Top Circuits Page 247
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This Hartley oscillator was built on the remains of a single tube Hartley using a single 45. The original circuit I constructed was one that was published in a 1932 QST article by George Grammer. As it turned out, both of the 45s I had were weak, so the....
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This project was inspired by a series of QST articles by Hayward, W1PH. I based my rig on his April 1962 article, "Have You Tried 160 Lately ". I liked his simple, single band rig. I thought his use of 6V6 tubes, along with regulated voltages, to be a simple....
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The inverter chops the 12 Volt DC Battery voltage into a square wave voltage of 50 cycles per second and duty cycle of 25%, transformed by transformer Tr1 to 230 Volt rms. IC1 forms the oscillator with 100 cycles per second (120 cycles per second for 60....
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The gap between TTL graves and the PC can be perfectly filled with modern microcontrollers. They not only contain the CPU but also program and data memory, EEPROM, I/O ports, timers, some even ADC and UART. With that you have a complete little computer....
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This circuit can be used from low frequencies to at least 120MHz using series resonant crystals on their fundamental or overtone mode. The output can be taken from the feedback tap as shown, a low impedance winding on L2 or from the drain of the J310 via a....
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For digital modes the ideal receiver must be very simple, front end selectivity, manually adjustable gain, IF filter. All the goodies you can find on the HF receivers can be done by software. In my junk box there were one surplus 1. 4 MHz, 3 kHz wide Xtal....
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Output transformer core: coming from flea market, light blue color, marked as A-438281-2-9H9-3, OD = 47 mm, ID = 24 mm, height = 13 mm. No information about µ Mosfet to be used: coming from flea market, with the following characteristics. It`s an obsolete....
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This simple PC parallel port ADC has 12 b resolution, four differential input channels and is it`s quite fast; the chip itself ( MAX186 ) is able to go up to 133 ksamples/s, but the actual speed will be determined by the software used. I wrote a simple C....
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A copy from an old italian magazine of amatorial electronics, proposing an add-on for tube receivers. The add-on was a simple one-tube short-wave transmitter leveraging the same power supply already available in the receiver. This circuit fascinated me when....
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Direct Digital Synthesis (DDS) frequency generation has been around for quite a while, but most of the homebrew DDS projects are rather complex and use expensive chipsets. Murray ’s exciter has only 3 inexpensive IC ’s,and the whole thing can be built for....
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Basic Regen design is pretty common, so BEFORE the schematic comes the "concept stage", the "what`s available in the junkbox stage", back to the "concept stage", followed by the "mechanical/electrical layout stage", then sketch a rough schematic. and do it....
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Back cover removed showing the power supplies upper deck and the original Dayton 2C915A (220vac - 140cfm blower) mounted to the underside of the cabinet. The RF deck enclosure was removed. Upper deck of the power supply with the original blower removed. From....
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The following is a layout of my repeater system and what was needed to get it on the air. The ILink system was designed by Graeme, M0CSH, and I take no credit for its success. The circuit below is only required by repeater control stations (sysops) and not....
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This page describes a modification that you plug in to your radio and computer. Do this at your own risk! It`s your choice to do this. I`m not forcing it on you. If you don`t, hey, no hard feelings, but if you do and mess something up, don`t blame me. This....
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When using an analog meter to set the output of a power supply used for testing 12-volt equipment, an expanded voltmeter scale has a decided advantage and accuracy over a linear scale. Figure 1 shows the original meter scale and the expanded scale used in....
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Boards are powered by two 9volt alkaline batteries. Circuits are a compilation of circuits found in the Radio Shack Engineering Handbook for making pulse modulated LED transmitters and receivers. The laser diode "D1" is substituted with an inexpensive laser....
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The schematic for the crystal bandpass filter/amplifier board appears below (left) withimages of the assembled and boxed unit appearing below center andright. The signal frequency bandpass filter isconstructed over a ground plane and housed in its own....
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This little project arose from a desire to experiment with some of the more "traditional" methods of radioconstruction which enjoyed popularity some 70 years ago. I wanted to find out for myself what kind of performance could be achieved using simple....
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The frequency of a crystal-controlled oscillator is held constant to a high degree of accuracy by the use of a quartz crystal. The frequency depends almost entirely on the dimensions of the crystal (essentially its thickness); other circuit values have....
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This is a simple hardware computer interface and Linux program which can be used to control the most commonly used buttons on any consumer Family Radio Service (FRS) or General Mobile Radio Service (GMRS) radio. There are 22 available FRS/GMRS frequencies in....
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The Motorola MC145158 is a dual-modulus, serial-input PLL frequency synthesizer which is commonly used in older Motorola cellular phones. Refer to the MC145158's datasheet for the nitty-gritty technical details. The MC145158 is no longer manufactured, but....
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A fairly simple "divide-by-1000" circuit which was first designed by Zeljko Bozic, S52ZB, in a 2006 issue of VHF Communications Magazine. The idea of this project is to extend the range of older (and cheaper) frequency counters. You can often find 100 MHz....
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A RF spectrum analyzer is one of the most useful tools an experimenter can have. The spectrum analyzer project shown here will be a slight improvement on the " Spectrum Analyzer for the Radio Amateur " ( Part 2 ) project from Wes Hayward (W7ZOI) and Terry....
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This section will list several projects which will allow you to build your own RF design test equipment. Microwave construction techniques and basic electronic skills will be required on some projects, but the tools you can make will equal what the so-called....
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This project is designed for the entry level laser experimenter. The circuit allows any two computers with serial (RS-232) communication capability to communicate over 200 meters using a laser beam. A low cost transmitter only circuit is also presented here....
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The 6JS6C tube is a TV Deflection Tube, or "Sweep Tube". Although not meant for transmitting, it exhibits sufficient performance for RF operation through 30 MHz. Each tube can dissipate 30 watts of plate power. The base is a 12-pin socket. There will come a....
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An audible field strength indicator (AFSI) lets you listen to changes in radio signal strength so that you can use your eyes to look for concealed antennas. Using inexpensive, easy-to-obtain parts, the following design combines a sensitive amplified field....
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This PIC software combines frequency counter and frequency lock functions. By adding couple of transistors and operation amplifier TL082, it is possible to lock the LC oscillator frequency. Frequency reference is formed from the measured frequency itself....
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There are other display methods than the original 8 led frequency counter has. They are perhaps easier to read and may have a format that fits better to the front of your QRP equipment. Here some examples of binary decimal displays are given. Mostly the the....
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The RF signal is split into two signals that are shifted 90 degrees out of phase (one plus 45 and one minus 45 degrees). Both are mixed to audio frequencies. The two audio signals are again shifted 90 degrees out of phase (again one plus 45 and one minus 45....
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The performance of the 80 meter CW transceiver using the phase method for side band suppression is very good. Construction was easy with all good obtainable standard electronic components and without the expensive or complex crystal filter. Almost nothing is....
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After some time of no building activity, the dark afternoons and less busy week-ends has come finally. Perfect time of the season to build a new rig. See what is being done on my bench. I like this way of start, because of easy modelling a components layout.....
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Most modern transceivers have a built in interface. These interfaces work well in digital modes, but seem to lack support in analog voice modes. A case in point is the Yaesu transceivers that only permit the use of their internal interface when the....
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I currently have three: a really old optoelectronics Opto-7000 which I don`t use much, a newer Mitronics MIC-1028, and my most recent acquisition, a used Tektronics 2236 `scope purchased at Dayton 2009, which has a very handy frequency counter built-in. I....
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Anyone who is interested in home construction will at some time or other have the need to measure the inductance of small coils. This can be a difficult problem, as commercially made equipment of sufficient accuracy is often far too expensive for occasional....
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The inspiration for the project came after attending the HamRadio 2000, Millenium Ham Meet @ Hyderabad (December 22, 23 & 24) where I met Grand Masters like VU2NR and VU2RM, OM Raju and OM Rao respectively. VU2NR`s newest design the NR-80 inspired me on....
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The main characteristic of the transceiver presented below is the simplicity, but in the same time giving good performance, with a minimum investment. The radio is based on MC3362 ( buy ). This integrated circuit its an FM receiver, double conversion, which....
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This note will review the process by which VCO (Voltage Controlled Oscillator) designers choose their oscillator`s topology and devices based on performance requirements, components types and DC power requirements. Basic oscillator design specifications....
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A number of ham radio operators have made their start on the 10 GHz amateur band using commercial-surplus microwave transceivers made by M/A-Com. These units were originally built in white-painted metal enclosures and are known as "White Boxes" They can be....
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I usually can`t hear the doorbell when I`m in the basement. This project describes how to add an inexpensive remote doorbell to your existing household doorbell. My doorbell runs off of a 24VAC transformer that is live all the time. Someone presses the....
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This project is a combined temperature and humiditymeter. It is an improvement on my PIC-based humidity meter and my PIC and AVR thermometers. I use an ATmega164, which as lots of I/O and memory. The humidity sensor is a HS1101, made by Parallax (p/n 27920)....
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This article describes how to build a general purpose DTMF decoder with a low-price chip from MITEL. The circuit supports DTMF squelch based on 3 digits station ID (full 999 combination). It also supports decoding of 4 additional commands - station ID plus....
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One thing we should keep in mind is that the EC10 is now a vintage receiver, it has collector appeal. Any-thing we do should really be carried out in a manner that preserves the original state, most of the following adheres to this. Things like replacing all....
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I was asked by the MDRC committee of the day if I would like to take on the role as Electronic components and project officer, I didn`t see any problem with this and agreed. After being elected into the position I soon found out that a little more time would....
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The TMB-1 is an RF amplifier unit / receiving accessory that can be used with a low-impedance broadband loop, a high-impedance terminated loop (such as a Pennant, Flag, or Kaz Delta), and whip (telescoping rod) antennas. This particular design is optimized....
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The purpose of this document is to answer the question of why things are done in a certain way and why certain components are used instead of others. The circuit below is a representation drawing to be used for explanation, but with some refinement could be....
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This diagram comes from the Progressive Communications Receiver that is in most of the latest ARRL Handbooks. This amplifier is used anywhere an IF amplifier is needed. W6BKY has a receiver article at Hamradio-online that shows how to build this circuit on a....
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Apply power to the frequency counter and set the coarse (top pot) and fine (bottom pot) adjustments to show zero frequency on the display. Turn the pots counter-clockwise to set to zero. Sometimes the counter will show all squares and no digits. Disconnect....
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One of the best RF amplifiers ever published was Wes Hayward`s post mixer amplifier in the Progressive Communications Receiver. It quickly became known as a great high level RF amplifier. With a standing current of 50ma, it takes a very strong signal to....
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This oscillator is a variation of the oscillator presented by Ulrich L. Rohde, DJ2LR, in his article "Evaluating Noise Sideband Performance in Oscillators", Ham Radio, October 1978, Page 51. The original circuit is at the bottom of the web page "4 MHz....
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Whenever there is a need for battery-powered lighting, like for camping, solar powered cottages, cars, boats, planes, or emergency purposes, fluorescent lamps have a great appeal. Firstly, they are very much more efficient than glow lamps, so they produce....
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The design presented here is a little bit unusual in its arrangement, but offers some advantages over the usual designs that I will explain in the following paragraphs. First, let`s start from the basics: A linear power supply has a transformer that steps....
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This little transmitter is suitable for less demanding Doppler propagation measurements. It is designed for use on 80m, but can be easily adapted for 40m or 20m. The output is about 500mW of unmodulated carrier, with a stability of about one part in 106, or....
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There are two main types: the most common is the Wein Bridge oscillator variety, which has low distortion, but offers only sinewave output and can suffer from amplitude bounce as you change frequency. The type which offers greater versatility of waveform and....
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This design came about as a result of efforts to design a high stability reference which locked to a 10MHz source. With some minor hardware adaptation and completely new firmware, it proved possible to design an excellent GPS Disciplined Oscillator (GPSDO)....
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The VNGBOX micro needs to produce a very accurate, high resolution and very noise-free DC control voltage to steer the reference oscillator phase accurately. Any noise on this signal will result in noise on the reference; any non-linearity, especially any....
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DDS VFOs work very well with single conversion SSB radios such as the Codan 6801, 6924, 7727 and 8121, and the AWA Teleradio 110H. See the Recycled Radios page for more information about suitable Codan radios. Other commercial and marine transceivers with....
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The goal was to convert this radio for operation on the 70cm amateur radio band. This was unsuccessful as the VCO will not oscillate at the right frequencies for 70cm operation (the VCO control voltage bottoms out before the VCO gets anywhere near the 70cm....
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Following a power interruption, all relays assume their previous state before the power interruption. (relay states and PIN are stored in non-volatile memory) An Motorola MC145436 DTMF decoder is used, this IC is clocked with a common 3. 58Mhz NTSC colour....
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This classic tube amplifier used to be the best value on the block. Fifteen years ago you could buy one of these for $25. This amp was designed to be inexpensive and to get maximum performance for dollar paid. At the end of it`s sale it sold for about $100....
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The circuit diagram is shown to the right. You can get a larger version or a PostScript version if you prefer. The design is based around a Microchip PIC16F628A microcontroller. At the time of writing, this device is available for less than one pound from....
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The congestion of the ether is becoming so great that efforts are continually being made to extend the channels of communication to higher frequencies. Wavelengths as low as 12 metres are now commonplace, but attempts to work below this are fraught with many....
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A laser pulser using the same laser diode LI does. I made the pulser so it could be adjusted from 50 to 20, 000ppm. I tested that on my LIs and rx65, they only alert to pulses from about 100 to 200ppm. I also wonder if my pulsure would work as a jammer if I....
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This is basically how the Scorpion jammers work except that instead of sending back a shifted doppler corresponding to a certain speed, they send back a constantly varying doppler shift where some units won`t display a reading while others display constantly....
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The PA output Pi section consists of 2 variable Cs (20 - 120pF and a second (home made) 50 - 450pF switched in for the lower bands by a simply modified 12v power relay). The anode choke (200t, 24swg 5" long on 1" dia PTFE tube stock) is mounted directly onto....
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Build this circuit using a Digi-Key Electronics Barrel Crystal (CA-301), 15 Mhz for a standard output frequency of 150. 00 Mhz. If you want to customize the frequency, follow the directions below. I usually build this circuit to operate between 150 to 165....
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This circuit operate between 150 to 165 Mhz. The Crystals I use Are The Digi-Key Electronics Barrel Crystals CA-301 Type which cost a couple of bucks per crystal. Virtually any Fundamental Crystal between 14 and 17 Mhz will output a frequency of between 140....
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The DPT Transmitter is a dual powered Voice Transmitter that came about from quite a few request for a transmitter that would function both at power when long range was needed and with a "switch that could be thrown" for a smaller battery consumption when....
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This circuit has to be one that breaks all the internet records. According to the counter on the website above - Top Right (arroncake) - as of May 3, 2013 - it has received 760, 191 views with 412 comments, and today alone - 116 Views. It appears that an....
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The video transmissions from this unit can be received on a small Portable/Tunable and battery operated TV set such as the ones you find in flea markets, etc...