Chicken and Egg. If you can modify the radio (hardware/software), you can modify the protection device.
Adding a protection device merely shifts the problem (being discussed) from the radio to the protection device.
It achieves exactly nothing.
Adding a protection device merely shifts the problem (being discussed) from the radio to the protection device.
It achieves exactly nothing.
An example of the former is "homemade AM radio", where you wrap a lot of wire in a coil, and changing where you complete the the circuit along the coil allows you to "tune into" different frequencies.
An example of the latter is the cantenna, a directional antenna that can be made from a Pringles can.