The Frequency instability in VFO stage is a common problem. This is usually occurred in VFO`s due to low Q of the tank circuit, capacitors real value, power supply regulation, stray capacitance, lead inductances and over feed back levels etc. Few months back, I had discussed about VFOs and Oscillators with one of the veteran home brewer, he is
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a senior amateur licence holder than me and he is working as JE in communication filed. In that discussion, he told me that while oscillating the bi-polar transistor based VFOs, the first transistor emitter-base voltage should shows as negative volt and this Js an indication of healthy operation. He showed me a practical demo also. When I started my 7MHz, AM/SSB/CW RX project due to heavy compulsion from HAM`S and SWL`s. I started designing work on September 2004, the aim to release the circuits and the PCB on Adoor HAM `XPO 2004 on 21 st November. I strictly started the proper designing for the benefit of new license holders and SWL`s to get practice about systematic receiver assembling. During that period, while designing the 7 Mhz RX project, I discussed with VU2ARA, Arasu, about VFOs through Kodai VHF repeater. He strictly told that the first transistor emitter-base voltage must be a positive volt. Due to this positive and negative charge a lightning stroked my brain. VU2ARA never disclosed the exact principle about a positive voltage at emitter-base while oscillating and he forced me to find out myself. I could not get any information from anywhere including ARRL or from any other amateur radio based articles. I discussed with VU2ITI, Prof. T. K. Mani and he supported the statement of VU2ARA and reminded me that the first transistor is in class A` mode. Then I realised why the positive voltage should keep at E-B...
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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