February Ham Mobile Radio Setup

This forum is a continuation of the printed column "Q&A", where I answer questions about all aspects of electronics, including computer hardware, software, circuits, electronic theory, troubleshooting, and anything else of interest to the hobbyist. Feel free to participate with your questions, comments or suggestions on answers printed in the magazine. Send all NEW questions to: [email protected]
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February Ham Mobile Radio Setup

Post by G8RPI » Wed Jan 22, 2014 2:24 am

There is a problem with the ham radio power supply time switch.
You can't use a low-side (ground) switch for mobile radio equipment. The power ground load is nearly always common to the antenna ground and chassis ground (the only exception I know is some older British PYE commercial radios that isolated the internal circits from ground with capacitors). As the antenna (and chassis) is connected to the vehicle chassis ground, it will short-circuit Q2 and the radios will remain on. You need a high side switch or relay in the positive supply

Robert Atkinson G8RPI

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