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cocoaNEC - Antenna Analysis Program for a MAC

The program cocoaNEC is a Antenna Analysis program for the MAC. It is written by W7AY a retired programmer for Apple. This is a freeware program that is great. It has some great features that are hard to abtain in some of the commercial programs. You have to enter the antenna by wire segments. It can be entered in several measurement systems, and by clicking on a different type measurement it will automatically convert it. I used cocoaNEC to analysis a 2M 3 Element Yagi. See Screens Shots below.

Describe Antenna by Wires

Enter each element in X, Y, Z oordinates. Then enter the radius of the element (it can be in # AWG if wire). Then the segments for calculations, the Driven Element should have an odd number if the coax it put in the middle.

The elements was entered in English -Mixed 1' 6"changing to Metric will change it to Meters.

Select a Ground for Calculations

Select the Driven Element and place the Source

Frequency Entry for all calculations.

Azimuth trace for the different frequencies. The outside ring ('0' dB) is 12.72 dBi. The Front/Back is about 18dB.

Elevation trace is for an elevation of 5, it will change if the height changes.

SWR trace is a Smith Chart. The center of the chart is 50 ohms resistive, if the dot is not on the line then it will have a re-active componet. The two grey rings are for SWR of 2:1 and 3:1. If it is inside the first grey circle then it will be less than 2:1. You can determine the number if you like from the Summary data (see screen shot below).

The Summary page has the Azimuth & Elevation traces and also give some of the calculated values.

The Geometry page is an indication of the Antenna. You can change the Elevation and Azimuth angles to change how the antenna is displayed. The colors indicate the current distribution.

This is a 3D plot of the antenna. This plot is great compared to other 3D plots.

You can get this program at the following address: http://homepage.mac.com/chen/w7ay/cocoaNEC/index.html If this is a bad address do a search for cocoaNEC or W7AY.