Showing posts with label am. Show all posts
Showing posts with label am. Show all posts
Tuesday, November 18, 2014
AM Portable Receiver Using ZN414
a AM portable radio receiver using ZN414 IC. The ZN414 ic has now been replaced by the MK484 which is identical in performance and pinout.
Designed around the popular ZN414 IC this receiver covers the range of medium wave band of approximately 550 to 1600 KHz with the values indicated. The condenser coil and tuning can be taken from an old MW radio to save time. The ZN414 IC, has been replaced by the MK484. The integrated circuit is a 3 pin, tuned circuit radio frequency, and incorporates several RF stages, automatic gain control and an AM detector. Its easy to overload and voltage of th IC is critical to success.
In this circuit a small voltage regulator turns on the transistor BC108B, 1N4148 diodes four, 2k7 and 10k resistor and the resistance of pre 820R. The 10k pot control acts as a receptor selectivity for all, control the operating voltage for the ZN414 (or MK484).
The audio amplifier is built on an investment of 741 op-amp amplifier circuit. Additional current pulse is provided by the BC109C / BC179 complementary pair of transistors to drive a 8 ohm speaker. The voltage gain full audio amplifier is around 15. The audio output of the complete receiver is really good and undistorted.
Designed around the popular ZN414 IC this receiver covers the range of medium wave band of approximately 550 to 1600 KHz with the values indicated. The condenser coil and tuning can be taken from an old MW radio to save time. The ZN414 IC, has been replaced by the MK484. The integrated circuit is a 3 pin, tuned circuit radio frequency, and incorporates several RF stages, automatic gain control and an AM detector. Its easy to overload and voltage of th IC is critical to success.
In this circuit a small voltage regulator turns on the transistor BC108B, 1N4148 diodes four, 2k7 and 10k resistor and the resistance of pre 820R. The 10k pot control acts as a receptor selectivity for all, control the operating voltage for the ZN414 (or MK484).
The audio amplifier is built on an investment of 741 op-amp amplifier circuit. Additional current pulse is provided by the BC109C / BC179 complementary pair of transistors to drive a 8 ohm speaker. The voltage gain full audio amplifier is around 15. The audio output of the complete receiver is really good and undistorted.
Sunday, September 7, 2014
Low Range AM Radio Transmitter Wiring diagram Schematic
Simple radio transmitter for transmission up to 25 metres. It is basically an AM modulator whose signal can be received on the normal AM radio. It can also be used as an AM radio tester.
IC 555 (IC1) is used as a free running multivibrator whose frequency is set above 540 kHz. Here the schema is designed for a frequency of around 600 kHz. The frequency of the multivibrator can be calculated as follows:
f=1.443(R1+2R2)C1
Low-Range AM Radio Transmitter Circuit Diagram
where resistors R1 and R2 are in ohms, capacitor C1 is in microfarads, and frequency f is in hertz. This frequency can be changed by simply replacing R2 with a variable resistor or C1 with gang capacitors. But it may increase the complexity of the schema. A condenser microphone is used for speaking.
The IC 555 multivibrator is used as a voltage-to-frequency converter. The output of the condenser microphone is given to pin 5 of IC1, which converts the input voltage or voice signal into its appropriate frequency at output pin 3. This frequency produces an electromagnetic wave, which can be detected by a nearby radio receiver, and you can hear your own voice in that radio. Note that the receiver should be AM type. If there is no noise in receiver, tune it to 600 kHz.
The schema operates off a 9V regulated power supply or a 9V battery. For antenna, connect 2-3m long wire at pin 3.
This schema costs around Rs 30.
Sourced By: EFY. Author name: Parag Purushottam Ingle
Friday, August 29, 2014
Powerful AM transmitter
The schema for a powerful AM transmitter using ceramic resonator/filter of 3.587 MHz is presented here. Resonators/filters of other frequencies such as 5.5 MHz, 7 MHz and 10.7 MHz may also be used.
Use of different frequency filters/resonators will involve corresponding variation in the value of inductor used in the tank schema of oscillator connected at the collector of transistor T1.
The AF input for modulation is inserted in series with emitter of transistor T1 (and resistor R4) using a transistor radio type audio driver transformer as shown in the schema. Modulated RF output is developed across the tank schema which can be tuned to resonance frequency of the filter/resonator with the help of gang condenser C7. The next two stages formed using low-noise RF transistors BF495 are, in fact, connected in parallel for amplification of modulated signal coupled from collector of transistor T1 to bases of transistors T2 and T3. The combined output from collectors of T2 and T3 is fed to antenna via 100pF capacitor C4.
The schema can be easily assembled on a general-purpose PCB. The range of the transmitter is expected to be one to two kilometers. The schema requires regulated 9-volt power supply for its operation. Note: Dotted lined indicates additional connection if a 3-pin filter is used in place.
Saturday, August 23, 2014
ZN414 Portable AM Receiver
Designed around the popular ZN414 ic this receiver covers the AM band from 550 - 1600 KHz with the values shown. For Longwave the coil needs to be changed. Use one from an old MW radio to save time. The ZN414 is a tuned radio frequency designed and incorporates several RF stages and an AM detector. It is easily overloaded and the operating voltage is critical to achieve good results.
The BC107 acts as a voltage follower, the four 1N4148 diodes providing a stable 2.4V supply. With the 10k pot , which acts as a selectivity control, and the b-e voltage drop of the BC107, the operating voltage for the ZN414 is variable from 0 to 1.8volts DC. If you live in an area that is permeated with strong radio signals, then the voltage will need to be decreased. I found optimum performance with a supply of around 1.2 volts.
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The audio amplifier is built around an inverting 741 op-amp. Extra current boost is provided using the BC109 / BC179 complementary transistor pair. The voltage gain of the complete audio amplifier is around 15. The audio output of the complete receiver is really quite good and free from distortion. I may provide some sound samples later.
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The BC107 acts as a voltage follower, the four 1N4148 diodes providing a stable 2.4V supply. With the 10k pot , which acts as a selectivity control, and the b-e voltage drop of the BC107, the operating voltage for the ZN414 is variable from 0 to 1.8volts DC. If you live in an area that is permeated with strong radio signals, then the voltage will need to be decreased. I found optimum performance with a supply of around 1.2 volts.
The audio amplifier is built around an inverting 741 op-amp. Extra current boost is provided using the BC109 / BC179 complementary transistor pair. The voltage gain of the complete audio amplifier is around 15. The audio output of the complete receiver is really quite good and free from distortion. I may provide some sound samples later.
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