VHF Circuits
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The material in this section shows how we built the Twist-Shift system for VHF using commonly available (and cheap) surplus land mobile VHF transceivers modified to operate on the 2-meter ham band. The radios we used were the 100-watt Motorola SyntorX model..... -
Phase-sensitive detectors usually take the difference between an input FM signal and the same signal after it has passed through a resonant circuit, or through a delay line. A 1N34 should work fine to detect 100MHz, but not all 1N34 diodes are made alike..... -
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You can cut away the 555 timer oscillator part and add your favorite microphone modulating circuit to transmit voice over to your tv set with a little tuning. Schematics in Schematics Depot were found on the internet and assumed to be in public domain..... -
This article provides conversion instructions for radio model # GE/MACOM MASTR-III Group 2 (150. 8-174 MHz) Repeater or Base, Combination Number SXS, to allow it to perform adequately in the 144-148 MHz range. Please be aware that this document is currently.... -
Developed as interface between General Instruments AY-3-8500-1 TV game chip and antenna terminal of TV set. Adjust C1 to frequency of unused channel to which receiver is set for playing games. Article gives all circuits but covers construction only in.... -
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.... -
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.... -
The TV transmitter introduced here can send audio and video signals of satellite television receivers, VCDs and video recorders in open circuit, and receives signals with open antennas. It is suitable for self-made programs of working units, schools, and.... -
This is a simple video transmitter that can transmit as far as 50 meters. This video transmitter can be used with the camera or other video sources. You can view them on VHF channel analog TV. Supply voltage to the video transmitter can use 9V battery..... -
Circuit`s Functions The frequency modulation FM transmitter which can be used in 76~90MHZ FM radio band, usually also it is called wireless microphone.It adopts signals via FM radio receiver.The signals can be transmitted in wireless means if we don`t use.... -
If you want to be independent of the local radio stations for testing VHF receivers, you need a frequency-modulated oscillator that covers the range of 89.5 to 108 MHz ? but building such an oscillator using discrete components is not that easy. Maxim now.... -
VHF overtone crystals can be difficult to use due to the many frequencies at which the crystal is perfectly happy to oscillate. A typical 100 MHz, 5th-overtone crystal will oscillate at approximately 20 MHz, 60 MHz, 100 MHz, and even 140 MHz, not to mention.... -
Finally I have found a use for a bunch of DIP-style RF relays I acquired in a grab-bag from a discount electronics shop some time ago. These babies are sealed totally, and rf shielded with low contact capacitance. Perfect for VHF frequencies. They are 12.... -
A typical circuit at 20 MHz is shown. The crystal, which has an internal series resistance RS, of 14 ©, oscillates at its third harmonic. The diode clamp D1 and D2 provides a constant amplitude control. The transistor operates continuously in a linear mode.... -
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The intelligent discussion of VHF systems requires a feel for VHF systems, and how VHF energy moves through a system. At VHF, wavelength is very short. Wavelength in feet is F/983. 6, a typical 150 MHz system would have a quarter wavelength of 19. 8 inches..... -
Replacing the front-end with a circuit that down-converts VHF signals in the 2m, 4m or 6m bands to HF signals that can be received in the RX`s "back-end" (which is essentially the Ensemble II RX). The parts provided in this kit permit the builder to select.... -
This stage begins at the VHF antenna. The incoming VHF RF signal is preamplified and filtered and presented as the "RF" signal to the ADE + Double Balanced Mixer (DBM). That mixer also accepts the Local Oscillator `s output (BEFORE the Quadrature Clock.... -
The RF stage of the receiver is based on a transistor VT1, this stage works as a mixer and a local oscillator and it works as a synchronous detector. A cable of the headphones works as an antenna. A signal received with this antenna is fed to the input.... -
The figure below shows a schematic diagram of a simple FM receiver. This receiver made with four transistors. The signal from the antenna through the trimmer capacitor C1 goes to the input of the first stage. This stage is a super-regenerative detector based....
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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