Tuesday, June 11, 2013

Double T Bar Verticals

Double T Bar Verticals

The 20M Vertical Double T antenna is designed to use available aluminum antenna tubing. This tubing can be shipped UPS in 6 foot sections. The T bars are made from 3/4" tubing and the vertical is made from sections of 1" tubing. The T Bars are 5 foot long. The vertical sections are 6 foot with a center section. The center section is made from 2 - 7 1/2" pieces of tubing with a 1" gap for the transmission line. The middle section are joined together by inserting a piece of 3/4" PVC sch. 40 plastic pipe. There is a little slop between the PVC and the tubing but is pretty snug. Use sheet metal screws to secure the tubing to the pipe.

Double T Bar Vertical antenna are vertical antenna with cross bars on the top and bottom. These crossbars provide capacitance loading thus reducing the size of the antenna. There are several companies that make them commercially. Force 12 and Transworld have reduced sized multi-band H vertical. Force 12 also make full half wave single band Double T Bar verticals. These commercial antenna are very portable and have been used on DX Expeditions.

This antenna is designed to be 2 feet off the ground. You can use a piece of 3/4" PVC Pipe to mount the antenna to a pipe inserted in the ground. Leave at least a 2" gap between the antenna and pipe (this is high resistance / high voltage point). The transmission line needs to lead away at a 45 degree angle. This will prevent the transmission line from interferring with the antenna.

20M Double Bar T - SWR Curves

20M Double Bar T - Elevation Plot

20M Double Bar T - 3D Plot

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