Sorry about that, I offer the modeling software code for any who may be interested in it. I hope the attached graphics may be helpful in visualizing the changes to the radiation/receiving pattern as the antenna geometry is changed.

For those interested, 4NEC2 can be downloaded free of charge. http://home.ict.nl/~arivoors/Home.htm The software makes the job of designing a workable antenna within the reach of those of us who lack a masters or doctorate degree in mathematics and electrical engineering.

In the last 'code' post, the dimensions of a 5/8 wave whip is about 1.87meters (SY DEL=1.868521 'Element Section Length in Meters). A loading coil is needed as well, located at the base of the antenna, it's calculated value is about 0.6 µH (SY COIL=6.125e-7 'Load Inductance, Henrys). This should be enough information to build an experimental 5/8 wave vertical antenna for use in the FM broadcast band. (Using the calculator at http://www.daycounter.com/Calculator...lculator.phtml I estimate a coil 0.5" in diameter, 0.7" long and having 3 turns, will be very close to the needed value for the load coil.)

The modeling suggests that you would see about 2 or 3 dB better gain compared to a stock whip antenna.

do you ow if a bi-quad antenna can be used for a cell phone? I get terrible reception. One like this; http://www.ebay.com/itm/BIQUAD-ANTEN...item2eb543aace i know i need the connections

Theoretically, the fundamental idea is workable... but like an any other mobile radio, you'll usually want an antenna that's omnidirectional. The bi-quad you've linked to is a uni-directional antenna and if the cosmetics are any indication, I'm not impressed with the build quality. It's also advertized as a Wi-Fi band antenna (WiFi is dominantly in the 2.4 GHz range, whereas cell phone and PCS services fall in the range of 700 MHz to 2.3 GHz).

Finally, very few cell phones provide a means of disconnecting the original antenna... How would you connect an accessory/third party antenna?

There are 2 ports under the battery cover. 1 is labeled as "g" and the other is "r". The phone is a Samsung Admire.I thought of connecting to one of these.

Having downloaded the user manual for the Samsung Admire™, I can find no provision for attaching an external antenna. My guess is that g stands for green and r stands for red. My best guess is that those ports are intended for stereo earphones or speakers.

No,it already has a port for that on top of the phone.you have to take the battery cover off to even see them.

That is not the issue. The issue is whether or not the ports are antenna ports or ports with some other purpose. Are those ports antenna ports?

Not sure what the ports are.they sure are tiny.

The takeaway message is that they are not antenna ports and cannot be used as such.

biquad for cell phone
 

The short answer is Yes (but not that one)
This site is old ( first I ever heard about nec modeling software and before 802.11 g came out)
Scroll to the bottom of the page. http://trevormarshall.com/biquad.htm

If this is to be a mobile cellphone antenna then bi-quad is to directional.
Modern cell phones don't have a visible antenna so the "coupling" would be the main issue.
If the antenna is for a house you could arrange for your ez-chair to to be at the focus of an offset parabola (in the attic).
GroundUrMast is right about the construction of the biquad you linked to (copper clad pc board is terrible for this application) ,after 3 attempts using the printed circuit board I switched to copper flashing. (find a friendly siding installation crew to bend the lips on their brake )