This experiment was done when I was a SWL & also studying for RAE in year 2000. This circuit was based on a FM radio originally made for  receiving FM broadcast stations. I modified its RF coil & local OSC coil & removed BPF at the front end & replaced a 50 ohms matching part to suitable 50 ohms antennas. Also AM section was disabled in the receiver. 

As this design is a single conversation receiver & trying to receive narrow band FM signals, it might be difficult to lock the tuning between 144 MHz & 146MHz. But once locked it receives 2M signals nicely. 

A homebrewed ground plane antenna was used during the experiment to receive a local repeater on 145.625 MHz. Later connected a homebrewed  8 element beam with a folded dipole antenna. Both worked with this receiver without any problems.

KA 22426

This IC is all-in-one chip made to receive FM broadcast stations. This Integrated chip has a FM front end RF AMP, Local OSC , 10.7 MHz IF section, FM quadrature detector & an AF power amplifier.   Additionally it has tuning meter, FM AFC & Also a variable capacitance diode for  fine tunings arrangement. 

  #    Capacitors             #    Resistors    

  1       C1    220  µF        R1    10k

  2       C2     0.1  µF        R2    100 ?

  3       C3    470  µF        R3    100K

  4       C4      10  µF        R4    220 ?

  5       C5    0.47 µF           

  6       C6  0.022 µF        Ceramic filter    10.7 MHz

  7       C7       10 µF         Crystal    10.7 MHz

  8       C8      4.7 µF           

  9       C9    0.01 µF        Tuning capacitor    15PF - 30PF

10    C10        10 µF        Speaker     4 ? / 0.25W

11    C11       4.7 µF           

12    C12           1PF        IC   

13    C13     0.01 µF        KA22426   

14    C14        10 µF           

15    C15        22 PF           

16    C16         22PF           

17    C17         22PF           

18    C18         18PF           

After I got  the radio amateur license, this modified radio was gifted to a friend of mine who is an another SWL & therefore I don't have it now to publish photos with this article. Also I didn't prepare a  PCB pattern, I only modified a working FM radio.

My next experiment with KA22426.

First a PCB pattern will be designed. As this chip has a  variable capacitance diode , an AFC block. So a manual variable capacitance diode tuning system will be added using the internal very cap diode. Also will add a tunings meter system to indicate signal strength an S meter level. All modifications will be published here when the experiment will be completed.