Short-wave listeners often are not able to, or allowed to, install a long-wire antenna or other large dimension antenna in or around the home. In such cases, the present active antenna, intended for the frequency range 3 30 MHz, may be found useful. The author used a 1-metre long rod or brass tube with a diameter of 2 6 mm. The circuit consist
Click here to download the full size of the above Circuit.
s of two parts, one to be located close to the antenna, while the other should be placed in the associated power supply of the receiver. The two sections may be connected by a coaxial cable of up to 20 m long without causing any discernible attenuation. The antenna signal is pre-amplified by a two-stage combination, T1-T3. The main amplification is provided by the input transformer, formed by L3, L4, and L5, in the receiver section. This is followed by a switch that enables the frequency range to be selected (3 10 MHz in position LOW, and 9 30 MHz in position HIGH). The signal strength may be adjusted to suit the receiver with potentiometer P1. The active antenna is readily constructed with the aid of the two printed circuit boards shown. Since we are concerned with only relatively low radio frequencies, the choice of components is not too crucial. Various types of FET may be used: BF245, BF246, BF256, or the SMD variants of these, but do mind their connections! The same applies for the transistors: BFW16, BFY90, BFR91, BFR96; any of these will do. A few hints for readers who conduct their own experiments. A lower value of capacitor C1 results in a somewhat looser coupling to the antenna, but also in lower signal strength. It may be worthwhile to replace the capacitor with a variable type. Inductor L6 ensures that the output voltage at higher frequencies (30 MHz) is not much higher than at lower frequencies (3 MHz). This is...
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: