at which an antenna becomes resonant (give or take a little bit due to thickness of wires and surrounding cables etc) and another 1/4 wave is needed to balance the antenna for grounding. This is a basic dipole with basically no gain but can be a very effective antenna. the output of this would be in Metric not feet and inches....

so as an example 900Mhz..

300/900 = 33.33Cm wavelength

33.33/4 = 8.3325Cm for a 1/4 wave (main element)

and 8.3325Cm for ground

making the antenna 8.3325*2 = 16.6625Cm long

this antenna could be made from wire soldered straight to coax....

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