Is the external antenna of the car platform in the trunk not better than the center of the car

The car radio itself does not have an antenna, and an external antenna is required to receive the transmitted signal. Everyone knows that the antenna is best placed in the center of the car roof, but due to the unbalanced appearance and other actual conditions, many people finally choose the car trunk as the installation position. So, is the effect of installing the antenna in the trunk worse than installing it on the roof?
There are four important indicators for the antenna of the car: maximum withstand power, center frequency, bandwidth, and standing wave ratio.
We know that the car has a working range. We often say that the 400M low section (400-420), the high section (450-470), and the amateur section (430-440) are the same. Beyond this range, the receiving and receiving indicators of the car (mainly receiving sensitivity and transmitting power) will drop sharply or even fail.
The same is true for the antenna. We call the frequency of the perfect resonance of the antenna as its center frequency. At this time, the standing wave ratio = 1, that is, all the power transmitted by the vehicle is converted into electromagnetic wave radiation by the antenna. The VSWR is gradually increased when leaving the center frequency. When we increase the VSWR to 1.5 (the reflected power is 5%), the bandwidth is called the operating bandwidth of the antenna. When the standing wave ratio is greater than 1.5, it is not recommended to work. If it is greater than 2, it will definitely not work. If it is greater than 2.5, it will not work. Otherwise, the car will be finished. (Of course, the car also has protection circuit, but it is dangerous and cannot guarantee safety.)
The vehicle antenna needs to use the iron of the roof as a ground net to form an antenna system. Although the suction cup is insulated from the iron sheet, there is no small capacitance between the two, which is a path at a high frequency. Changing the position of the antenna actually changes the ground network of the antenna system, and the standing wave ratio will change.
In theory, the antenna should be placed in the middle of the roof. The ground network around this place is ideal, and it is also the default position for the antenna test. However, the fact that the seedlings are too long in actual life may affect the lower basement, so some friends put the suction cup on the trunk or use the card edge. At this time, if you want to make the working effect of the antenna reach the ideal state, you can use the standing wave meter or directly use the antenna tester. Select the position of the antenna while measuring, and ensure that the standing wave ratio is less than 1.5, you can put it outside the roof. Anywhere.