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AM Radio Circuits |
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AM radio began with the first, experimental broadcast on Christmas Eve of 1906 by Canadian experimenter Reginald Fessenden, and was used for small-scale voice and music broadcasts up until World War I. AM radio technology is simpler than Frequency Modulated (FM) radio, Digital Audio Broadcast (DAB), Satellite Radio or HD (digital) Radio. An AM receiver detects amplitude variations in the radio waves at a particular frequency. It then amplifies changes in the signal voltage to drive a loudspeaker or earphones.
The earliest crystal radio receivers used a crystal diode detector with no amplification. Medium-wave and short-wave radio signals act differently during daytime and nighttime. During the day, AM signals travel by groundwave, diffracting around the curve of the earth over a distance up to a few hundred miles (or kilometers) from the signal transmitter.
However, after sunset, changes in the ionosphere cause AM signals to travel by skywave, enabling AM radio stations to be heard much farther from their point of origin than is normal during the day. This phenomenon can be easily observed by scanning an AM radio dial at night. As a result, many broadcast stations are required as a condition of license to reduce their broadcasting power significantly (or use directional antennas) after sunset, or even to suspend broadcasting entirely during nighttime hours.
Because of its susceptibility to atmospheric and electrical interference, AM broadcasting now attracts mainly talk radio and news programming, while music radio and public radio mostly shifted to FM broadcasting in the late 1970s. However, in the late 1960s and 1970s, top 40 rock and roll stations in the US and Canada such as WABC and CHUM transmitted highly processed and extended audio to 11 kHz, successfully attracting huge audiences. Early experiments with stereo AM radio involved two separate stations (both AM or sometimes one AM and one FM) broadcasting the left and right audio channels.
This system was not very practical, as it required the listener to use two separate radios. Synchronization was problematic, often resulting in "ping-pong" effects between the two channels. Reception was also likely to be different between the two stations, and many listeners used mismatching models of receivers.
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After we published the original Li`l 7 AM Transmitter plans, fellow experimenter Scott Todd sent us information about his design for a similar portable, battery-powered transmitter. -Original Message- From: Scott Todd Sent: Wednesday, April 12, 2000 8:58 AM To: Walter Heskes Subject: A-1 minicaster I noticed that you have yet to get around .The antenna amplifier circuit has a part count of about 40, using the following active parts: 2 NPN transistors (BC548`s), 1 MOSFET (BF981), 2 Varicap diodes (KV1235), as well as a 6v2 zener-diode. there is and a 330uH (micro Henry) inductor / coil, which can be modified for operation on other frequency bands. Designed to work with a telescopic wh .The AM Transmitter circuits in two and a half, audio amplifier and an RF oscillator. The oscillator is built around Q1 and associated components. Tank circuit L1 and VC1 is melodious from about 500kHz to 1600KHz. These components can be used from an old MW radio, if available. Needs Q1 regenerative feedback to oscillate and this is achieved by con .This is a circuit diagram circuit AM portable radio receiver made from the ZN414 IC. The ZN414 ic has now been replaced by the MK484 which is identical in performance and pinout. Designed popular ZN414 IC this receiver covers medium wave band band from approximately 550-1600 KHz with the values shown. The coil and tuning capacitor can be taken fro .Here the AM Radio receiver circuit diagram based on old single IC MK484. Components part list: R9, R10_ 6R8 R6_ 100R R3_ 1K R1_ 4K7 R7_ 5K6 R4_ 10K R2_ 100K R5_ 150K R8_ 820K Pot_ 10K log pot Coil & ferrite bar set C7_ 470p ceramic C, C4, C5, C6_ 470nF monoblock C2_ 100nF. This circuit is a tuned radio frequency (TRF) receiver of the standard AM .The following diagram is the schematic diagram of 4 transistors FM transmitter circuit designed by Paul K. Sherby. Components List: R1, R2, R8 = 1K R3 = 100K R4 = 150K R5, R7 = 10K R6 = 220 ohm R9 = 10 ohm P1 = 5K trimpot D1 = 1N4002 Q1, Q2 = 2N3904 Q3, Q4 = 7001, NTE123AP C1. Here the SW transmitter circuit based on IC BEL1895. This particular... .This is the simple design and sensitivity and selectivity of the receiver are good. This circuit is use a compact three transistor, regenerative receiver with fixed feedback. The circuit is based on transistor as core of the operation. The transistor that is used is BC549. This is the figure of the circuit. The tuned circuit is designed for medium .Using TEA5551T monolithic integrated radio circuit can be designed a AM radio receiver circuit which is designed for use as a portable radio receiver with headphones. The TEA5551T radio receiver circuit contains all is needed for a AM radio receiver circuit (a complete AM part and dual AF amplifier with low quiescent current). Because in most cas .In this project, you will make a simple 3-stage low-power broadcast-type circuit, using a crystal oscillator integrated circuit and an a collector modulated AM oscillator with amplifier. You can connect the circuit to the an electred microphone or amplified dynamic microphone. Using an electred microphone is shown (in gray) in the diagram below.... .AM radio built around 555 timer chip. The only active device (silicon, germanium, or otherwise) is the LM555. The tuning is accomplished with an inductor and a capacitor, and the LM555 acts as an AM demodulator and class-D power amplifier to drive the speaker. You may be wondering how all this is accomplished with a 555. Here`s how the circuit wor .A power supply circuit to bring 24VAC down to 5VDC. I have an L7805CV, but rectified (a bridge) and smoothed (a 33 F electrolytic), the input is still $40V_{peak}$, which is more than the max input voltage the regulator can take. Looking at the regulator`s datasheet, it suggests the following "High Input Voltage Circuit", which notes "$V_{in} =... .Using ceramic tuning 3. 587 mhz resonator and resonator filters are also sold with a value of 5. 5mhz, 7. 7 mhz and 10. 7 mhz. Distance transmitter range is approximately 2-4km. the working principle of this circuit are filter resonator/ceramic filtersraise the frequency of the value of the resonator filter. This frequency is amplified by the... .Externally, the chassis looks identical to the 22BD. Exception: the 22BD has the jack for the speaker connection - two female sockets - on the right (antenna) side of the chassis; the 3BTD has a 3" harness (Black and Green wires) exiting the left side (same side as the power leads) and is a combined male/female connector. .The circuit of AM transmitter is designed to transmit (amplitude modulated) DSB (double side band) signals. A modulated AM signal consists of a carrier and two symetrically spaced side bands. The two side bands have the same amplitude and carry the same information. In fact, the carrier itself coveys or carries no information. In a 100% modulated .There are not many AM transmitters that are easier to build than this one because the inductor is not tapped and has a single winding. There is no need to wind the inductor as it is a readily available RF choke (eg, Jaycar Cat LF-1536). To make the circuit as small as possible, the conventional tuning capacitor has been dispensed with and fixed 22 .Given favourable radio wave propagation, the shortwave and radio amateur band are chock-a-block with SSB (single-sideband) transmissions, which no matter what language they`re in, will fail to produce intelligible speech on an AM radio. SSB is transmitted without a carrier wave. To demodulate an SSB signal (i. e. turn it into intelligible speech) i .This circuit shows an active antenna that can be used for AM, FM, and shortwave (SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. This circuit is designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios. L1 can be selected for the application. A 470uH coi .Here is the circuit diagram of a simple AM transmitter circuit that can transmit your audios to your backyard. This circuit is designed with limited power output to match the FCC regulations and still produces enough amplitude modulation of voice in the medium wave band to satisfy your personal needs. You will love this!. The circuit has two parts, .In this circuit, a 74HC14 hex Schmitt trigger inverter is used as a square wave oscillator to drive a small signal transistor in a class C amplifier configuration. The oscillator frequency can be either fixed by a crystal or made adjustable (VFO) with a capacitor/resistor combination. A 100pF capacitor is used in place of the crystal for VFO... .In previous article about how to make a radio we have discussed a simple crystal radio receiver circuit. The schematic mentioned here is also a simple AM radio circuit but it is not using a crystal, it is using high gain preamplifier stage of transistor BC 549. The circuit is using only few components to make a good quality am receiver. For makin .
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