T9A02

ANTENNAS AND FEED LINES · Antennas: vertical and horizontal polarization, concept of antenna gain, definition and types of beam antennas, antenna loading, common portable and mobile antennas, relationships between resonant length and frequency, dipole pattern

T9A02T9A →

Which of the following describes a type of antenna loading?

AElectrically lengthening by inserting inductors in radiating elements
BInserting a resistor in the radiating portion of the antenna to make it resonant
CInstalling a spring in the base of a mobile vertical antenna to make it more flexible
DStrengthening the radiating elements of a beam antenna to better resist wind damage

Why Antenna loading means adding reactance, usually a coil, to make a physically short antenna behave electrically like a longer, resonant one. A quarter-wave vertical on 40 meters would be about 33 feet tall, so a mobile whip a few feet long is made resonant by inserting an inductor (a loading coil) at the base, middle or top. The coil cancels the capacitive reactance of the too-short element so the feedpoint looks resistive at the operating frequency.

Watch out A resistor would not tune anything out; it would just waste transmitter power as heat, and a base spring or beefed-up elements are mechanical fixes, not electrical loading.

Loading = coil, not mechanical. Short whip plus inductor equals electrically full size.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

T9A02

The rest of T9A