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This antenna project  consists of designing antennas using 4nec2 antenna simulator as a design aid and the construction/testing of a 10m dipole, a 50 Ohm 1:1 Balun and a 50 Ohm Line Isolator. The antenna design phase of the project is based on using 4nec2 antenna simulator using Microsoft Windows. There are many simulators that are free and most of them are based on a very old program that uses Fortran (NEC from the Lawrence Livermore Lab). Download the file from the 4nec2 link above and install it on your laptop computer. If you do not have a reasonable laptop computer, don’t worry as you will paired with a group member who can help you.  See the Antenna page for details on the use of 4nec2 and our objectives.   You will also construct and test a 10 m dipole that can be used either in portable applications or as a more permanent base station antenna.                 The Balun portion of the project consists of building and testing  a 50 Ohm 1:1 choke type Balun that covers    the frequency range from 1.8 to 54 MHz with a continuous power rating of 100 W. It uses UHF connectors, RG316 coaxial cable and a FT140-43 ferrite Toroid. The line Isolator to be constructed is very similar to the Balun except that it contains two UHF connectors so it can be inserted at the output of your transceiver. It has  similar performance of the Balun with a SWR close to 1.1 up the 54 MHz.  The Common Mode impedance is greater than 1000 Ohm over the complete band and much higher in the common HF range from 80 to 10 m.
Balun Under test from 1 to 54 MHz with a 50 Ohm load and an AIM 4170 vector impedance meter.  SWR  approximately 1.15 at 54 MHz due to the long leads from the RG316 center conductor to its outer conductor through the load and wing nuts. Balun prototype. SWR approximately 1.15 at 54 MHz. Balun Toroid:  11 Turns RG316 ( 730 mm long) wound counter-clockwise.   Short end 35 mm long held in place with a tie wrap.  Long end also held with a tie wrap.   The short end is connected to the UHF connector and the long end is connected to the solder connector on the stiffener plate. Assembly of the Isolator end cap.  Two vices are handy for doing this so the RG-316 does not get bent and possibly broken.  If you only have one vice, an assistant will be required while the RG-316 is soldered into the connector.
Isolator Toroid RG316-11 Turns, 890 mm long. Wind six turns, then cross under and wind five more turns. This allows the input/output portions to be placed on opposite sides of the Toroid.
Below are some photos of the Balun and Isolator during the building phase of the project.  There is more detail given on the assembly page.
Balun Toroid RG-316:11 Turns, 770 mm long. Short end (35 mm long measured from the outside of the Toroid) is connected to the UHF connector. Start and finish of cable secured with tie wraps.
35mm RG-316 11 Turns FT140-43 Ferrite