Data Sheet
-144-
387. FM Technology
Build the circuit to the left, turn on the switch (62) or press the press
switch (61) and you will hear some FM radio stations from the speaker
(93). You may have to press the press switch (61) connected to CH+ to
get the FM receiver to scan for a channel. For best FM reception, hold
the open end of the spring wire (9) in the air.
FM stands for Frequency Modulation, which means that the
instantaneous frequency deviation (dened as the difference between
the instantaneous frequency and carrier frequency of the radio signal)
is proportional to the voltage level of the audio signal. The FM receiver
collects the radio signal over the air through the spring wire (9),
demodulates it (eliminates the carrier frequency to provide a baseband
signal) and then uses a frequency detector to recover the audio signal.
388. FM Frequency Band
Build the circuit to the left, turn on the switch (62) and you will hear
some FM radio stations from the speaker (93). You may have to press
one of the press switches (61) to get the FM receiver to scan for a
channel. For best FM reception, hold the open end of the spring wire
(9) in the air. When you press one of the press switches (61), the FM
receiver scans for a radio station. In the FM band in the Americas, radio
stations range from 88 MHz to 108 MHz.