FM receiver modification (how low can u go?)

[zachtheterrible]

I'm trying to perfect a 3volt transmitter. I was getting SOO sick of competing with other radio stations, so i tried to modify my receiver to receive below 88-108 MHZ. I did this by connecting a capacitor in parallel with the tuning capacitor. The trouble is, i cannot hear my transmitter below 88 MHZ, in fact, i can't hear anything. I did this same thing with another radio and was able to hear tv stations and other noises, but with this radio, all that i hear is that FM hiss.

My question is this: The receiver consists of three chips and a bunch of components. Is it normal for radio chips to limit how low i can go?

 

[panic mode]

well if it's superhet, you would have to make changes in two places: input circuit and oscillator and this has to be done carefully so you get same difference (10.7MHz). If not, you will get something pretty much as you describe.

 

[zachtheterrible]

what is the input circuit?

 

[zachtheterrible]

what is the input circuit? and is there any way of telling if it is a superhet? its just a little piece of junk radio with an earphone jack.

 

[Russlk]

If the tuning capacitor has only one section, then it is tuning the oscillator and the other circuits are fixed. If you are not far below 88 mHz, it should work.

 

[zachtheterrible]

hmm, very strange, it definitely doesn't work. ive tried tons of different value caps, 6,10,15,22,33,39. i even plugged in a 5-65pf cap and that didnt work. ah well, i guess its a lost cause with this receiver.