You ’ve probably hear about AM radio and FM wireless , VHF and UHFtelevision , citizens band radio , shortwave radio and so on . Have you ever wondered what all of those different names really mean ? What ’s the difference between them ?
A radio wave is an electromagnetic wave propagated by an antenna . wireless waves have unlike frequencies , and by tuning aradio receiverto a specific frequency you could foot up a specific signaling .
In the United States , the FCC ( Federal Communications Commission ) decides who is able to employ which frequencies for which purpose , and it issues license to stations for specific frequencies .
When you mind to a radio post and the announcer tell , " You are listening to 91.5 FM WRKX The Rock ! , " what the announcer means is that you are mind to a radio station broadcasting a frequency modulate ( FM ) radio signal at a absolute frequency of 91.5 Mc , with FCC - assign call missive of WRKX . Megahertz signify " million of cycles per second , " so " 91.5 megahertz " imply that the sender at the radio station is oscillating at a relative frequency of 91,500,000 round per second . Your FM radio can tune in to that specific relative frequency and give you absolved reception of that post . All FM radio Stations of the Cross transmit in a band of frequencies between 88 megahertz and 108 megahertz . This band of the radiocommunication spectrum is used for no other purpose but FM radio broadcast .
In the same fashion , amplitude modulated ( AM ) radio receiver is confined to a banding from 535 kilohertz to 1,700 kilohertz ( kilo mean " thousands , " so 535,000 to 1,700,000 cycles per second ) . So an AM receiving set station that enounce , " This is AM 680 WPTF " mean that the radio station is send an AM radio signal at 680 kHz and its FCC - assigned call letter are WPTF .
On the next varlet , learn more about about frequency band and the frequencies that common gadgets use .
Radio Frequency List
mutual radio frequency band admit the following :
What is funny is that every wireless technology you could imagine has its own little dance orchestra . There are century of them ! For example :
Why is AM radio in a band at 550 kilohertz to 1,700 kilohertz , while FM radio is in a band at 88 to 108 Mc ? It is all completely arbitrary , and a lot of it has to do with history .
AM radio has been around a set foresightful than FM radio . The first radio broadcasts occurred in 1906 or so , and frequency apportioning for AM radio receiver go on during the 1920s . ( The harbinger to the FCC was establish by Congress in 1927 . ) In the 1920s , radio and electronic capabilities were fairly limited , hence the relatively low frequencies for AM radio .
Televisionstations were pretty much non - existing until 1946 or so , which is when the FCC apportion commercial programme bands for tv set . By 1949 , a million people owned television receiver sets , and by 1951 there were 10 million tv set in America .
FM radio was invented by Edwin Armstrong so as to make eminent - faithfulness ( and atmospheric static - free ) music broadcasting possible . He built the first station in 1939 , but FM did not become really popular until the 1960s . Hence the high-pitched frequencies for FM radio .
Radio Frequency Scanners
Most radios that you see in your casual life-time are unmarried - purpose wireless . For example , an AM radio can heed to any AM tuner station in the frequency band from 535 kilohertz to 1.7 megahertz , but nothing else . An FM radio can listen to any FM radiocommunication station in the band from 88 to 108 megahertz and nothing else . ACB radiocan listen to the 40 channel devoted to citizens set radio and nothing else . scanner are different .
Scannersare wireless receivers that have highly wide frequency vagabond so you could listen to all kinds of radio signals . Typically , scanner are used to tune in to police , ardour andemergency radioin the local region ( so electronic scanner are often call " police scanners " ) , but you’re able to use a electronic scanner to heed to all variety of conversations . Generally , you will either :
to expend a scanner , it ’s ideal to have estimable absolute frequency tables so you love where the action is . For more data , check out the connectedness on the next page .
