Top Circuits Page 248
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A homebrew 2M transceiver I wanted to use it mobile so I wouldn`t have been able to use a fist mike. I had the bright idea of using one of those cheap personal hands free kits you can buy for mobile phones, however once installed reality struck home - hardly....
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Build a library of circuits and service data for old valve and transistor radios. There are many available on the internet, but at a price. I would rather share my circuits and manuals with others than try to make money out of them. Thanks to all those who....
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This scheme is an SWR meter, which is quite simple and easily built. Once you make a directional coupler, the results will be displayed with the measure led meters as a ratio SWR...
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Is based on the FTDI`s USB / serial IC FT-232BM. The adapter has been successfully tested with the following transceivers and software: VX-7R (VX-7R Commander), FT-8900 (FTB-8900), FT-817 (FT-817 Commander and Ham Radio Deluxe) and IC-706MkIIG (Ham Radio....
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Fortunately, Dodd`s 1909 receiver has survived. It was found among the many parts that were in various boxes that I had purchased at the yard sale. The pieces were identified from the 1909 Station photo. Many of the 1909 Station parts were used in the....
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Using SimPLL`s new PLL Wizard you can design a new PLL with a few clicks of the mouse. We have just designed one that tunes from 150MHz to 170MHz in 25kHz steps using a LMX2306 PLL IC and a MiniCircuits POS300 VCO. and because the LMX2306 and MiniCircuits....
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The main purpose is to show here the circuit diagram and explain the software. We use a UDP application to send commands to the microcontroller. Those commands will then cause the microcontroller to switch on or off the relay. It think it will be possible....
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This article celebrates in 2008 the 45 Years of the invention of PAL as well as to give an appriciation to the german television pioneer Prof. Dr. Eng. Walter Bruch, known as Papa PAL, Mister PAL or even among us collegues PAL pal . This document was first....
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This article by Arthur C. Miller was issued on page 88 to 90 in the book "Radio For The Millions" (prepared in 1945 by Popular Science Monthly staff, but first published in "Popular Scienece Monthly" April 1940). Fans who would like to install a radio on....
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The circuitry of the Regency shows some peculiarities. The circuit of the self-oscillating mixer stage, the base bias voltage of the second IF stage from the AF power stage, the unusual IF of 262KHz and the supply voltage of 22. 5 V are all characteristic of....
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The following is a translation of a section from the first book of the 3 part series "Die RG¶hre im UKW EmpfG¤ng" edited by Dr. Ing. Horst Rothe in 1952. This very interesting section describes a fully differential super-regenerative self-limiting FM....
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On the primary winding of the first IF transformer there is no capacitor. Does that mean it has only one tuned circuit, and the primary coil is just an inductive coupling The routing of the twisted pair couldn`t be done exactly the same every time. Was it....
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The schematic of its mixer part shows such an oscillator. The oscillator LC circuit only has two connections to the valve. It has no tap or tickler coil. Oscillations will only the occur, if the tube provides a negative resistance which compensates the....
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Original components, when still good, are stable and not subjected to infant mortality. Of course everybody has his own opinions derived from past experiences. Nevertheless answers may vary depending upon several reasons: quality of the design with proper....
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A radio that was stored for years on a dusty shelf must be awakened gently to return to its reliable operation and provide us with warm and pleasant sounds for years to come. Here are few generic notes on how a radio can be easily returned to life. Of....
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His oscillator sought to use resistors and capacitors instead of bulky low frequency LC tank circuits to generate audio frequencies. He obtained low distortion (<0. 5%) with the use of a two stage amplifier with enough negative feedback to set it`s gain to....
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Phase-sensitive detectors usually take the difference between an input FM signal and the same signal after it has passed through a resonant circuit, or through a delay line. A 1N34 should work fine to detect 100MHz, but not all 1N34 diodes are made alike.....
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The AVO VCM 163 is one of the few tube testers (British: valve tester) being able to measure tube electrode currents, e. g. plate and screen current (fig. 1, left-hand meter movement) as well as mutual conductance (fig. 1, right-hand meter movement)....
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Most models produced in the 30s rely on very similar circuits; in particular the RF section of most sets relies on the same LW-MW-SW scheme while the differences between different sets are based on the presence or absence of the variable selectivity control,....
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TR-55 was the first transistor radio produced and sold in Japan. It uses the following transistors: 2T51 (oscillator-mixer), 2 x 2T52 (for IF), 2T53 (AF driver) and 2T12. The very first commercially produced transistor radio was Regency TR-1 from October....
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Here are design data for a 3TF7 replacement. Design was based upon the information found in The Ballast Tube Handbook` by Jacobi and on the descriptive field of the R-390x part list: Actually, according to the voltage charts of R-390x receivers, the 3TF7....
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The following two photos show the I/V charactereristics of the main Anode/Cathode current for the Tune-a-lite 4 element neon tube used as signal strength meter in some Fada Radios as the Tune-o-graph. The 4 terminal Tuneon tube used in some Cossor radios....
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Feature of an offered frequency meter that he besides the main function allows to define inductance of various coils, resonant frequency of contours, capacity of condensers. The combined device which schematic diagram is shown on fig. 1 becomes the good....
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The block diagram explaining the device and operation of the sonic depth finder, is shown on fig. 1. The clock G1 generator operates interaction of knots of the device and provides its work in an automatic mode. Generated by it short (0, 1 c) rectangular....
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The lf555afosc1. pdf file download is the diagram (with notations) of Sub-Tone (CTCSS or "PL") Oscillator, made with the famous 555 timer IC set up for astable-multivibrator operation. The values shown place the tone range near the center of the standard....
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This circuit can be used for lighting a single (prototype) railroad signal. You could use this to drive a model railroad signal, but only if it is for a static display - for this circuit is not designed to be interfaced with anything. DCC systems, computers,....
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This is a great old periscope game. Ships pass by in the dark and your job is to hunt them down. When I plugged it in I heard a loud 60hz hum from the audio circuit. The game started but couldn`t aim properly and ships would not explode when hit. Also it....
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This JDM programmer works with a RS232, 9-pin(9 wire) DB9 Serial connector on your computer, and is used for loading Source Code (hex files) into your microcontroller. JDM programmers are Cheap and very easy to make. JDM programmer that we are going to make....
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This project demonstrates a computer control interface using a USB Board. (USB INTERFACE PROJECT). This tutorial will show you a simple way to control some device like led, motors and other devices with computer through a USB Board. The traditional way to....
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This is an amplified telephone line tap, which is designed to be minimally invasive. The interconnect to the phone line has a large input impedance, and is electrically isolated from the main electronics of the circuit. I designed this for use with a DTMF....
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The SSY-1 is a small pulsed Nd YAG laser originally used as part of the laser rangefinder in the M1 Abrams tank. The laser head and PFN-1 pulse forming network (flashlamp capacitor, inductor and diode) are readily available for under $250 as surplus on eBay....
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The SheevaPlug is reputed to have a marginal power supply. It seems to be more of an issue for the people in the UK running at 240VAC, and it also seems to be a problem to load the USB too heavily, as happens if you want to add an external mechanical disk....
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To the automatic transmission, there is a judder throught the box in fifth gear only and is more pro nounced when climbing an incline. If you knock it into sport mode and thus change down to fourth gear this judder disappears, it has been to the local ZF....
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Build a reprogrammable cartridge. Many things can be done with such a cartridge: You can develop your own applications or games and try them on real hardware instead of using an emulator. If you`d like to get into genesis development, I think the genesis....
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A few years ago, someone gave me a small wireless infra-red keyboard, part no. RC-KB2, designed to be used with a Kenwood audio system. As soon as I saw it, I wanted to discover it`s transmission format. Why Because I would then be able to build a small....
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This small PCB, which I named Multiuse tiny1 was originally designed to convert NES/SNES controllers to USB. Since there is not a lot of space availabe inside an SNES controller, I designed the PCB to be as small as necessary. The PCB has improved since the....
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This projects makes it possible to use Sega Saturn peripherals (controllers, mouse) on a PC through an USB port. Using the schematic and firmware available on this page, one can make an adapter (Using the connector from a Saturn extension) or convert a....
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Controlling room lighting using computer. I bought some triacs and opto couplers to do this. I drew the schematic and built a prototype. Everything worked well. We cannot see it on the pictures, but there is a cable going out of the box that plugs in the PC....
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The Flash-based program memory is where the program sketch is stored after an upload. The SRAM act as the main memory where program variables are temporarily stored as the sketch executes. The system clock synchronizes the internal operation of the CPU and....
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The idea is that the infra-red light is reflected by the disc, except by the dark red line. The reflected light is received by the sensor and this way the Arduino can keep track of the number of revolutions. Note that the infra-red sensor is sensitive to a....
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By testing many different circuits, I ended up with the simplest ( in terms of parts count and straight signal flow) design, similar to those " Heathkits", with one tone control and FET buffer. From modern features - only True By-Pass switching, DC jack and....
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The Sovtek 5881s that come in these amps are cheap and sound like it. Change ALL tubes. Get a Sovtek GZ34, Valve Art or GT KT66s, and Ei Gold preamp tubes. Rebias the KT66s to around 40ma at idle. Do not get Sovtek or "Golden Dragon" KT66s, as these are not....
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The most glaring ommision was that the DRUID did not accept confirm codes (ie the solution to the clue) and did not give directions to the next cluesite. Instead teams had to call in and confirm with Game Control in order to find out their next destination.....
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The 12F629/675 PICs are small 8 pin DIP devices that are ideal for our applications. They include and internal oscillator, a comparator, an analog/digital converter and timers. The Microchip PICkit1 is an ideal USB programmer. PicBasic Pro (PBP) is an easy....
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A very useful switch that can be controlled from any channel on the typical Futaba or JR radio set up. The switch was designed to trigger the shutter on digital cameras without the encumbrance of a servo glued onto the camera. However, apart from aerial....
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The problem is how to control the speed of the motor. One way is to use the plane, radio, and speed control with the motor in it. That`s no fun! Mount the motor on the bench and just plug the batteryinto the motor. That`s even worse! It`s hard on the motor....
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The Clearcom type intercom bus runs at a significantly lower level than the Sony bus, the signal to the camera operator`s headset must be boosted and the signal from the camera operator`s microphone must be attenuated. To do this a very small circuit board....
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A very simple controller circuit, with fairly smart performance! Can`t afford a fully automatic computer controlled rotator, but would like more capability from your basic rotator Would you like a simple to use "point and shoot" computer controlled antenna....
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This is designed to be used as a programmable LED display for numerous applications. I also wanted to include some additional features so that the display can be used instantly. The display uses a sure 8 x 32 LED dot matrix. This is interfaced to a Xino (or....
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For a couple of recent projects we have been asked to provide interesting and informative display units. We decided to build a unit which can be used in a number of different applications. It was designed to look good, be able to show graphics and text, have....
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We cover the hardware and the software and give a full design for a 12/24V DC 20A charge controller which can be used for solar, wind, hydro or pedal power applications. Please start here to get a full overview of the project. We have been wanting to design,....
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The amp has been designed to be an ideal upgrade for builders wishing to step up from Gainclones. This amp will kick out the power where Gainclones fall over, yet still maintain a sweet sound. The use of n-channel MOSFETs in the output makes the amp easy to....
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a magnetic pickup from an old record player can make a great pressure, and vibration sensor. replace the needle with a plate of thin metal (copper off a pcb is good, ) and you`ve got an incredible touch sensor. use this circuit to amplify the circuit before....
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This project is best suited for use as a sensor on a robot. This circuit will actually allow you to measure distances from an object. It measures in a `unit` and it`s range is about 10 inches. As the receiver and transmitter, you will use an ultrasonic....
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You can cut away the 555 timer oscillator part and add your favorite microphone modulating circuit to transmit voice over to your tv set with a little tuning. Schematics in Schematics Depot were found on the internet and assumed to be in public domain.....
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This schematic is a tone transmitter. For sufficiently small values of the resistor, it outputs a tone, so having a resistive mic (carbon mic) in parallel with or in place of the resistor. would modulate the tone frequency with the voice. I`m not sure how....
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The circuit described generates (transmits) ultrasonic sound of frequency between 40 and 50 kHz. As with any other remote control system this cirucit comprises of a mini transmitter and a receiver circuit. Transmitter generates ultrasonic sound and the....
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This is about as close as you can get to a real vintage Pultec EQP-1a. Built from the original Pulse Techniques Pultec schematic with the layout designed around modern replacement parts (filter caps and trannys); and utilizing best practices regarding lead....
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The mixer features two stereo phono inputs and two stereo line-level inputs and has one stereo mixing channel. A microphone input and a stereo main output with adjustable gain are also provided. General Circuit diagram : all passive circuitry (controls,....