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Showing posts with the label Medium

Medium Power Inverter Circuit Diagram

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In this Medium Power Inverter Circuit Diagram, a CMOS inverter, such as the CD4069, is used to convert the open drain Lx output to a signal suitable for driving the gate of an external P MOSFET. The MTP8P03 has a gate threshold voltage of 2.0 V to 4.5 V, so it will have a relatively high resistance if driven with only 5 V of gate drive. To increase the gate drive voltage, and thereby increase efficiency and power handling capability, the negative supply pin of the CMOS inverter is connected to the negative output, rather than to ground. Once the circuit is started, the P MOSFET gate drive swings from +5 V to -Vour· At start up, the -Vour is one Schottky diode drop above ground and the gate drive to the power MOSFET is slightly less than 5 V. Medium Power Inverter Circuit Diagram The output should be only lightly loaded to ensure start up, since the output power capability of the circuit is very low until -VoUT is a couple of vults. This circuit generates complementary output signals f...

Simple Medium Wave Modulator

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If you insist on using a valve radio and listening to medium-wave stations, you have a problem: the existing broadcasters have only a limited number of records. Here there’s only one remedy, which is to build your own medium-wave transmitter. After that, you can play your own CDs via the radio. The transmitter frequency is stabilised using a 976-kHz ceramic resonator taken from a TV remote control unit. Fine tuning is provided by the trimmer capacitor. If there’s another station in the background, which will probably be weak, you can tune it to a heterodyne null, such as 981 kHz. As an operator of a medium-wave transmitter, that’s your obligation with respect to the frequency allocations. And that’s despite the fact that the range of the transmitter is quite modest. The small ferrite coil in the transmitter couples directly into the ferrite rod antenna in the radio. Medium-Wave Modulator Circuit Diagram The modulator is designed as an emitter follower that modulates the supply voltage ...

Medium Wave Active Antenna

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This circuit is designed to amplify the input from a telescopic whip antenna. The preamplifier is designed to cover the medium waveband from about 550Khz to 1650Khz. The tuning voltage required is 1 to 12 volts and can be obtained from a 10k potentiometer connected to the 12 Volt power supply. Medium Wave Active Antenna Schematic RV1 is the gain control allowing weak signals to be amplified or strong signals to be attenuated. The control voltage is applied to gate 2 of TR1, a dual-gate MOSFET, the signal voltage applied via gate 1; the input signal being tuned via L1 and the two varicap diodes at the MOSFET's input and also by L2 and the varicaps at the MOSFET's drain terminal. Both tuned circuits provide high selectivity across the entire tuning range. To aid stability the MOSFET stage is fed from a stabilized supply consisting of ZD1 and R6. To drive low impedance (50 ohm) receivers, the medium output imepedance of the BF981 stage is enhanced by the composite amplifier made f...