Dilshan R Jayakody’s Web Log

In this project, we extend the shortwave superheterodyne receiver we developed a few years ago . Like the previous design, this receiver operates on the traditional superheterodyne principle.  In this upgrade, we enhanced the local oscillator with Si5351 clock generator module and Arduino control circuit. Compared to the old design, this new receiver uses an improved version of an intermediate frequency amplifier with 3 I.F transformers. In this new design, we divide this receiver into several blocks, which include, mixer with a detector, a local oscillator, and an I.F amplifier. The I.F amplifier builds into one PCB. The filter stage, mixer, and detector stages place in another PCB. Prototype version of 455kHz I.F amplifier. In this prototype build, the Si5351 clock generator drives using an Arduino Uno board. With the given sketch, the user can tune and switch the shortwave meter bands using a rotary encoder. The supplied sketch support clock generation from 5205kHz (tuner f...

Recently I got an ICOM IC-R71A receiver from my friend. ICOM IC-R71A is a multi-mode quadruple superheterodyne receiver with the frequency range from 100kHz to 30MHz. When it comes to my workshop it's completely dead but outer casing and front panels are in really good condition. Before troubleshooting the receiver, I download both user manual and service manual from the internet. As like all ICOM products this receiver also comes with very detailed user manual and service manual. Restored ICOM IC-R71A receiver As I observed this receiver consist of many PCBs which including: Mainboard Front boards (altogether 7 boards, which including 1 mainboard known and matrix board and 6 small PCBs) PLL board RF board Logic board and RAM board Power supply board In addition to above boards, there are some previsions in this chassis to install other optional boards such as FM board. After observing the power supply board, I notice a couple of dry joints in the rectifi...

This is two transistors and two IF transformer based superheterodyne receiver which is designed to receive 13m to 41m bands. With quite good external antenna this receiver performs similarly to the commercially available shortwave receiver and its audio quality is at a very satisfactory level. Prototype version of two transistor superheterodyne shortwave receiver. This receiver can be constructing on PCB, breadboard or commonly available veroboard or stripboard. For tuning use Polyvaricon or air variable capacitor. For precision tuning, connect small trimmer capacitor with parallel to variable capacitor’s gangs or use mechanical wheel assembly with the variable capacitor. This receiver is designed to work with 9V regulated power supply and it requires an external AF amplifier to drive the headphone or speaker. In our testing, we use a TDA2050 audio power amplifier with this receiver. With small wire antenna, this receiver is capable to receive most of the stations which in...