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End fed longwire or random wire antenna

Slim Jim Antenna

To view a few of my antennas and station, look at MY STATION

Warning about antenna models!

The dipole is the basic building block of many antennas. A dipole does NOT have 2.2 dB gain over an isotropic radiator when the dipole is placed over earth. The dipole has about 8.5 dB gain over an isotropic radiator! Always remember this when you see antenna models over earth given in dBi. If the model over earth shows a "gain" of about 8.5 dBi, the model effectively has the same gain as a dipole.

Here is the pattern of a 145-foot high copper wire dipole over medium real earth on EZNEC:

dipole gain in dBidipole gain dBi



You can see the gain is 8.5 dBi, and it is just a simple dipole just over 1/2 wave high. Any antenna you model should always be compared to a standard like this!

The notion a dipole has around 2.15 dBi gain is only true for freespace.







Multiple Articles at:

Receiving: Contains information in many articles. Receiving antennas including Beverages and Beverage Antenna Construction, Loops, K9AY, Pennant, Flag, EWE, Slinky Beverage Antennas, vertical arrays, magnetic loop antenna, and terminated loop arrays.

Transmitting:  Pictures of some transmitting antennas at my station. Most transmitting antennas link from the top of this page.

Single articles:

Balun and Core Selection: Contains information on core selection for transformers and baluns

Baluns, Sleeve balun: How they work

Baluns, transmitting: What they do, how they do it, and how to test them

Balun, Toroid: Winding style, debunking split-winding will improve performance  

Crossfire Phasing: Contains information on cross fire phasing and why it is superior for broad bandwidth arrays

Combiner and Splitters: Contains information on Magic-T splitters and combiners, how they work and what they do

Curtain Arrays: USIA and Distributed Feed Curtains, Sterba Curtains, Lazy H antennas and other curtain antennas

Detuning Towers: A quick explanation of how it works and the incorrect idea that you adjust for minimum current! Pass this along, it is a major error to tune for minimum current!

EH antenna: the E-H and CFA antennas. How they work. 

Inductors, Loading: A brief tutorial on loading inductors

Mobile and Loaded Antennas: Small loaded antenna systems

(Related page: Inductor spice model)

Short Antennas and feed line loss: Remember to include feed line losses in models  

Omega and Gamma Matching: Contains technical information on Omega and Gamma matches and matching, impedance limits, component selection, component failures  

Radiation and Fields:  What the terms we use actually describe

Radiation Resistance: A revised (as of Feb 14, 03) tutorial on radiation resistance and how it is used and misused 

Rohn Tower: How we installed various Rohn towers by lifting with a crane

Rohn 65G: How we built a gin pole or erection fixture for Rohn 65G, and the final result

Rhombic antennas: Models and theory of a rhombic antenna

Traps: Measurements and operation of traps and trap antennas. Including trap antenna loss.

since May 2004

2003,2004 W8JI