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Old 20-Jan-2012, 8:22 PM   #21
GroundUrMast
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Join Date: Oct 2010
Location: Greater Seattle Area
Posts: 4,773
Quote:
Originally Posted by sc2dave View Post
Sorry,all of these letters and numbers are 100% Greek to me.
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 ÁH (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.
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Last edited by GroundUrMast; 22-Jan-2012 at 6:05 AM. Reason: Added load coil dimension estimate
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