There is no doubt that this small power amp packs a punch. It is capable of delivering a healthy 200 W into 4 Ω. Into 8 Ω it can still output 125 W. These large power outputs are made possible through the use of Darlington transistors made by Sanken, the SAP16N and its opposite number, the SAP16P (in our prototype we used their predecessors, the SAP15N and P, because the SAP16 versions were not available at that time). These power transistors have an emitter resistor built in, as well as a diode for temperature compensation. Because of this, the whole emitter follower stage has just two components.

Read the rest of this Compact 200W amplifier

In 1896, Marconi successfully covered a distance of about 3 km using electromagnetic waves. A little later, he established radio contact across water between Lavernock Point, South Wales and Flat Holm Island. The transmitter consisted of a spark inductor coupled to a dipole antenna.

A clap switch circuit is a classic beginner’s project. Equipment can be switched on and off by just clapping your hands. Add a tiny microcontroller and you can easily build-in some more useful features.
The microcontroller in this circuit makes it a simple job to add some useful features that are not seen on other clap switch designs:

RFSim99 is a freeware software that can help you in RF simulation, in your projects, especially if you are trying to design radio filters.

RFSim99 works with S-parameters. This means that not only will it simulate and analyse circuits built out of its internal library of components, but that it can accommodate any circuit block or stage for which these are known.