Showing posts with label am. Show all posts
Showing posts with label am. Show all posts
Friday, December 20, 2013
Two Transistor AM Transmitter
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 220pF capacitors used instead.
Circuit diagram:
Simple AM Transmitter Circuit Diagram
To tune it to a particular frequency, reduce one or both of the 220pF capacitors to raise the frequency or add capacitance in parallel to lower the frequency. Q1 is biased with a 1MO resistor to give a high input impedance and this allows the use of a crystal ear piece as a low cost microphone.
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Circuit diagram:
Simple AM Transmitter Circuit Diagram
To tune it to a particular frequency, reduce one or both of the 220pF capacitors to raise the frequency or add capacitance in parallel to lower the frequency. Q1 is biased with a 1MO resistor to give a high input impedance and this allows the use of a crystal ear piece as a low cost microphone.
Author: Peter Goodwin
Sunday, March 31, 2013
Use LA1800 Portable AM and FM Radio
This portable AM and FM radio circuit is designed using the LA1800 IC and some other external components. As you can see in this circuit diagram the LA1800 manufactured by Sanyo Semiconductors , require few additional components. The LA1800 am FM portable radio circuit needs to be powered from a 3 volt DC power supply circuit.
You can use an 3 volt battery. This radio receiver circuit has a low current dissipation of 5.6mA for FM band and 3.2mA for AM band .Also the output signal is driven into earphone speakers , but you can use an additional speaker ( in that case you need to connect an additional small power audio amplifier).
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