Monthly Archives: November 2018

Decibels: Pesky Little Critters In our telecommunication careers, we may have all used dBs in our work. Here is a little background and how we use them in amateur radio. Decibels are a form of mathematical shorthand using logarithms. Logarithms probably originated with the ancient Greeks. Logarithms have the property expressing large values or ratios in more easily understood human terms. Decibels originated when the engineering of analog telephone circuit became more complicated. The Bell System of fond memory in the 1920’s needed a way to design telephone circuits taking into account cable and component losses plus the gain of amplifiers. One […]

By Jim, N6TP, n6tp@arrl.net We are familiar with the formula for a half-wave dipole. It appears in the antenna handbooks and in various test questions for amateur radio license exams. It goes like this. Divide the operating frequency in MHz into “468” and the answer comes out in feet. For example: 468 divided by 7.150 MHz equals 65.5 feet! If we do a little rounding, we will cut our half-wave dipole to 65 feet 4 inches. Let’s look a half-wave dipole. As the name implies it is a half-wave antenna resonant at its operating frequency. We choose to make it a half-wave dipole as […]