The Many Different Types Of Interference: Knowing Is Half The Battle.
Author: Tymon Hytem-5496
Source: articledashboard.com
Apart from noise, other forms of interference found in radio receivers, as the image frequency, transmitters operating on an adjacent channel and transmitters operating in the same channel. Frequency modulation provides not only improved the sound to noise ratio, but greater discrimination against all other interfering signals, regardless of its source. As we know the frequency modulation with maximum deviation of about 75 kHz pre-emphasis provides noise rejection of at least 23 dB better than amplitude modulation. Therefore, if an amplitude modulation receiver noise needs 60 dB of sound on the enemy excellent detector performance, then an FM receiver will be the same for the noise performance of only 37 dB sound. These results, whether the interference signal is due to noise or adjacent channel signal. The mechanism of frequency modulation limiter to reduce the interference is exactly the same whether it is noise or adjacent channel signal. Moreover, each modulation frequency channel occupies 200 kHz transmission. Beyond this, only 180 kHz is actually used, while the remaining 20 kHz are the guard band to reduce adjacent channel interference more. The range limiter used in the frequency modulation receiver passes the signal stronger, but removes the weakest. It is for this reason that the noise reduction is obtained in the frequency modulation, provided the signal is at least twice the peak amplitude of noise. For the same reason, the relatively weak signal interference from any other transmitter operating in the same frequency as desired, would be diminished. The co-channel interference is suppressed in the frequency modulation. The possibility of co-channel interference arises in practice, when a mobile receiver moves from one transmitter to another operation on the same frequency. Interesting phenomena of the catch is done. Thus, frequency modulation, as the mobile receiver from a transmitter to the second, the second transmitter is inaudible practically do not interfere if the voltage signal from the transmitter second is less than half of those from the beginning. Beyond this point the second transmitter become very audible in the background and, finally, what is excluded dominated the first transmitter. Thus, the mobile receiver is captured by the second transmitter. When the receiver is in the transition region is approximately in the center and discoloration occurs, then the signal of the two transmitters are stronger alternative. Thus, the receiver is captured alternatively by a transmitter and then the other. This change from a transmitter to another is most annoying, not unlike the system of amplitude modulation. In amplitude modulation effect of receiver capture can not be obtained. In this case the mobile receiver moves from one transmitter provided predetermining while the other sounds like a very significant interference, although it can be difficult.