M radio is almost complete

[mstechca]

The circuit I am using is shown in the "I can't believe my FM radio is going haywire again!" thread of this forum.

I have knocked my radio problems down to just ONE diode. It is the diode
(highlighted in teal) that goes to the base of the transistor where the higher value capacitor is connected to as well. Using different diodes gives different results.

Here are the diodes I have tried, and I got the following results.

1A, 800V silicon diode - Hums! Can't hear anything but a loud HUM!
21ma, 12V zener diode - This was the best diode. I can hear the station well.
41ma, 6.?V diode - Same as above, but with background hum.
21ma, 8.2V zener diode - The station was mixed with FM noise.
21ma, 7.5V zener diode - I only receive FM noise!


So what IS the best diode to use? It may look like I'll need to buy another package.

 

[Scubasteve]

Hey,

Why are you just plugging in random diodes?, you do not learn anything from this. My advice to you is, "Understand how the circuit works and why the diode is there", then you will know what is required. Is it a detector diode, mixer diode, reverse current protection diode, clipping diode?

Steve