DIY Portable FM Radio (Part 2) Potentiometer Tuning

I continue my post here about making the FM radio front end. The AFC out from it need to be connect to the FM modulator. In this project I using the very popular IC, it is LA1260. I also using the common potentiometer for radio frequency tuning instead of variable capacitor just like many commercial radio have.

I tell you a story behind this project. I want a radio after see the front end board as describes on the part 1. I looking around and find the Sony ICF-P36 is very tempting. Unfortunately after I test the unit, it is not impress me in term of sound quality and the FM radio reception. So I better built it for myself:)

This is the full schematic of the FM modulator using LA1260. It is very common schematic but the different with others FM radio is on the tuning point. I using potentiometer  to swing the voltage on the FM front end thus it control the FM frequency reception.

You also see the AFC input has 2 point in this modulator. One before the CF on IC pin 1 and the other at the radio analog output after the 1 mega ohm resistor.

I continue the components placement after the front end circuit.

I attach the IFT body to ground by a single wire.

And this is the final layout. The FM front end and the modulator has been connected each other. In this step, this radio is now working properly.

You can attach the output from IC pin 8 to an earphone. You will hear the sound from it and it is useful for checking the radio is working or not before going to the next step.

I using the ALPS green potentiometer for this frequency tuning. I also make the small adjustment on the IFT for clearer radio reception. The next step will be adding a small amplifier circuit that capable for a 3 volt supply.

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