This is simple radio receiver project which is capable to receive aviation radio voice signals which are transmit between 118MHz to 138MHz in AM (A3E). We got initial idea of this project by reading one of Sverre Holm’s (LA3ZA) article, which is titled as "How to make a very cheap VHF receiver". Like LA3ZA’s original article this project is also based on Samsung’s KA22429 FM radio receiver IC.

Prototype of KA22429 Airband receiver
Prototype of KA22429 Airband receiver

KA22429 is low voltage FM radio receiver system developed by Samsung for portable radio receivers and as described by Holm’s it can push into VHF region by changing few values in its original circuit. In this project we redesign the schematic and PCB with some of those changes and now it can directly tune into aviation band with minimum number of adjustments.

The critical components in this tuner are L1, L2 inductors and variable tuning capacitor. For both L1 and L2, wind 6 turns of 24 S.W.G copper wire on 5mm bobbin. Both L1 and L2 need to be air core and length should be around 25mm - 30mm.

For variable tuning capacitor use standard tuning condenser which is available in commercial FM radio receivers. More details of inductors and tuning capacitor are available in following figures.

ka22429_inductor_details.png
L1 and L2 inductor winding parameters

ka22429_wiring_details.png
PCB external connections diagram

The dimension of PCB of this receiver is 70mm × 45mm and all the components except KA22429 are standard through-hole type.

For the optimal results we recommended to use high gain audio power amplifier and good external antenna with this receiver. During prototyping / testing, we drive this system with 5V DC power supply and also connect this receiver to TDA2050 AF power amplifier. At our testing we got very successful results on 124.900MHz (Colombo Airways Center), 119.100MHz (Colombo/ Ratmalana Approach) and 118.100MHz (Colombo/ Ratmalana Tower). The recorded sample on 124.900MHz using this receiver is available in here.

KA22429 testing setup with 5V PSU and AF power amplifier.
KA22429 testing setup with 5V PSU and AF power amplifier.

By changing the C14 this receiver can tune into more deep frequencies which including 2m amateur radio band and VHF low frequency TV signals.

Project Related Downloads


Schematics, PCB design and wiring diagrams of VHF Aircraft radio communication receiver.

References


How to make a very cheap VHF receiver - Sverre Holm LA3ZA
KA22429 - FM Radio
32W Hi-Fi Audio Power Amplifier using TDA2050
5V 5A Bench Power Supply