Adams’ RF Research

 

In a remote location within the Oregon Coast Range, electronics research into Radio Frequency phenomena, electrostatics, and solar power is performed at the Fortress of Solitude. Here the Age of Invention continues, inspired by the work of electrical engineer Nikola Tesla, mathematician Benoit Mandelbrot, physicist Hugh Everett, and author Kenneth Robeson, among others.

Artex Aircraft Supplies gave me complete freedom in the lab and this is what I came up with – one of the world’s first coupled-resonator dual-band portable antennas for Emergency Locating Beacons.

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The prototyping and testing was done in 2005 around the time that the ME406 ELT became available. Artex has gone through two acquisitions since then so my contribution has become an obscure factoid. Another idea I submitted for New Products became the company’s first project, a multi-output avionics power supply. Other NPI submissions I made included a universal passenger restraint system for cars, planes and helicopters, and a drown-proofing system for swimmers that used a small cartridge of buoyant gas, a water sensor and a timer that is fitted on a belt or vest. What happened to these ideas is a mystery. I submitted over 50 NPI projects to our Engineering Manager Mr. Noodlemeyer.

 

Kindle eBooks:

Secrets of Electronics Repair

 

 

Build Your Own DTV Super-Antenna

 

 

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The UHF-17 DTV Antenna

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Make Your Own Tri-Band DTV Antenna

 

 

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See J.D. Adams’ Author Central Page

 

The Adams-Yagi Antenna

The Yagi-Uda Antenna was invented in 1926 by Shintaro Uda and Hidetsugu Yagi of Tohoku Imperial University, Japan. In one of my new designs I’ve used the loop implementation of the Yagi dipole configuration to achieve high gain and a good impedance match across the UHF DTV band. The first ‘director’ loop also serves as an antenna element resulting in broader bandwidth and a 99.86 % efficiency. A series connection sums the impedances of the two loops with a half-wavelength section of 300 Ohm twinlead. The total gain approaches that of a conventional dual driven element antenna using a single element. Doubling the Adams-Yagi antenna structure to create a dual antenna design would yield a theoretical gain of 17.3 dBi at 650 MHz, an impressive figure for only 2 sets of directors. 

 

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UHF Gain at 650 MHz

 

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Standing Wave Ratio across the UHF DTV channels

 

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NEC Model showing grid reflector, driven square loop, driven ‘director’ loop, and a second director loop

 

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Using 300 Ohm twinlead with a Velocity Factor of .82, a physical length of 8.61 inches equals an electrical length of 10.5 inches for the phasing transmission line. The 300 Ohm input feedline can be any multiple of 10 inches for a flat response. The reflector is mounted 3.75 inches behind the primary driven antenna loop, and the first director is mounted 3.75 inches in front of the primary driven loop. The second director is mounted 11 inches in front of the primary loop. These spacings will focus the RF energy and maintain an acceptable impedance match to the 300 Ohm feed line. Despite the aspect ratio of the graphic, the driven loop is a square that is 7.5 inches on each side, the first director loop is 5.25 inches on each side, and the second director loop is 4 inches on each side. #10 or #12 gauge copper wire is used for best results.

JD Adams' Bio 

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