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Modulator Circuits
Modulators:  #'s - A        B - F        G - M        N - T        U - Z

Last Updated: October 24, 2017 02:55 PM

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Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

2 Transistor FM Transmitters   -  While there are a plethora of similar 2-transistor schematics available, this one is above average.  A major improvement overlittle 1-transistor circuit that we've discussed previously, this transmitter consist of two stages.  first transistor is used to amplify audio,  __

2 Transistor LED Flasher   -  This 1.5 volt led fasher runs more than a year on a single 'd" cell and alternately flashes 2 LEDs at about a 1 second rate.  The circuit employs a 74HC14 CMOS hex inverter that will operate at very low voltages   (less than 1 volt).  One section is used as a squarewave oscillator   (pins 1 and 2) , while the others are wired to produce a short 10mS pulse on alternate edges of the square wave so the LEDs will alternate back and forth.  The output sections each use a capacitor charge pump to increase the voltage for the LEDs __  Designed by Bill Bowden

2 Watt FM Transmitter   -  This 2 Watt FM transmitter will provide 10km range in good weather conditions.  Use dipole antenna for maximum range.  Transmitter can be tuned between 88-108 MHz with c5.  BB204 could be replaced with conventional led   (big) with reverse bias   (no light given in correct polarity).9v power for 2km transmission with good sound quality and up to 18v for 10km range.2N3553 RF transistors may be replaced with 2N4427 or 2N3866. __

200mW FM Transmitter Project   -  This type PCB is the same style of design used on the 7 Watt FM Transmitter.  Take a look at the digital snap shot on the 7 Watt webpage.  Notice on that picture.  all of the components that are soldered onto the copper.  are both on the same side of the PCB.  I decided to use this style as it was very quick and easy to change out components.  during the many months of experimentation.  So, there are no holes to be drilled on the PCB, except for the four mounting holes __  Designed by braincambre500 @ yahoo.com

20W FM Amplifier   -  This Power amplifier is equiped with two Philips bipolar transistors : the BLV10 & BLW87.  As lots of FM amplifier design, the RF transistors are in a class C bias.  The FM amplifier has a 21 dB gain with a 55 to 65% efficiency.   __

23cm ATV FM Transmitter   -  Schematic only __  Designed by va3iul

2-5 Km Long Range FM Transmitter   -  The proposed long range transmitter circuit really is very steady, harmonic free design which you can use with standard fm frequencies between 88 and 108 MHz.  This will likely encompass 5km spectrum   (long range).  It includes an extremely consistent oscillator for the reason that you employ LM7809 stabilizer that is a 9V stabilized power source for T1 transistor and for frequency realignment that may be reached by means of the 10K linear potentiometer.  The output strength of this long range rf transmitter is approximately 1W.  Transistor T1 is employed as an oscillator stage to present a small power steady frequency.  To fine-tune the freq.  apply the 10k linear potentiometer this way: should you moderate, in the direction of ground, the freq.  would probably decrease but when you fine-tune it in direction of + it would climb.  Essentially the potentiometer is needed just as a flexible power source for the a pair of MV2019 varicap diodes.  Both of these diodes function as a changeable capacitor whilst you regulate the pot.  By tweaking the diode capacitance the L1 + diodes circuit renders a resonance circuit for T1.  Feel free to employ transistors similar to BF199, BF214 however be careful not to use BCs.  At this point you donít receive yet the long range fm wireless transmitter due to the fact that the electric power is fairly reduced, a maximum of 0.5 mW. __

250mW FM Transmitter Amplifier   -  This project is a simple 2-transistor VHF power amplifier, with about 16dB gain, and requires no tuning or alignment procedures.  Wideband techniques have been used in the design and the circuit is equipped with a "lowpass" filter to ensure good output spectral purity.  The project has been designed for assembly on a single-sided printed circuit board.  The circuit is specifically designed to amplify the output of 7mW to 10mW WBFM transmitters   (wide band) to a final level of 250mW to 300mW. __

250mW FM VHF Transmitter   -  This FM VHF transmitter will output approximately 250mW of RF power using a 2N3866 output transistor and can operate between 75MHz and 146MHz.  It utilities a variable high gain audio pre-amplifier which can detect voices 40 feet away using an electret microphone.  Using a NBFM scanner, ranges over 5KM have been achieved using a 48cm wire antenna.  Coils are 22SWG 7mm air core.  L1 and L2 should be 6 turns for 75MHz to 85MHz, 4 turns for 85MHz to 100MHz and 3 turns for 100 to 146MHz.  For frequencies over 100MHz the Crystal will be higher than 20MHz hence the base emitter capacitor should be 47pF.  L3 is a 4.7uH choke.  It is ideal to tune up this circuit using a wave detector meter placed a few inches away from the transmitter. __

25W RF Amplifier   -  RF amplifier with 25W of power for 88-108MHz FM transmitters __  Designed by suthus55 @ hotmail.com

27 MHz FM Receiver   -  The FMR-201 is a crystal controlled single channel receiver, comprising of receiving, decoding and open collector output sections.   __

27MHz/ 49 MHz Walkie Talkie   -  Lots of people are requesting walkie-talkie and RF remote control schematics, so here is some.  Building these circuits needs special equipment and expertise in RF circuits.  If you are going to experiment with these circuits, please __  Designed by Peter Jakab

28W FM Broadcast Transmitter Amplifier 88-108 MHz   -  This RF Amplifier designed for FM broadcast using a single 2SC1946 VHF Power Transistor.  This 10-30W RF amplifier circuit provides an appropriate power boost with an input of 1-3 watt.  Tower are 30 meters high will send signal surrounding air should be around 15 km.  The layout of the 2SC1946 28 Watts FM broadcast RF amplifier has been created with Eagle.  The pcb outline is 100 x 50 mm   (width x height), all bitmaps have a resolution of 600dpi.Use FR-4 single sided photoresist epoxy pcb material for best results. __

2km Long Range FM Transmitter   -  The power output of many transmitter circuits are very low because no power amplifier stages are incorporated.  The transmitter circuit described here has an extra RF power amplifier stage using 2N3866 RF power transistor after the oscillator stage to increase output power to 250 milliwatts.  With a good matching 50-ohm ground plane antenna or multi-element YagI antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometers.  Transmitter's oscillator is built around BF494 transistor T1.  It is a basic low-power variable-frequency VHF oscillator.  A varicap diode circuit is included to tune the frequency of the transmitter and to provide frequency modulation by audio signals.  The output of the oscillator is about 50 milliwatts.2N3866 transistor T2 forms a VHF-class A power amplifier.  It boosts the oscillator signal power four to five times.  Thus 250mW of power is generated at the collector of transistor T2. __

2km TV Transmitter   -  Here is a simple TV transmitter.  The circuit is simple and really quite crude, but it does include MONO sound.  I have not shown the two regulators in the drawing.  These are one 12v DC 1A series regulator chip, and one 8v DC 1A series regulator.  I fed the 8v regulator from the output of the 12v regulator.  The rest of the circuit looks like this.  It is a free-running Variable Frequency Oscillator   (VFO) using just one coil and one capacitor to determine the frequency.  Change this as you will.  The basic circuit uses a 150pf from the Base of the RF transistor to ground, so that TR2 operates as a "common-base mode"   (grounded base) amplifier.  The tuned circuit in the collector and the capacitor from collector to emitter provide tuning and feedback. __

2-Transistor Amplifier   -  It has been interesting analyzing these radios.  You have to give the Japanese credit for even making a radio that can drive a speaker with only 2 transistors!Basically, the first transistor   (Q1) performs double-duty.  It first acts as an RF amplifier, with some of the signal being fed back to the antenna coil to provide some regeneration for better selectivity and sensitivity __  Designed by schematic and circuit description were provided Ronald Rissel

2-Transistor FM Transmitter   -  While there are a plethora of similar 2-transistor schematics available, this one is above average.  A major improvement over the little 1-transistor circuit that we've discussed previously this transmitter___ copy of geocities.com/tomzi.geo page

2W RF Amplifier for 24/23 CM   -  This page describes TX ATV Transmitter for 23 cm with output adjustable from 100 to 250mW __

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