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Small bug using SMT surface Mount technology - Before I tell you about this amazing little project, let me say one thing. You have to be an expert at soldering to put it together. The main difficulty is the surface-mount transistors. All the rest of the components are easy to fit, once you get over the shock of their size, but the transistors are not only microscopic, they are temperature sensitive. They must be soldered quickly with a DELIC ATE iRON at the RiGHT TEMPERATURE. __ Designed by Collin Mitchell
Small FM transmitter SMD - This SMD FM transmitter has an operating frequency of about 80 to 115MHz. Under reasonable circumstances you will be able to receive its signal at a distance of about 200 meters. Although it is low-power, it might be illegal in your part of the planet. __ Designed by Oscar den Uijl
Small Forms Programmable 4- to 20-Ma Transmitter - 04/17/03 EDN Design ideas: One of the key challenges in the design of 4- to 20-mA current transmitters is the voltage-to-current conversion stage. Conventional transmitters use multiple op amps and transistors to perform the conversion function. These approa Design by Alan Li and Jeritt Kent, Analog Devices, Bellevue, WA
Small Radio Transmitter - The circuit is (of course) only mono, and accepts an audio input from either a microphone or other source. The input impedance is 1Mohm. The input sensitivity is 5mV and the max input signal is 10mV. The transmitted signal can be picked up on a FM radio. The circuit can be used for short-range transmission, eg. for wireless microphones. __ Designed by Dan Evans
Small TV transmitter for CCTV observation - Circuit diagram only __ Designed by Jack Donio
Smart VOX from Jet Propulsion Laboratory-Nasa - For creating a COS signal from a radio that doesn't have one. This circuit was developed to control the retransmission of NASA Select audio over JPL's W6ViO repeaters. __ Designed by Randy Hammock KC6HUR and Jan Tarsala WB6VRN
Solar Powered FM Bug - There are many miniature FM transmitter (bug) circuits online, this one is unique in that it runs completely on solar power. No battery is required. As long as the sun is shining on the PV panel, the circuit will transmit. The bug is useful as a "remote ear", and can be used for anything from listening birds to surveillance work. The mic preamp and oscillator circuits were borrowed from a common circuit found around the internet, I added a regulated solar power supply and an RF amp that extends the range and improves frequency stability __ Designed by G. Forrest Cook
Spark gap Transmitter - The first thing I want to stress is that "SAFETY WAS NOT A MAJOR CONCERN" during the days of Spark, some of the methods used were VERY DANGEROUS. Now that I have said that, let me move on. There was a certain amount of excitement that was assoicated with Spark Gap transmitters. Without getting into the theory or design of these Spark Gap Wireless transmitters, let me attempt to give you an over-view of their operaton __ Designed by w1fji
Spark Transmitter! - Now this isn't really for QRP (in fact, it's not at ALL for QRP) , but it was in the projects list, and since the original poster included it (as a joke) , I thought I'dmake it available too. __ Designed by Harry Lythall-SM0VPO
Spy FM Transmitter Bug - Here's a tiny one transistor spy FM transmitter bug that operates from a single 1.5V AA battery. Main advantage of this circuit is that power supply is a 1.5 Volts cell (any size) which makes it possible to fix PCB and the battery into very tight places. Transmitter even runs with standard NIC d rechargeable cells, for example a 750mAh AA size battery runs it about 500 hours (while it draws 1.4mA at 1.24V) which equals to 20 days. This way circuit especially valuable in amateur spy operations. MinI FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps. When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance. I'veseen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc.__
SSB ADAPTOR - Build this simple adaptor to receive single side band SSB on short wave AM receivers__
SSB Transceiver, Transmitter Section - For the transmit mixer, I used a simple single ended JFET mixer. The FET is a J113. The inductors are TOKO KANK3334. You can wind your own on TOKO, or similar formers PRI = 18T SEC = 3T. The transformer at the output of the first stage is 6 Turns, bifilar wound on a ferrite toroid, of the same type used for the RX mixer. I used 2N4427's for both stages. The 2N3866 or 2N5109 should also be suitable. Gain is about 30dB, more than enough to bring the 1mW, from the TX mixer, up to several hundred mW. Use a heat sink on both transistors. __ Designed by EI9GQ homebrew radio
Standalone Multiband WSPR beacon transmitter (MEPT)-PDF file - The following is a design of a standalone MEPT beacon used for WSPR broadcasts [2]. it is based on a Si570 programmable crystal oscillator (silabs.com) which is controlled by means of an AVR attiny45 microcontroller. The Si570 device is FSK modulated by the AVR via a sequence of i2C control commands that are sent to slightly change the frequency for every transmitted WSPR symbol. __ Designed by Guido, PE1NNZ
StarTech CM108 based USB sound adapter conversion article - For AllStar (Asterisk) VoiP __ Designed by Kevin Custer W3KKC
Stereo FM Transmitter - This is a small stereo FM transmitter. Output can be tuned from 88 to 108Mhz and the transmitter can be battery powered or be used with presented low voltage power supply. This circuit is based on the Rhom BA1404 datasheet. The maximum voltage should not exceed 3V. The IC can be driven from a 7805 Regulator with a couple of 1N4001 diodes to reduce the supply voltage to about 2.8 Volts. RF output power is typically 500mW but range depends upon antenna coupling and efficiency, environment and size of antenna. A small telescopic whip has an expected range of at leaset 100 metres or more.__
Stereo FM Transmitter with BA1404 - Circuit of stereo FM transmitter of of high quality using integrated circuit ba1404 for mp3, mp4, ipod, computer, radio of the car. Transmit of your equipment of portable audio for the radio of your car, transmitters of fm of low potency are the ideal for transmission wireless of audio sign for fm receivers. Mainly in that case that is treated of transmitter of FM stereo with ba1404. The heart of that circuit is the circuit integrated ba1404, that is a minI fm transmitter, that already counts with the necessary internal circuits for transmission in fm. just being necessary to increase some components discman or any other audio source turning the wireless. if you already set up other transmitters of transistorized fm it will see that when setting up that with having integrated BA1404, that the quality of the sound and the frequency stability is excellent. Besides the but it presents easy assembly__
Super Simple Circuit FM Transmitter - FM transmitters can be complicated to build, but not this one. it’s about the easiest you can possibly make. And though the science of radio is well understood, there’s a magical, emotional quality about it that we don’t often stop to appreciate. You will not forget the first time you pick up a transmission broadcast from a device you soldered together, yourself, from a few bits of copper, carbon, plastic, and wire.__
Super Simple Circuit iPod FM Transmitter - FM transmitters can be complicated to build, but not this one — this iPod FM transmitter about the easiest you can possibly make. And though the science of radio is well understood, there’s a magical, emotional quality about it that we don’t often stop to appreciate. You will not forget the first time you pick up a transmission broadcast from a device you soldered together, yourself, from a few bits of copper, carbon, plastic, and wire.__
Super Spy Transmitter Bug - A very small home made FM transmitter Bug using a single transistor and with a transmission range of 200 meters. This FM transmitter Bug is very easy to build. The size of the circuit board is ONLY 22mm x 10mm.__
Superregen Receiver for FM broadcast or Aircraft band AM reception - This is the receiver I was bragging about on the Radio index page -- the receiver that is so sensitive it can hear the local oscillator inside a small transistor radio 30 - 50 feet away. Build one of these little gems and you will be able to hear aircraft pilots many miles away with nothing more than a 24" whip antenna. __ Designed by Rick Andersen
Supporter for my fiber glass antenna mast - This is my Homebrewed fiber glass antenna mast supporter used for a 10 meter tall fiber glass antenna mast (made in May 2005) __ Designed by Bjarke Korsgaard
Surplus 30 to 80 MHz filter - This is a Radio Astronomy Project __ Designed by Radio-Sky Publishing
Surveillance Transmitter Detector - This circuit can be used to "sweep" an area or room and will indicate if a surveillance device is operative. The problem in making a suitable a detector is to get its sensitivity just right, Too much sensitivity and it will respond to radio broadcasts, too little, and nothing will be heard. __ Designed by Andy Collison
SW Regenerative Receiver - Sensitivity and selectivity are the major concerns of a short wave enthusiast when he looks up for a receiver. Commercial communications models with superhet circuitry surely satisfy his requirements, but these are expensive. He would rather go for a Homebrewed radio, being a regenerative receiver an affordable choice __ Designed by Ramón Vargas Patrón
Switch Transmitter - A door which opens, a drawer slides out, a switch turned on or a letter in your mailbox: this transmitter can detect all! it is battery operated and can be placed practically everywhere. Uses a single long-lasting battery. __ Designed by Projects & Ideas from Nutchip.com
SWR Bridge - Ham Radio - Other __ Designed by Guy Roels ON6MU
SWR Bridge 1 to 1000 Mhz (1GHz) - This SWR bridge is not my own invention, OZ3SW and OZ9MO has improved the design after DJ7VY construction in ukw-berichte 1/83. This is a construction set made for the members of Frederikssunds EDR Club, all I did was a bit of gluing and soldering. Thanks for all the hardware help, parts help, calibrating and measuring ! you know who I mean ! ! __ Designed by Thomas Scherrer OZ2CPU
SWR Direction Coupler 5 to 500 Mhz, made to be used with the Digital Wattmeter - This Direction coupler can be used from 5 to 500 Mhz. I have not tested it above 500 Mhz
This design and PCB is not my own invention, but an old project from my local EDR club. it can be used with the Digital Wattmeter that has a special measurement screen that displays the difference between two signals. This difference is displayed both in dB and SWR ! ! __ Designed by Thomas Scherrer OZ2CPU
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