Simple FM radio receiver for the 88-110 MHZ band Schematic and demo with a TBA 120 IF Amp.

The video shows a simple Superheterodyne Radio circuit made to receive FM radio signals between (in principle) 88 MHz and 110 MHz.



Earlier videos are here:
TBA 120 IF Chip used with 10.7 MHZ or (450-470) KC coil filters
https://youtu.be/9RZguOLtRoE
VLOG first thoughts about an IF Amplifier (for a radio circuit)
https://youtu.be/4JXd7E9nA5U
80-110 MHZ oscillator made Manhattan style
https://youtu.be/7J_ppNyJWbU



Please note: due to the limited frequency band that the VFO can generate in this (here demonstrated) case (say in a 3 MHZ wide bandwidth in the total FM band, say between 103 and 106 MHz) the circuit only receives (in this case and in the Netherlands) 3 FM broadcast stations.

That can be changed somewhat by giving the tank circuit of the VFO another parallel capacitor, so that it strays out in another frequency bandwidth (with the 1N5408’s diodes always say 3 MHZ wide).

Has also to do with the capacitance of the used diodes that determine the frequency/tuning. I used normal Si diodes, the IN5408’s, say not real varactor diodes/varicaps. Real varicaps (varactors) have the property of a quite high capacitive variation on their barrier layer when a tuning voltage is added. More info in the video and the schematics in the video.

Perhaps with real “varicaps” (varactor diodes, say varying between 10 pF and 80 pF) it will be possible to cover all frequencies (read: radio stations) between (say) 88 MHZ and (say) 110 MHz.



This circuit in the video only shows (working…. always the aim of my YT Channel) principles with which you can experiment further.
Circuit cannot be made on a (say) standard breadboard, it “must” be made in the way that is showed here: copper clad board, shielding (with tin plates, vertical) between all the HF and IF stages, no “leakage” of HF signals over the power supply lead, so good “decoupling” of each (transistor) or “chip” stage, etc, etc. Say: Manhattan HF style. Check everything with the oscilloscope (60 MHZ-200 MHZ) if possible.


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