Hooking the counterpoise to the back of the radio is fine if the antenna is directly mounted to the RF connector on the radio. If the antenna is remote from the radio, even if it’s only 5 feet away, this will alter the length of the counterpoise. Let’s say you are operating on 10 meters. The actual counterpoise wire is cut for 6’ 8”. If you mount your antenna away from the radio and use 15 feet of coax to reach the antenna, your counterpoise will be altered by 15’. Your remotely mounted antenna will act like mono pole. Your vertical will be half of the antenna and the RF is looking for the other half of the antenna. Now your coax will become the other half of the antenna. If you mount your antenna remote from the radio, than the counterpoise must be place where the antenna is located. Adding a clip on ferrite on the antenna end of the coax is important. It’s not a dipole hung in the air, but it still needs a balun.