What Is Mirror Radio
About Mirror Radio
March 27, 2013 / Radio / Total 988 words / No Comments / onlookers 28 views + is now available in the market are generally superheterodyne radio Radio . Wherein ” heterodyne ” refers to the radio system . Direct addition to the formula , the formula digital processing (DSP), digital ( digital signal receiving station ) and the like.
Electronic technology has such a principle: to enter two different frequencies ( such as frequency 1 , frequency 2 ) in the same amplifier inside , will produce the following: In addition to the frequency of a frequency of 2 itself, but also a new generation frequency plus after two frequency frequency frequency frequency frequency 2 1 after subtracting the like .
Superheterodyne radio receiver principle as follows (in the FM band as an example) :
Generating an adjustment in the radio frequency, i.e., the “local frequency “into the amplifier. Meanwhile, from the antenna sensed ” radio frequency” is also sent to the same amplifier , it ‘s the next one or the next few stage amplifier frequency of only 10.7 trillion (radio frequency ) to zoom in, put on a lot of other frequencies is small . (This is the radio selective “)
Adjust the ” local frequency ” ( ie tuning process ) , when transferred to ” local frequency ” minus the ” radio frequency” ( ie, a frequency difference , so called ” super-heterodyne ” ) equal to the radio frequency 10.7 trillion , the Radio this signal has a maximum amount of amplification , ( ie, the frequency of the received radio ) .
Different frequencies, amplification of the amplifier is not the same, so to be converted into a fixed frequency, to ensure that the different radio stations on the same frequency selective amplification amount and improve the radio. By the way, the IF amplifier 10.7 trillion resonance curve “width” also affects the sound quality, it is more narrow , selective better, stronger anti-interference ability , but the sound quality is declining. Conversely sound better, worse selectivity. Important to note here: transform only the carrier frequency radio signals on the frequency of the “bearer” of broadcast content has not changed.
As mentioned above, into two different frequencies in the same amplifier inside , when transferred to the ” local frequency ” minus the ” radio frequency” radio frequency equal to 10.7 trillion , the largest radio this signal has put a lot of , received stations. However , in accordance with the principle said earlier , when transferred to the ” local frequency ” with ” Radio Frequency” is equivalent to 10.7 trillion radio frequency when in this position will receive the same radio station , the radio station is called mirroring . Its location is: actual radio frequency twice the frequency position subtracted or added after the IF frequency radio.
For example , radio frequency : 107.8 trillion = -2 * 10.7 86.4 trillion ( image frequency ) .
Radio Frequency: 87 +2 * 10.7 trillion = 108.4 (image frequency).
Careful users will find that in the range of 87 trillion FM frequency of -108 required, will not be mirrored stations. If you are receiving range -108 76 trillion, that is set to be able to close the campus radio , you may receive the mirror.
These are the circumstances FM band. In the AM band, due to the IF frequency is relatively low, the reception range is wide, mirror on the radio more, but the relevant state departments in the radio frequency settings will take this into consideration in order to prevent interference mirror .
repost by Fmuser