"Plastic Fantastic" Magnetic Loop- Linear actuator drive
"Plastic Fantastic" Magnetic Loop- Linear actuator drive Introduction I have constructed a linear actuator drive version of VK5JST's trombone capacitor tuned "Plastic Fantastic" magnetic loop antenna for 20 m. The linear actuator drive considerably simplifies the construction and waterproofing. The linear actuator was too fast at 10 mm/s. A 12V pulse width modulation (PWM) was used to slow it down to a usable speed. The SWR is dependent on the coupling between the drive loop and the main loop. While 1.1 is meant to be possible, I achieved 1.5 with some adjustment. Tuning the antenna while operating a SDR TRX is possible as the noise is visibly higher in a spectrum scope waterfall; Win4IcomSuite on IC-7300. The noise on the S meter rises from S2 to S6. . The design The antenna uses the underground plastic gas pipe now widely available, including Bunnings. The pipe has a PTFE inner, a layer of aluminium then an outer of yellow plastic. With the PTFE ...