I've got a couple of TNC's and radio's in my car that I like to operate with backup battery after the car's ignition goes off. I use a charging circuit to keep the battery charged when the car is running.
This is my problem: when I start the engine, the ignition noise causes havoc with the TNC and other digital devices. I have tried chokes, filter caps etc. But the spikes are too broad. I tried a timed delay circuit for delayed switchover, but this causes too much complexity. I tried using a diode so devices can run on the filtered battery voltage while charging from the mains, but the voltage drop prevents proper charging. I am considering using a PWRGate to smooth that transition i.e., when starting the car and switching from battery to car's mains but not sure if it will provide a smooth enough transition. Any other ideas on how I can make this work? Michael K3MH Bellevue, WA
