Small Circuits Revival – Episode 12

Last week we tempted you with a preview of the reflex receiver; in this instalment we will continue to develop this idea.

In the previous instalment we looked at the simplest possible radio receiver: the diode receiver. And in order to tickle a little bit more sound volume out of it, we added a small amplifier stage. Nevertheless, such a diode receiver has its disadvantages. Here we will try to do something about that.

In the past, radio had something ‘magical’, and that is not all that surprising: you solder a few ‘unsightly’ components together, tie an antenna and headphones to it and... it is unbelievable, but through the noise, voices and music can be heard!

Many (beginning) electronics enthusiasts shy away from building radio receiver projects – frequencies are too high, capacitor black magic, scary inductors... The reality of a receiver that actually performs very well using only a handful of standard parts is demonstrated by this circuit.

The WSPR (Weak Signal Propagation Reporter, pronounced ‘whisper’) radio transmission technique was developed to enable considerable distances to be spanned using low power and minimum bandwidth. This article shows how you too can transmit WSPR reports using the Elektor SDR Shield and free software.

This is a submission from Rutronik on the compact wireless transceiver module TCM 515. This module is suitable for systems such as transceiver gateways, actuators and controllers that communicate based on the EnOcean radio standard in the sub-GHz band. It provides reduced power consumption, smaller size and a lower purchase price compared to the previous generation TCM 310, which is still available.

For aircraft enthusiasts and in particular plane spotters, it’s always interesting to listen to communications between aircraft and control towers. This receiver makes it easy to listen to all traffic in the civil aviation band. It is easy to build, has only one hardware adjustment, and can even be controlled from a PC with a USB port.

A new wireless transceiver invented by electrical engineers at the University of California, Irvine, boosts radio frequencies into 100-gigahertz territory, quadrupling the speed of the upcoming 5G wireless communications standard.

Author Burkhard Kainka’s inspiring Foreword in the book I’m reviewing here has important clues as to why software defined radio (SDR) is a hit not only among existing radio amateurs. SDR has proven to be a great promotion tool for the declining radio hobby in general. Since the tuning and decoding of shortwave radio signals is now done with a minimum of hardware and powerful (free) software, it’s easy to see why newcomers to the radio hobby and others with “DC minds” or with “deep fears of RF” have been totally captured by the concept of SDR.

How do you receive RF signals like FM radio or traditional broadcast television? Since this is Elektor it’s much more interesting to use a dipole antenna instead of a dedicated wire connection like cable or the Internet. A dipole antenna works by generating small amounts of current in the presence of an electric RF field which is then sent to the receiver using two-wire conductor called twin lead cable which is a balanced antenna cable. Let’s take a look at what makes this cable so special.