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Modulator Circuits
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Last Updated: January 01, 2018 04:02 AM

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UHF-TV Preamplifier - Circuit only __

Unamplified Four Foot Box Loop - I have been using a three foot box loop that Don Moman in Edmonton, Alberta put together for me for several years now.  I have been more than happy with its performance, and I have a long list of leggings to prove it, However I have been wondering how a four foot loop might help out my DX'ing by producing either a better signal or deeper nulls.  I set out to build this four foot model in every way.  My four foot loop did carry on one important idea that Don Moman's loop had and that was the less metal the better.  The four footer has as does the three footer only four screws and two bolts.  The rest of the loop is wooden thus keeping the antenna's pattern as true as possible. __  Designed by Bruce Carter

USB FM Transmitter - Here is a simple USB FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio by connecting it to an USB port.  The circuit use no coils that have to be wound.  This USB transmitter can be used to listen to your own music throughout your home.  To keep the fm transmitter circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606.  This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency.  The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit.  The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency. __

USB FM Transmitter MAX2606 - This MP3 Player FM transmitter can be used to listen to your own music throughout your home.  The transmitter circuit use no coils that have to be wound.  When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player.   __

USB Mono FM Transmitter - This small FM transmitter with a range of about 50 meters designed for connection to the USB port.  With lots of mini-transmitters then you have a comprehensive, action-packed radio program.  Due to the power supply via the USB port of a high frequency stability is achieved.  Alternatively, the receiver, a battery 5 to 12 volts to operate. __

V7 VHF FM Transmitter  - The circuit itself is fairly conventional, with a couple of small refinements.  It all begins with TR1 (BC547) in an inverted Hartley oscillator configuration.  The feedback to the Base of TR1 is via a small 4.7pf capacitor to help keep the oscillations as weak as possible whilst allowing the oscillator to be a reliable starter __  Designed by Harry Lythall-SM0VPO

Variable Power Supply for the FM Transmitters - This is a fairly simple, yet very versatile workbench power supply.  With a current limit of 1.5 amperes and a variable voltage from 2.7 volts to 16.5 volts on the output of the LM317T, this unit will come in very handy for your diversified electronic projects   (which usually include different DC voltages.  I have used it mainly for supplying my FM transmitters with different voltages, to see the different effects it has on the units.  In fact, I use it for all my FM transmitters.  It has served me well.  and is still serving proudly! __  Designed by braincambre500 @ yahoo.com

Variety of receiver converter projects - The FM broadcast band was moved immediately after World War II from its original spot just below 50 Mc to the present 88-108 Mc band.  Hallicrafters was one company to offer receiving converters for those who had the old FM radio sets.  The offerings included a one-tube converter that fits inside a console and draws power from the audio output tube socket (using an adapter).   __

Veronica 1W FM Transmitter - Veronica 1W FM transmitter is an easy to build transmitter.  Veronica is also known for frequency stability, clean FM signal and uses no integrated circuit.  The Veronica oscillator is actually formed from 2 oscillators which operates somewhere around 50 MHz in antI phase and the 2 signals are combined to form 100MHz FM radio signal.  This kind of circuit design is stable and is amplified up to 1W by 2n4427 transistor.  Veronica transmitter is equipped with a mini-mixer and so you may forget an external mixer.  This consist from T1 transistor which amplifies the microphone signal before it is combined with CD player audio or PC signal.  R1 and R2 are potentiometers (variable resistors) used to adjust the audio level.  The component between R8 and C21 represents the oscillator which generates radio signal.  D1 is a varicap diode (like a variable capacitor or trimmer) controlled by audio signal.  C12, C13 and L1 determines the frequency. __

Veronica 1W PLL FM Transmitter - The VERONICA transmitter is a very stable, powerful, and high quality FM emitter.  Thanks to a PLL, the output frequency is controlled with DIP switches.  Output power is approximatively 1W with a single regulated 13.8v supply ! (see specifications) Features : * High RF output power : 1W * Full 87.5-108MHz range (100KHz increment).  * Very stable output frequency : Crystal reference & Phase Locked Loop.  * Professional input bandwith (fully RDS compatible ) * No complex tuning needed.  * High quality PCB * Full documentation & construction details available __

VHF Condor 16 transceiver modifications - Ham Radio - Other __  Designed by Guy Roels ON6MU

VHF CW TX - I use this simple CW transmitter for working through the RS13 satellite.  Using just 10 Watts and a dipole at 3M above ground, I have made many contacts around Europe and across the Atlantic __  Designed by EI9GQ homebrew radio

VHF FM Transmitter - The circuit is a simple 88-108 MHz VHF FM transmitter circuit.  It is basically a VHF Colpitts oscillator capable of transmitting sound or music to any standard FM receiver.  The circuit is powered by 9V battery which makes it easily portable.  It also has a capacitor microphone which picks up very weak sound signals.  The output frequency can be easily adjusted by potentiometer thanks to onboard MV2109 varicap diode and the frequency stability is quite good.  The range of this transmitter is 100 meters. __

VHF Video Transmitter 60-200 MHz - Here's a simple video transmitter for VHF TV channel will accept baseband video input, hence it can be driven by most CCD cameras and VCR video outputs.  It ouputs roughly 80mW and when used with a 40cm telescopic antenna over 100 meters range is possible. __

VHF/UHF Prescaler - The recommended Prescaler is ridiculously simple.  It consists of just one IC, a TV tuner prescaler, the Philips SAB6456A, which can divide by 64 or by 256.  This chip is widely available both new and in the surplus market at much lower prices than conventional divide by 10 prescalers.   __

VHF/UHF TV Modulator - Simple oscillator that generates a frequency in the VHF or UHF region.  The oscillator is modulated with the video signal and the modulated carrier wave thus generated is fed into the TV set's aerial input via a cable.  Then all that remains to do is tune the TV to the correct frequency.   __

Video Modulator 251025 Schematic-Commodore 64 - Takes in S-video format video + mono audio, outputs S-video, composite video and modulated RF signal__ 

Video/Audio Wireless Transmitter - Television signals operates as two separate transmissions.  One for the video and the other for sound.  And just like our project, two different devices are going to be built.   __

Voltage Controlled Mixer with Modulator - Schematic only, no circuit description __  Designed by John Simonton

Waveform Generator Demodulates FM Signals - 10/10/96 EDN-Design Ideas - The circuit in Figure 1 uses the phase-detector signals of a precision waveform-generator IC to perform FM demodulation.  In a standard application, the IC's phase-detector input and output synchronize the chip's output frequency to that of an applied signal.  If the signal is FM, you can extract the demodulated signal from the phase-detector output.  The waveform generator - Circuit Design  by  Doug Vargha, Maxim Integrated Products, Sunnyvale, CA

WBFM TX V7 - The circuit is identical to the V7 VHF FM Transmitter but with a few small additions.  TR1 (BC547) is an inverted Hartley oscillator which based upon an inductor fabricated on the PCB.  This makes it megga-stable, and setable.   __  Designed by Harry Lythall-SM0VPO

Wide Band RF Amplifier for 10MHz-500MHz Input - This paper describes an RF amplifier circuit which is suitable for the frequencies between 10MHz and 500MHz.  These kind of amplifiers are called wide band amplifiers.   __  Designed by Yilmaz Kalafat, PE1PYJ

Wireless PLL Stereo FM TX with LCD - Now you can use your MP3 Player to listen your favorite tunes through any FM stereo receiver.  Wireless FM transmitter wirelessly connects portable music players to your car or home stereo quickly and easily.  Just plug the FM Transmitter into the headphone jack of your MP3 or any audio source including iPOD, PDA, CD Player, Cassette player or connect it to your PC or laptop computer.  Tune your card stereo or receiver to the clearest FM frequency, and enjoy your digital music with full sound and convenience.   __

X10 RF daughter board- receiver - Schematic only __  Designed by Peter Jakab

XTAL-Controlled FM TX (V6) - My FM Wireless microphone V5 has been very popular, both as a beginners project and as a kit.  It is interesting that it has also been the biggest cause of lots of e-mail, the most common question being How can I make it crystal controlled?.  The oscillator can be made crystal controlled; replace the 2p7 with a 5th harmonic crystal.  The oscillator will then be very stable, so stable in fact, that it cannot even be modulated!  This means that you could only use it to send CW (morse code)  __  Designed by Harry Lythall-SM0VPO

ZN414 AM Receiver - An AM portable radio receiver made from the ZN414 IC.  The ZN414 IC has now been replaced by the MK484 which is identical in performance and pinout.   __  Designed by Andy Collison

   

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