Teacher kit · session 6
Build an antenna and measure it
60 minutes · Grades 9 to 12
Bring: wire; a tape measure; an SO-239 chassis mount; a NanoVNA or the club's SWR meter; the reachability page.
Goal
Students build a quarter-wave ground plane for 2 metres, measure it, and see the terrain check change when the antenna goes up.
Cut (20 minutes)
234 divided by the frequency in megahertz gives the radiator length in inches: 234 / 146 is about 19.2 inches. Four radials the same length, bent down at 45 degrees. Compare the arithmetic with the club's commercial antenna.
Measure (20 minutes)
Sweep with the NanoVNA or check SWR with the meter across the band. Trim in small steps. Write down before and after.
Reach (20 minutes)
Run the terrain check from the school to the nearest repeater with the handheld at desk height and again with the antenna at window height: the verdict is the same, the signal report from the volunteer on the repeater is not. Log a heard report from the school's grid square.