Dilshan R Jayakody’s Web Log

This project focuses on a simple yet powerful FM stereo tuner module. The core component of the module is RDA5807M , a single-chip broadcast FM stereo tuner that has gained popularity among designers in recent years due to its high level of integration. This integration significantly reduces the need for external components, simplifying circuit design. The RDA5807M supports a wide FM band, covering frequencies from 50MHz to 115MHz, making it adaptable to global FM standards. Additionally, its use of a low-IF digital architecture streamlines the design process by requiring fewer external parts. The inclusion of an AGC (automatic gain control) feature ensures consistent signal reception, even in environments with fluctuating signal strengths. FM stereo receiver module with seven segment module. The chip's digital stereo decoding capabilities deliver high-quality audio output, providing a rich stereo sound experience. Moreover, the energy efficiency of the RDA5807M makes it suitable...

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...

The QN8035 is a stereo FM radio receiver launched by the Quintic Corporation . Compared to other popular digital FM tuners ( RDA5807 , TEA5767 , etc.), this tuner does not seem to be as popular among the DIY community. As we have seen, the biggest problem with this IC is the lack of information. During our initial search, we came across some details about this IC. Much of that information was confined to a product datasheet and a few undocumented GIT repositories. Based on the information we found on the internet, we concluded that Quintic was no longer in business. According to the NXP website , it stated that Quintic Corporation was acquired by NXP in 2015.  Although the Quintic is no longer in business, the QN8035 IC can still be purchase at a low price from online stores. In addition, we found several FM radio kits manufactured using this IC in online stores. Due to the lack of information, I decided to explore this IC to understand its functionality and limitations. In t...

This is an RDA5807M based FM stereo radio module. This module is designed to replace old, low-voltage, analog FM stereo radio receiver modules. Like many digital receivers, this module also got auto scanning, station memory, and digital volume control. This module can driver using 5V to 9V DC power source. FM stereo receiver module with seven-segment display unit. The frequency range of the receiver is 88MHz to 108MHz. The auto scanner of this module can tune the receiver with 25kHz increments in up and down directions. The memory manager available with the current firmware can hold up to 10 stations in MCU EEPROM. Bottom side of the receiver module The dimensions of this module are 72.85mm × 32.0mm. With the seven-segment display, the depth of the assembled module is 37.5mm. AF output power of this module is not sufficient to handle the pair of speakers. To drive speakers, this module needs to pair with a stereo AF power amplifier kit/module .  This is an open-source hardware pro...

This is simple, but very high-quality CXA1191S based FM radio receiver system. In this design, we use Sony CXA1191S as FM tuner and TDA2003 as an audio amplifier. This receiver system is designed to work with 12V DC power source and it delivers approximately 6W audio output power (with 4Ω speaker load). The core component of this receiver system is CXA1191 FM radio IC, and for this design, we use 30 pin version of CXA1191 (which is known as CXA1191S) because it's commonly available in electronic component shops (and in eBay ). Due to less availability of IF transformers we did not use any IF transformers in this design and only the FM section is used in the IC. (AM section of the IC is ignored due to unavailability of broadcasting stations in here in Sri Lanka ) A prototype version of CXA1191S FM radio receiver. Compare with most of the FM radio ICs this CXA1191S receiver offer very good selectivity and higher sensitivity. After adjusting (all inductors and trimmers) we w...

TX-7700 is AM/FM stereo tuner manufactured by Pioneer in around 1975 - 1980. This is a basic tuner system which is specifically designed for " rack style " stereo systems. Compare with other tuner systems this tuner is not very popular and very limited information is available on the internet about this model. This tuner is mainly built around HA1138 AM radio receiver, HA1156 stereo decoder and PA3001 (HA11225) FM IF amplifier IC. The TX-7700 which I got is manufactured for Japan and because of that it is designed to work with 100V AC and frequency range is limited to 76MHz to 90MHz. In this quick post, we demonstrate how to tune this stereo receiver to 88MHz to 108MHz by without modifying the circuit(s) of the tuner. In this tuner, the main component which needs to adjust is 5 turn inductor located in FM front end circuit (refer A in below photograph). The frequency range of the tuner can be adjusted by changing the spacings of this inductor. If tuning is getting dif...

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...

Recently I got vintage Eddystone EC10 MK1 communication receiver from friend of mine and it is completely dead when it comes to me. EC10 MK1 is one of Eddystone's very early solid state communications receivers and it use 10 PNP Germanium transistors. This receiver cover 550 kHz to 30 MHz and come up with BFO for CW and SSB receptions. Restored EC10 MK1 HF communication receiver The main problems which I noticed in my EC10 is corroded wires, components and PCB. I did restoration step-by-step and most of the steps are listed in my qsl.net page . Other than repairing, this article covers details of power supply which I integrated into EC10 communication receiver. The schematics and photographs are available at the same article . After repairing and above changes EC10 starts to work again and with some external antenna is performs quiet well. Most of the times I use this receiver to listen to 40m 4S7RS net on 7060kHz.