Editing Frequency modulation (section)

==Noise reduction==
FM provides improved [[signal-to-noise ratio]] (SNR), as compared for example with [[amplitude modulation|AM]]. Compared with an optimum AM scheme, FM typically has poorer SNR below a certain signal level called the noise threshold, but above a higher level – the full improvement or full quieting threshold – the SNR is much improved over AM. The improvement depends on modulation level and deviation. For typical voice communications channels, improvements are typically 5–15&nbsp;dB. FM broadcasting using wider deviation can achieve even greater improvements. Additional techniques, such as pre-emphasis of higher audio frequencies with corresponding de-emphasis in the receiver, are generally used to improve overall SNR in FM circuits. Since FM signals have constant amplitude, FM receivers normally have limiters that remove AM noise, further improving SNR.<ref>{{cite book |title=Reference Data for Radio Engineers |edition=Fifth |pages=21–11 |year=1970 |publisher=Howard W. Sams & Co. |editor=H. P. Westman}}</ref><ref>{{cite book |title=The ARRL Handbook for Radio Communications |publisher=American Radio Relay League |year=2010 |editor=H. Ward Silver |editor2=Mark J. Wilson|author=Alan Bloom |chapter=Chapter 8. Modulation |page=8.7 |isbn=978-0-87259-146-2}}</ref>