Top Circuits Page 4
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The dynamic mixer combines two audio inputs by adding the primary signal, Input A, to a gain-controlled signal, Input B..
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This stereo mixer has two mono mixers and a modification to the microphone inputs. When a microphone is in u..
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The proposed mixer is designed around four current-driven transconductance amplifiers contained in an SSM2024 from Precisio..
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A simple digital mixer, based on two dual-Schmitt triggers (4583B) and three exclusive-OR gates, uses an RC time-delay circui..
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Three audio circuits are combined in the circuit shown. Each input is coupled to its own level potentiometer (Rl, R2, or R3) an..
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By inserting a high-pass filter section in the IF lead, this mixer is terminated at all frequencies, besides the IF, for oth..
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This circuit is one section of an octave equalizer used in audio systems. The table shows the values of CI and C2 that are needed to achieve the given center frequencies. This circuit is capable of 12 dB boost or cut, as determined by the position of R2.....
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In an adjustable lowpass filter, each filter section uses commonly available components (Figure 1). This example uses filter-section cutoff frequencies for standard inductors and capacitors without the need for any extra components in series or parallel.....
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This simple tone control can be used in may audio applications. It can be added to amplifers, used as a stand alone control module, or even built into new and exciting instruments. It`s one IC construction makes it a very compact circuit, as only a few....
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The composite lowpass filter uses interior constant-k full sections terminated by m-derived half-sections.The design technique is also applicable to highpass and wideband filters (references 3 and 4). Figure 1 shows a schematic of the composite lowpass....
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The meter will show volume and tone control balance between left and right stereo amplifiers. For maximum convenience the meter is a zero-center type. Resistors are five percent or better and the diodes a matched pair. Optimum stereo level and phase balance....
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This preamp and tone control uses the JFET to its best advantage; as a low noise high input impedance device. All device parameters are noncritical, yet the circuit achieves harmonic distortion levels of less than 0.05% with a S/N ratio of over 85 dB. ..
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Outputs from each channel are fed to the two inputs of ICl connected as a differential amplifier. IC2 and 3 are driven by the output of ICl. Output of ICl is connected to the noninverting inputs of IC2 and 3. If the output of ICl approaches the supply rail,....
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This circuit will allow you to set the gain of two stereo channels to the same level. The signal across the two channel-load resistors is sampled by resistors R2. (Values of these resistors will depend upon the power level) For most 20 milliampere LED, use....
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The iriput signal is fed via SKI to the first active stage built around ICl. Configured as a noninverting amplifier whose gain is set by the ratio of R3 and Rl. In this case, the gain is set at unity. This initial stage is required to isolate the following....
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The circuit is based on an inverting op amp using discrete transistors to overcome poor slew rate, fairly high distortion, and high noise problems. The output stage is driven by a constant current source, biased by a green LED to provide temperature....
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A simple single-transistor circuit will give approximately 15 dB boost or cut at 100 Hz and 15 kHz respectively. A low noise audio type transistor is used, and the output can be fed directly into any existing amplifier volume control to which the tone....
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The circuit is a form of the so-called ""Americanized" version of the Baxandall negative-feedback tone control. At very low frequencies, the reactance of the capacitor is large enough that they might be considered open circuits, and the gain is controlled....
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Most audio tone controls affect midband gain, and !bey often create booming or hissing sounds when activated. You can avoid tbese problems by using a dual Wien-bridge filter to provide independent control of tbe treble and bass frequencies. Experiments....
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If your amplifier is fitted with two level controls, it actually offers you a balance control and a level control. A draw..
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This circuit adds a VLF AM component to an audio signal. This effect is widely used in musical instruments. U1C, a phase-sh..
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This circuit is an AGC system for audio-frequency signals. AGC systems usually consist of three parts: an amplifier, rectifier, and controlled impedance. In this circuit the functions of an amplifier and a rectifier are performed by a single op amp. This....
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The rectifier input is tied to the input. This makes gain inversely proportional to input level so that a 20-dB drop in input level will produce a 20-dB increase in gain. The output will remain fixed at a constant level. The circuit will maintain an output....
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A Motorola TCA5500 or TCA5550 can provide a stereo preamplifier system with tone controls. This circuit provides a gain of about 10X, a 14-dB tone-control range, a 75-dB volume control range, and it can operate from 8 to 18 Vdc. IC2 provides 15 V for ICl,....
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This audio processor is based on the Signc tics/Philips TDA3810N stereo, spatial, pseudo-stereo processor, IC. This processor uses a Philips TDA3810IC device, and it functions as an expander, pseudo stereo processor, and audio enhancer. ..
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This approach to automatic level control (ALC) makes use of digitally switched audio attenuators in the signal path. The output level of the system is sensed, compared to a reference, and audio pads are inserted via analog switches...
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This transmitter with a good antenna and under proper conditions of use may have a range of more than 45km. The configuration is made by the rise of the output lamp, which makes it advantageous as regards the fidelity of the emitted signal. The 6V6 lamp is....
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This transmitter works in the short waves from 6MC / S to 22MC / S. Coil L1 is the short wave oscillating coil of the 6SA7 lamp and you will find it ready for trade. Capacitor C1 is variable with a capacity of 0-500pF. The coil L1 consists of 13 coils 3cm in....
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For our strong construction with the two 807 we do not need words. We all know the performance of such a machine. In this construction we have the peculiarity of high upward tension and independent coupling. On the output lamps, resulting in the output power....
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This transmitter consists of three stages. The step of the oscillator with the 6L6 lamp, the amplifier isolator with the lamp 807 and the final stage of the transmitter with the 811 lamp. The coil L1 is requested by the market as a coil of the 6SA7. The....
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It consists essentially of three stages and gives the antenna a power of 300 WATT, provided it is properly tuned. The first tier is an oscillator that has an oscillating coil L1 that will be required by the market as a 6SA7 coil. The coils L2 and L3 consist....
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This transmitter of 255W is depended on the coils we put at it to work in both the middle and the short waves. The power in the antenna is 255W and includes 4 states. The first consists of the EF80 that works as a COLLPITS CLAPP oscillator. Frequency....
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In this circuit, the wearer assembly consists of only one lamp, 6V6 or 6L6, which acts as an oscillator and as an output amplifier at the same time. Coil L1 is the medium wave oscillation coil. Of 6SA7. The coil L2 consists of 50 spools wrapped on a cylinder....
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Is this a transmitter? Medium-wave short-wave consists of three transistors. The transistor AF115, along with the rest of its circuitry, is the oscillator of the device. The circuit of the two OC72 is the low-frequency amplifier (modulator), which forms the....
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This transmitter consists of 5 in total bulbs. 6L6 works as an oscillator. Subsequently the oscillation is guided to the guide grid of 807 which acts as the ultimate amplifier and is the transmitter output lamp. The amplifier consists of the ECC83....
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This transmitter, as shown in the drawing, consists of a 6V6 as an oscillator, then the signal excites an 807 which acts as a buffer. The final step consists of two 807 in Push-Pull. The amplifier consists of three in series double-triodes ECC83 and finally....
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The modulator and oscillator consist of two NPN transistors. The base of the modulator transistor is driven by a bidirectional current source with the voltage range for the high condition limited by a saturating PNP collector to the pin 4 Vreg voltage and....
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This transmitter consists of a keyed crystal oscillator/driver and a high efficiency final, each with a TMOS Power FET as the active element. The total parts cost less than $20, and no special construction skills or circuit boards are required. The Pierce....
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This transmitter is capable of two levels of rf power. For low-power wireless video, like in a house or office, where simultaneous monitoring of program material is desirable without cumbersome hookups, 1-30 mW is available. For longer ranges up to several....
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This is a little transmitter that could be put into a plastic Easter egg. It delivers approximately 1 W of measured rf output into a 50-0 dummy load, and creates no heating problems with the circuit. The crystal is a series fundamental type, and the power....
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In a half-duplex system, information can flow in both directions, but only one direction at any given time. The conventional method of building a half-duplex link requires a separate emitter and detector, connected with directional couplers, at each end of....
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The crystal oscillator, which uses two sections of IC1, a 4001 quad 2-input NOR gate, is a standard and reliable design. The oscillator"s 1.85-MHz, square-wave output feeds IC2, a 4017 divide-by-10 counter. The count enable and reset terminals, pins 13 and....
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This transmitter can be used for transmitter hunts, for remote key finding, or for radio telemetry in model rockets. It can be tuned to the two meter band or other VHF bands by charging Cl and Ll. 11 is four turns of #20 enameled wire airwound, 0.25 inch....
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The unit consists of a direct conversion receiver and 1-W transmitter. The direct conversion receiver VFO is tuned just off frequency from the incoming signal. This difference in frequency produces a clean, strong, and solid audio tone signal. Detect the....
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The oscillator, Q1, is a standard overtone circuit. A fifth-overtone crystal, 80.545 MHz, is operated on the seventh overtone, 112.763 MHz. C6 couples the output of the oscillator to Q2, which operates as a doubler to 225.5 MHz. A double-tuned circuit....
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This is a 3-W, single-circuit board, VFO-controlled CW transceiver for 40 or 30 meters, featuring a direct-conversion receiver with audio filtering, Receiver Incremental Tuning (RIT), and speaker level audio volume. The transmit frequency is generated by....
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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..
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This transceiver has a 3-stage transmitter and a direct-conversion receiver. Ql is the transmitter"s oscillator, an..
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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...
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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...
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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....
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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....
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Running from a 9-V battery, this transmitter can be used as a wireless microphone with an ordinary 88- to 108-MHz FM broadcast receiver. Keep the antenna length under 12 inches to comply with FCC limits. LI is 6 turns of #24 wire wound around a pencil or a....
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Using a 6BW6 vacuum tube, the above transmitter delivers about 5 W output. CI is adjusted for cleanest CW note. C8 and C9 are 365 pF and dual-365 pF (paralleled) tuning capacitors. LI is 35 turns of #24 enamelled wire on a 1 plastic tube. FT-243 crystals....
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This 49-MHz FM transmitter consists of an audio amplifier, a low-pass filter, three RF stages, and a regulated-dc power supply. The output is about 16 mW into a 50- load. This transmitter can be used in many 49-MHz applications, such as in a baby monitor,....
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This circuit was described in a recent edition of an amateur radio magazine. It allows operation in the 160- to 190-kHz band with up to 1 W (license free) in any mode (CW/SSB/FM, etc.) It consists of a receiving converter for 5 kHz to 450 kHz and a....
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A DSB transmitter is much cheaper to build than an SSB transmitter because no filter or phasing networks are required. This circuit produces up to 1-W output on the 10-meter band. The frequency 28.322 MHz is used, which is a commonly available clock....
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The simplicity of this transmitter compared to its very high performance makes it very interesting. Its output power is about 30 W and its range under normal conditions, with proper antenna and handling, reaches 30 km. The oscillator is the PL 84 which....
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Figure 1 shows the block diagram of a direct conversion RF receiver—the receiver demodulates an RF carrier directly into a baseband signal without an intermediate frequency down-conversion (a zero IF receiver). The antenna, shared by both the transmitter and....
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The F — V input frequency is locked to the V — F output because the LTClG43's clock is common to both sections. The F — V's reference is used as one input of the multiplier, while the V — F furnishes the other.
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The alarm plugs into the earphone jack on a receiver. Then when a signal (normally fed to the headphones) is detected and applied to the gate of SCR1, it conducts, sounding whatever alarm is connected to SOI. The signaling device can be an audible alarm or a....
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This circuit provides interferenced rejection for the CW operator. The 567 phase-locked loop is configured to respond to tones from 500 to 1100 Hz. The Schmitt trigger reduces the weighting effect caused by the output of the PLL remaining low after removal....
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High quality, noise free, wireless FM transmitter/receiver operates over standard power lines. Complete system is suitable for high-quality transmission of speech or music, and will operate from any ac outlet anywhere on a one-acre home site. Frequency....
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60 kHz transformer consists of a 18 x 11mm ungapped pot core (Siemens, Fer-rocube, etc), utilizing magnetics incorporated type "F" material wound with SOV2 turns of No5 wire for the secondary and turns for the primary..
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This circuit will double low-level signals with low distortion. The value of C should be chosen for low reactance at the operating frequency. Signal level at the carrier input must be less than 25 mV peak to maintain operation in the linear region of the....
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This converter allows coverage from 25 kHz up to 500 kHz. Use short coax from the converter to receiver antenna input..
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The trip point is set half way between the supplies by Rl and R2; R3 provides over 200 mV of hysteresis to increase noise immunity. Maximum frequency of operation is about 300 kHz. If response to TTL levels is desired, change R2 to 39 K..
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This converter uses a low-pass filter instead of the usual tuned circuit so the only tuning required is with the receiver. The dual-gate MOSFET and FET used in the mixer and oscillator aren"t critical. Any crystal having a frequency compatible with the....
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The decision to use either AM, narrowband FM Oess than 15kHz), or wideband FM (greater than 30 kHz) depends on the application. For the transmission of music, FM is better because it has greater noise immunity. For speech or other noncritical applications,....
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Input signals from the power line are coupled through C23 and R19 to the input filter network. C23 must be rated at 600 volts. Switch 52 is used as an attenuator. Components C2 through C7, L1 through L3, R1, and R20 form a triple-tuned bandpass filter....
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The AM Tuned Radio Frequency (TRF) receiver, has a sensitivity of about 1 m V at tbe input for an audio output of "iz W. Capacitor C22 couples audio signals from the power line to the PC board-it must be rated at 600 Vdc. R8 will cause F1 to blow, if C22....
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In the 100-kHz application from left to right, the coupling network feeds into the receiver ~section on the bottom of the chip. (The external components are summarized later.) The receive data output is pulled up via RPuLL ~ 10 K!l. A minimum current of 10....
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Among the signals below 550 kHz are maritime mobile, distress, radio beacons, aircraft weather, European Longwave-AM broadcast, and point-to-point communications. The low-frequency converter converts the 10 to 500kHz LW range to a 1010 to 1550kHz MW range,....
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The unit consists of rlamplifier Q1, local oscillatorQ2, and mixer Q3. The two bands are covered without a bandswitch by using an i-f or 3.5 MHz. The oscillator range is 7.5 to 14.5 MHz. Incoming signals from 4 to 11 MHz are mixed with the oscillator to....
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The NE602, U1, contains oscillator and mixer stages. The mixer combines the oscillator signal with the input rf signal to produce signals whose frequencies are the sum and difference of the input frequencies. For example, a 7.5-MHz signal is picked up by....
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This receiver is capable of better than 1.5 p, VIHF sensitivity and uses MOSFET front-end circuitry with varactors to eliminate conventional bulky tuning capacitors. It also features high dynamic range, ceramic i-f filters requiring no alignment, and a....
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The local oscillator is crystal-controlled and the i-f swing is hardly compressed. The deviation of the transmitted carrier frequency, because of modulation, must therefore be limited to prevent severe distortion of the demodulated audio signal. The....
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The various signal frequencies are obtained for an incoming carrier centered at 49.86 MHz. The receiver employs double conversion, with i-fs at 10.7 MHz and 455kHz. Ceramic filters are used in both i-fs for selectivity and reduced"coil count. A quadrature....
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This circuit is configured for the 80m band. The 365-pF, broadcast-band variable capacitor should have a vernier drive with a six-to-one ratio, which makes tuning easier by separating the stations on the dial. A good antenna and ground are also....
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When digital data is transmitted over long lines (longer than 1 meter), proper transfer is often disturbed by the parasitic effects of ground level shifts and ground loops, as well as by extraneous noise picked up along the way. An optocoupler, such as the....
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An NE567 tone decoder, tuned to the transceiver"s CW offset frequency, ensures that the transceiver will be tran..
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This oscillator-driver produces a deafening sound of about 3 kHz, modulated with a 10-Hz warble. BZ1 is a Matsushita EFB-RP3..
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This circuit will produce over +10 dBm in the 1800-3 000-MHz range. Drive power is 7 dBm in the 900-to-l 500-MHz r..
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This circuit will generate a linear sawtooth between 30 Hz and 3 000 Hz. Ql is a constant-current s..
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In this circuit, Ul is a frequency converter that feeds the 455-kHz IF stage U2 and detector..
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The RF signal is passed from the antenna through CI to the tuned circuit made up of LI and C2. One end of L2 feeds th..
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The transceiver mixer and carrier oscillator in the band-imaging (7- and 14-MHz) CW transceiver. Careful selection of ..
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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....
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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....
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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...
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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...
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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.....
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This circuit is designed to work at UHF frequencies in the range 450-800MHz. It has a gain of around 10dB and is suitable for boosting weak TV signals. The circuit is shown below...
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This project is a construction of a VHF-UHF linear amplifier that can work at frequencies from 47MHz to 740MHz. It can be used as a final output stage of any transmitter working between these frequencies. It use the BFQ34 NPN a 4GHz wide-band transistor with....
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This amplifier is intended for amplifying low signals from oscillators in the FM band. It does not have frequency regulators with variable capacitors and coils, it has a wide range and moderate power capable of driving several linear amplifiers. The whole....
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This circuit is an amplifier for small transmitters operating in the UHF band, specifically in the 450-800MHz range. The amplifier works in class A and we used the well-known Philips BLW33 transistor for its manufacture. The construction, although simple,....
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The logic input is applied to opto-isolators Ul and U2 with, respectively, npn and pnp emitter follower outputs. Dc balance is adjusted by potentiometer R2. The emitter followers drive the gates of Ql and Q2, the complementary TMOS pairs. With a ±12 V....
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The circuit works from dc to 50 MHz and will deliver pulses as short as 10 ns. It is driven by a TTL signal through a 740S00 quad Schottky NAND gate, ICA through ICD. Transistor Ql, wired as a common-emitter amplifier, drives transistor Q2, a simple emitter....
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The amplifier provides a total power gain of about 25 dB, and the construction technique allows the use of inexpensive components throughout. The MRF476 is specified as a 3 watt device and the MRF475 has an output power of 12 watts. Both are extremely....
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This amplifier operates from a 28 Vdc supply. It has a typical gain of 12 dB, and can survive operation into a 30:1 VSWR load at any phase angle with no damage. This means that with input power held constant at the level that provides 125 watts output, the....