If I want to use a different controller with my Bit Char-G of 45 MHz, I have to buy another car that uses the 45 MHz frequency and use its controller right? Or is it possible to change the chip on the car so that it uses a different frequency?
You can buy another controller and put the crystal from the one into the new one if you can't find a 45mhz controller. But I know of no way to change the frequency of the car itself.
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Sitting at my workbench in my comfortable little Hobbit Hole.
If you want to change the frequency of the car itself, the easiest, and probably cheapest route would be to snag a cheap clone to swap the PCB out of. Clones in the under 10 dollar range have become plentiful, and are great for parts.