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This rugged power supply is based on the popular LM338 3-pin voltage regulator. The LM338 is capable of supplying 5 A over an output voltage range of 1.2 V to 32 V with all standard protections like overload, thermal shutdown, over-current, internal limit, etc., built in. In this power supply, some extra protections have been added to make it particularly suitable for use with low to medium-power portable and mobile VHF/UHF (ham) and 27 MHz transceivers. Diodes D4 and D5 provide a discharge path for capacitors C1 and C2. Diode D8 protects the supply against reverse polarity being applied to the output terminals. Capacitor C1 assists in RF decoupling and also increases the ripple rejection from 60 dB to about 86 dB. If junction R1-R2 is not grounded by switch S1A, transistor T2 starts to conduct, causing the regulator to switch to zener diode D7 for its reference voltage (13 V). The PSU output voltage will then be 12.3 V. Normally, T2 will be off, however, and the PSU output voltage is ...

For those of you like / love to talk in the air can assemble this simple circuit that can be received by the radio receiver to within a few hundred feet. The voice that issues by this circuit at all clear without rustling. Can also be used to link communications over the air using this radio transmitter, provided that other person also had the same circuit. This PCB design : Description : Resistor R1__________________1K R2__________________18K R3__________________82K R4__________________1K2 R5__________________5K6 R6__________________39K R7__________________18K R8__________________68K R9__________________470R R10_________________100R R11_________________50K XTal Q1__________________ Crystal according to the desired frequency Inductor L1__________________10uH Capacitor C1__________________10uF C2__________________30uF C3__________________20uF C4__________________47uF Transistor Tr1_________________2SB175 Tr2_________________2SB175 Tr3_________________2SB178 Antenna X1-1________________...

This simple circuit is sure to have the police beating a path to your door- however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat. Simple Radio Wave Alarm Circuit Diagram : Notes : The circuit transmits on Medium Wave (this is the small problem with the police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates at just over 1MHz. This is modulated by an audio frequency (a continuous beep) produced by IC1b. When a hand or a foot approaches the sensor, the frequency of the transmitter (IC1a) drops appreciably. Suppose now that the circuit transmits at 1MHz. Suppose also that your radio is tuned to a frequency just below this. The 1MHz transmission will therefore not be heard by the radio. But bring a hand or a foot near to the sensor, and the transmitter's frequency will drop, and a beep will be heard from the radio. Attach the antenna to a multiplug adapter that is plugged into the mains, a...

SW Converter for Digital AM Car Radio Circuit Diagram This circuit is purposely presented with many loose ends (not literally, of course) to stimulate experimenting with RF circuitry at a small outlay. Looking at the circuit diagram you may recognize a modified version of the SW Converter for AM Radios described elsewhere in this issue. The modifications were necessary to make the circuit compatible with a digital rather than analogue AM car radio. The main difference between digital AM radios and their all-analogue predecessors is that tuning is in 9 kHz (some-times 4.5 kHz steps) in compliance with the international frequency allocation for the band. Obviously, that particular step size, desirable as it may be on MW, is a stumbling block if you want to use a digital AM receiver in combination with a frequency step-up converter for SW, where chaos reigns and there is no fixed step size. The first attempt was to make the crystal oscillator variable by about 5 kHz each way.   SW Co...

This device is reversal of a radio station , because it sends an empty signal to the frequency chosen in order to remove the actual broadcast. Removing broadcasting? Is the radio transmitter would be lost 10.000W , yes we only use this circuit at close range only , because the utility block radio station not far away . This device needs to close to the antenna radio receiver, at least according to the ammount of radio frequency ( RF ). To the circuit schematic can be see below.  Description : R1____39K R2____10K C1____0.001uF C2____10pF C3____10pF C4____22pF Q1____2N3563 L1____6 turns on ferrite core This is example coil winding : Ferrite diameter 5-8 mm Wire diameter 0.8 mm 6 turns on ferrite. How to use : After the circuit finshed and ready to use , then turn on the device , place tnear a radio receiver that you want. To adjust your signal live racing up and down winding on ferrite which have benen installed. After a suitable signal , the signal received by the radio receiver in ...

This simple hack turns your Raspberry Pi into a powerful FM transmitter! It has enough range to cover your home, DIY drive-in movie, a high school ball game, or even a bike parade (depending on the stragglers). PiFM software not only boldly enhances the capability of your Pi, but does so with nothing more than a single length of wire. This hack starts with the absolute minimum you need to run a Raspberry Pi — an SD card, a power source, and the board itself — and adds one piece of wire. It’s the coolest Pi device we’ve ever seen with so few materials. [ ]

Radio Control for toy car Play toy cars controlled by radio signals is an interesting game. The much-loved toy cars children, plus a simple circuit would be ideal for toy cars. This series of families use traditional digital CMOS IC which requires a very small electric current, so it does not impose on the performance of the original toy cars. In this system, radio signals emitted not continuously but only generated when the controller sends a command left / right or forward / backward, and even then only a radio frequency of an intermittent, so it is sending pulses of radio wave frequency. Number of pulses sent represents a command is sent, the command GO is represented by 8 pulses, represented by 16 pulses LEFT, RIGHT DOWN 32 pulses and 64 pulses. Command sent to a combination of two orders once gus, which is a combination of command forward / backward and right / left, for example, could be sent forward command and left once gus, in this case the number of pulses sent is 24, which i...

If you're in the market for a new auto sound system you might want to seriously take a moment and consider whether or not you would be benefited by subscribing to either Sirius or XM Satellite Radio. Both of these subscription-based services have something wonderful to offer their subscribers and both of them require specialized equipment in order to operate. This means if you are going to wish to use either service, you will need to have decided which service before you have your auto sound system installed. It really doesn't matter which of these you choose they each have different features that will appeal to a wide variety of audiences. You will find some wonderful competition among the two not only by way of music radio but also talk radio. If you really love talk radio you really need to subscribe to one of these in order to find a treasure chest of talk radio gems. You will find everything from the mundane to the controversial. From Oprah to Howard Stern exist in the rea...

Tuned Radio Frequency (TRF) Receiver Circuit diagram. Super heterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second world war other, simpler receiver technologies such as the TRF receiver and the regenerative receiver were still widespread. Tuned Radio Frequency (TRF) Receiver Circuit diagram :   Tuned Radio Frequency (TRF) Receiver Circuit Diagram The circuit described here is based on the old technology, but brought up-to-date a The most important part of the circuit is the input stage, where positive feedback is used to achieve good sensitivity and selectivity. The first stage is adjusted so that it is not quite at the point of oscillation. This increases the gain and the selectivity, giving a narrow bandwidth. To achieve this, the potentiometer connected to the drain of the FET must be adjusted very carefully: optimal performance of the receiver depends on its setting. In ideal condit...

Maybe you do not believe , because so long radios sold in the form usiong DC power as the driving component work. But I took to fiddling with radio without making a circuit of electrical current/voltage source which is rather strange. Radio Works well if no one put the components in accordance with its placement or its symbol. Therefore , we must consider the placement and and examined before starting step in assembling this very simple circuit. Description : R1=2K2 C1=Varco (variable capacitors ) 0-250 pF C2=100pF D1=Crystal Diode OA72 A = Receiver Antenna 10-20 meters along L1=Spool of wire antenna using nikelin / copper 0.25mm and 12.5mm koker and as 30 rolls wrapped arround to ferit. The circuit above is only useful as a radio receiver only. Can be called a crystal radio. The diode will process the sound waves through the antenna, then stored to capacitors.

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. AM and FM Radio with LA1800 Portable Project 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).