Factual error: Hogan calls the radio detection truck "radar" when he orders the SS guard to switch it off. From other episodes, we know that Hogan knows what radar is, and back then, the difference between radio homing equipment and radar was even clearer to people than it is today, because radio homing was an established technology, while radar was brand new, and most people were not even aware it existed.
Factual error: Baker picks up a lot of static in his radio, then suddenly signs off and says "Sounds like the radio detection unit picked up our signal." Unlike radar, radio signal homing relies entirely on measuring the signals emitted by the transmitter that is tracked. It works by comparing the strength of the signal arriving at each component of an array of directional antennae. The process is completely passive and does not cause any alteration of the signal measurable at either receiver or transmitter at all, and certainly not any audible interference or humming.
Other mistake: The place the car ends up on the porch is where the wooden steps would have been. But there is no debris from the destroyed steps, meaning they were removed for the gag.
Other mistake: As the camera looks at the now-crashed car, the position and condition it is in is impossible. Though funny, there is no way the car could have jumped up on the porch as shown. The front would have been crushed in, the wood of the porch damaged. The interiors of the doors are impossible given that the car would have been kept in an immaculate condition.
Revealing mistake: As the camera looks at Schultz driving the car, even though he's moving in the seat, you can see through the back glass the car isn't moving at all.
Visible crew/equipment: As Schultz drives away from the boys, the camera crew and equipment is reflected in the window.
Answer: It's a solitary cell. Steve McQueen, star of 'The Great Escape' is known as the 'Cooler King'.