TR1 (BC547) is an inverted Hartley oscillator which based upon an inductor fabricated on the PCB. This makes it megga-stable, and setable anywhere in the VHF FM band (76MHz to 119MHz) and the BB105 varicap makes it voltage tuneable over about 8MHz of that band. The inductor has one tapping for feedback and a second to feed an optional prescaler. TR2 is a buffer/amplifier and TR3 it the PA stage.
Click here to download the full size of the above Circuit.
A single CD4046 and crystal oscillator can be used as a very simple PLL frequency controller for this transmitter with the frequency being determined by the crystal. I used this technique with the V6 transmitter so you have circuits available to suit your needs.
The V7b acts as a simple 1.375MHz to 1.6875MHz external VCO for just about any "Single modulus" synthesiser, with MC (pin 2) = +5 volts. With MC=Gnd then it acts as a 1.354MHz to 1.662MHz VCO. The final TX output is 64 times the synth frequency with MC=+5v (65 with MC=Gnd). This means that it will operate with my simple CMOS synthesiser and give final frequency steps of 50KHz with the correct reference crystal (6.4MHz).
With a "Dual Modulus" synthesiser, such as the MC145152-2, then the V7b will form a dual modulus synthesiser and can be controlled in steps of typically 5KHz. Only problem is that the chip costs more than the complete simple CMOS synthesiser.
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.....
characters left: