How to optimise the Air Band Radio Tuning Circuit?

[lsk2141]

Dear Sir,

This Air Band Radio Kit R20 was completed successfully.

The FM is audible but at in tune optimally. The Air Band cannnot even pick up the strongest signal.

I suspected the tuning circuit is not correctly match with the optimal resonance frequency, are capacitor value of C21-C24 AND C30-C31 play a role in optimising the signal tuning?

Which capacitor and what value of the trimmer capacitor i must replace for me to serach for the strongest and clearest signal?

Thank you.

 

[BigBoss]

Not filter components but also Band Switches, PCB , Components' Quality and Tolerances etc. play important role overall Receiver Sensitivity.
I have looked at a glance the application schematic of the IC, the supplied schematic has been heavily modified compare to.
If you want listen to Air Band, you have to design your own Receiver instead of using specific IC.
Not very difficult. All you have to do is to find the right components such as PLL+Oscillator, Double Balanced Mixer and FM Demodulator.

 

[lsk2141]

Dear Sir,

Thanks for your reply.

I will try to construct a few Regenerative Air Band Receiver using circuits shared by other enthusiast instead of buying kits. These circuits has minimal ICs except the LM386 amplifier.
I am not a professional in this area, will be relying much on good circuits designed by others.
Hope that this would work out much better than the current one.

Best Regards

Low

 

[Externet]

Airband 108 to 137 MHz works in amplitude modulation AM, not FM. If you are trying to hear communications on it, you must use the correct demodulator.