This project has been developed together with some other OMs (in particular Marco IW1DGG) in our local radio club. When we started looking at a simple transmitter providing sufficient power to exice the local ATV repeater we did not find anything simple to build and with components easy to find. At that time there was on the market one transmitter
Click here to download the full size of the above Circuit.
based on SMDs components and using a Mitsubishi hybrid power amplifier (M67715) no more available almost everywhere. Looking on internet we found a simple transmitter based on through-hole mount components only and providing 50mW RF power. It was presented at the ATV Meeting in Treviso in 2001 and you can find it here (in italian ony), on the ARI Vittorio Veneto web site. We have only slightly modified this transmitter adding a power amplifier stage based on a BFG35 (or BFG135) providing about 0. 5W output RF power, which is sufficient to operate through repeaters and to perform short distance (tens of km) direct QSOs. This is the electrical diagram of the complete circuit as we modified. You can identify the video input section with the A-V mixer in the upper-left part of the diagram, the audio section in the lower-left part of the diagram (around the TL081), the PLL and low power stage in the center of the diagram (composed by the PIC, the TSA5511, the BFW91 and the first BFR96) and the power stage on the upper-right part of the diagram (composed by the second BFR96 and the BFG135). The PCB that we have realised is based on the ARI Vittorio Veneto design and consists of a simple two layer board. All components are "big size" (no SMD) except for the RF varicap diode. Some of them have to be soldered directly on the component side, but the majority is mounted in a standard way, i. e. via through-holes soldered on the...
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: