RF Circuits
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Suitable for amateur use, this 1.5-W transmitter runs on a 12-V supply. Ql is an oscillator using a surplus FT2.. -
This transceiver has a 3-stage transmitter and a direct-conversion receiver. Ql is the transmitter"s oscillator, an.. -
This VHF VCO circuit is suitable for 30 to 200 MHz. Q1 can be replaced by a 2N3563 for operation above 100 MHz.. -
A simple FM wireless microphone uses a single BC183C transistor as an audio amplifier. A 2N3565 can be substituted. .. -
This antenna might help to reduce power-line noise. A plastic hula hoop or conduit 3 feet in diameter, covered with aluminum foil as a shield is used for LI and L2. LI is two turns and L2 is one turn, threaded through the loop. SI selects 160- or 80-m.... -
The HF/SW receiver preamplifier is comprised of a broadband toroidal transformer (LI-a and Ll-b), LC network (comprised of a 1600-kHz, high- pass filter-and a 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wire wound on an Amidon Associates.... -
A pair of diodes and a quarter-wave transmission line are used as an automatic TR switch. D1 and D2 conduct during transmit periods, short- circuiting the scanner input. In this mode,-the K-wave line appears as an open circuit... -
This antenna tuner is suitable for use with low-power (less than 5 W) transmitters or SW receivers. S2 selects inductance and S2 connects the 365-pF capacitor to either the transmitter or the side of the inductor. The tiny tuner is comprised of a tapped.... -
This preamplifier has a built-in regeneration control boost gain selectivity. CI is a single or multi-gang AM broadcast-band tuning capacitor. LI is a ferrite loop antenna, tapped at about 15 to 25% of total turns. This circuit should prove useful for.... -
An LM311 comparator converts a small analog signal to a digital level for the DC4046 phase-locked loop, which is configured as a first-order FM demodulator. This demodulator works with a 50-kHz FM modulated input signal. It has applications in FM light beam.... -
The LR inputs are summed, dated and drive a comparator. The comparator senses level and generates a transition when audio inputs go above or below preset thresholds. The number of these transitions (corresponding to rapid volume changes) are integrated and.... -
The FM modulator is built with a Motorola MC1648P oscillator. Two varactors, Motorola MV-209, are used to frequency modulate the oscillator. The 5000- potentiometer is used to bias the varactors for best linearity. The output frequency of approximately 100.... -
Note that Tl and T2 are TOKO, including part numbers for the coils Tl and T2. The direct-con-version receiver shown uses a double-tuned input network made from readily available TOKO coils. IC1, an NE602, acts as a VFO and mixer, with the output being an IF.... -
The VLF whistler receiver is intended to listen to natural radio noise and signals that occur below 20 kHz. LI is a large loop antenna that is 250 to 300 turns #26 gauge wire on a form 3` diameter... -
An NEC602 is used as a mixer with a zero IF frequency output, U2 acts as an audio amplifier. This receiver is primarily for SSB and CW signals. Tl and T2 are 10.7-MHz IF coils used in AM/FM transistorized radios, etc... -
Integrated circuit Ul (an NE602 double-balanced mixer) is a combination oscillator and frequency mixer. Signals from the antenna input (at Jl) are fed through dc-blocking capacitor C1 to the RF-gain control, Rl, and fed to the input of Ul at pins 1 and 2..... -
This HF SW receiver preamplifier is comprised of a broadband toroidal transformer (LI-a and Ll-b), a complex LC network (comprised of a 1600- kHz, high-pass filter and a 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wire wound on an Amidon.... -
The MAR-x preamp shown will cover up to 1.5 or 2 GHz with the correct MAR-x IC. ATTN1 should be omitted for low noise-figure.appli cations. ATTN1 and ATTN2 provide a means of limiting possible termination range,.. -
The circuit has a frequency response that ranges from 100 Hz to 3 MHz; the gain is about 30 dB. Field-effect transistor Ql is configured in the common-source self-biased mode; optional resistor R1 allows you to set the input impedance to any desired value..... -
The SD1143 transistor provides a gain of about 14 dB in this circuit. It uses the fact that a 175-MHz device has a much higher gain when used at lower frequencies. The amplifier was originally designed to be used with a transverter. .. -
Except for the coupling and decoupling capacitors, IC1 is a complete wideband amplifier that has a fixed gain of 20 dB to 450 MHz. No external compensation is required. since the NE5205 functions as a gain block, two or more cart be easily cascaded to.... -
This linear amplifier delivers 10-W PEP output; with 1.25-W drive on 10 m. Tl, T2, and T3 are 10 turns of bifilar windings on an FT-50-43 toroidal core. The transformers are broadband. Filters for other bands, if desired, are shown. Note: use #26 wire for.... -
The low-cost Mini-Circuits MAR-X series of chips offer the RF builder a real advantage, with their inherent 50- input and output impedances (needed for RF systems). An MAR-1-based receiver/scanner preamplifier is shown. Ci and C2 are chip capacitors. Use.... -
The circuit, shown will produce up to 5-W RF output in the 40-m (7 MHz) amateur band. The coils shown are wound on toroidal cores (Armdon Associates Inc.). The part numbers are given in the schematic... -
Motorola MWA 110, 120, or 130 are wideband amplifier ICs. This wideband preamp circuit can be used in many applications. Keep the leads short when constructing the circuitry. PC board layout (shading represents copper) and parts layout. X is the feedthrough.... -
Op amp Ul and its associated components comprise the 67-kHz bandpass filter. A twin-T network, comprised of four 1100-12 resistors and four 0.0022- capacitors, is connected in the feedback network of the op amp. That gives some gain at 67 kHz and heavy.... -
A BA1404 IC is used to generate a complete FM MPX signal. The chip contains all of the necessary circuitry. CI and R3, and R4 and C4 provide pre-emphasis. The transmitter runs on a single AA cell. L3 is 3 turns of #20 wire on a Ke drill (for a form). L3 is.... -
This system operates on the principle that capacitance loading of an oscillator will lower its frequency. When a foreign body comes into contact with touch plate, the frequency of Ul is lowered... -
Using a Motorola MC2833 one-chip FM transmitter, a few support components, and an MPF6660 FET RF amp, this transmitter delivers about 3 W into a 50- load... -
The three schematics represent three building blocks for a 10-meter SSB transmitter. Or these blocks can be used separately as circuit modules for other transmitters. The VFO board uses an FET transmittal oscillator, the VFO signal is mixed in an NE602.... -
This low-power video transmitter is useful for R/C applications, surveillance, or amateur radio applications. Seven transistors are used in a crystal oscillator-multiplier RF power amplifier chain, and a high-level video modulator. A 9- to 14-Vdc supply is.... -
The vacuum tube is still alive and useful in some applications, as in this CW transmitter, The circuit was built in old-fashioned breadboard style on a wooden base. Old table radios are a good source of parts for this circuit. V3 is used as a ballast....
New Circuits
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This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of.... -
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is.... -
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to.... -
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This.... -
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the.... -
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,.... -
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the.... -
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power.... -
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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