Also beim Marantz ist ja auch so ein Knopp und hier kam schonmal die Frage auf:
"What does the FM Multipath function on my tuner or receiver do?
A: When an FM signal reaches your tuner or receiver, it is important that the signal is received directly from the station - think of it as looking right down a flashlight beam. FM signals can reflect, just like that flashlight, off of certain types of surfaces such as metal buildings and even geological rock formations. When this happens, the reflected portion of the signal has traveled a longer distance to reach your tuner or receiver, and this causes the phase of the sine waves that make up the signal to differ from that of the direct (non-reflected) signal.
Since the two types of signals are traveling over different paths, the term "multipath" was coined to describe this condition concisely.
The reflected signal mixes with the direct signal at the receiving antenna, and the combination of the two is what reaches your tuner or receiver. From basic algebra we know that when you add two identical waveforms that are out of phase with each other, you get a third, new signal with a new waveform shape - which, in the case of FM reception, means that you are receiving a signal that now contains a distorted representation of the audio component within it. That, of course, is not what we want to be listening to.
The FM Multipath options on tuners and receivers allow you to either hear, or see, the component of the signal that is out of phase. That, in turn, allows you to direct (turn or aim) your FM antenna so that the amount of reflected signal is as small as possible as compared to the direct signal. This results in the least possible distortion when your audio system presents the recovered FM audio to you.
In the case of a "listen-to" design, the button is usually a momentary push-button. This means you have to hold it in... it will spring back immediately when you release it. That is because the designers felt that you would not want to listen to the distorted (reflected) portion of the FM signal. It may also have been done, I believe, so that they would not get calls about the "audio being distorted" from customers that had somehow accidentally left the button depressed. It would be more useful if it stayed depressed, because some users have to cross the room to reach the controls that turn their antenna rotators, if indeed they have such gear (highly recommended, by the way!)
In the case of a "see" design, either a meter of some sort or an oscilloscope display is used. With meters, you simply adjust for the least amount of indicated signal. With a scope, various types of displays are used to detect the cleanest (most multipath-free) signal. For instance, on my 2130, the flatter the line on the scope is, the less multipath is affecting the signal.
Usually the designers of the tuner have allowed you the option to leave the oscilloscope or meter in the multipath measuring position, because simply viewing the multipath component doesn't affect what you hear at all."
Quelle:
http://www.classic-audio.com/marantz/mfaq.html
