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 its 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)

Prototype version of CXA1191S FM radio receiver.
Prototype version of CXA1191S FM radio receiver.

Construction of this receiver system is quiet straightforward and it uses commonly available through-hole type electronic components. For C3 use 4 gang PVC variable capacitor. In our prototype we use Chinese variable capacitor for C4 and it can vary from 3.5pF - 23.5pF. In our design both C4 and C5 capacitors are calculated based on above variable capacitor specifications.

L1, L2 and L3 are home made air core inductors. All these inductors are wind using 22 S.W.G enameled copper wire on 5mm ⌀core. All the inductor winding details are listed in below table:

Coil
Diameter
Wire
Turns
L1
5mm
22 S.W.G
2 ¾
L2
5mm
22 S.W.G
3 ¾
L3
5mm
22 S.W.G
2 ¾

For XTAL1 use 10.75MHz ceramic discriminator and use 10.75MHz ceramic resonator for XF1. While at assembling make sure that pin 1 of XF1 is connected to R4. In PCB, SV1 connector is used to attach 50K (Log) potentiometer to control volume of the power amplifier. To get good audio output connect 6 or 8 inch full range, 4Ω/8Ω speaker into SL1.

Compare with most of the FM radio ICs this CXA1191S receiver offer very good selectivity and higher sensitivity. After tuning (all inductors and trimmers) we were able to get all FM stations from this receiver with 15cm wire antenna.

PCB is the most recommended way to construct this circuit. Given PCB design is 115mm × 61mm and all PCB and schematic diagrams are available to download in below.

Project Related Downloads


Schematics and PCB design of CXA1191S FM radio receiver

References


CXA1191S - FM radio
TDA2003 - 10W car radio audio amplifier
78L05 - 3 terminal low current fixed 5V voltage regulator