I have a radio question

[mstechca]

I have just about completed my homemade FM radio, and it incorporates an amplifier similar to that shown below:

**broken link removed**

If you don't see a picture, go to: **broken link removed**

Anyways, the only problem left is the maximum volume. When it is low, there is practically no distortion. HOWEVER, as soon as I connected a 5nF capacitor between tr1's base and emitter, the volume has doubled. Once I added a 2.7nF capacitor between the base and collector of Tr3, the volume has increased another 50%, but now I am hearing unwanted oscillation.

Changing the stations seems to have no effect. Is there a way I can obtain lots of volume without all the distortion? do I need to lower my input current or voltage?

 

[Nigel Goodwin]

I have just about completed my homemade FM radio, and it incorporates an amplifier similar to that shown below:

**broken link removed**

If you don't see a picture, go to: **broken link removed**

Anyways, the only problem left is the maximum volume. When it is low, there is practically no distortion. HOWEVER, as soon as I connected a 5nF capacitor between tr1's base and emitter, the volume has doubled. Once I added a 2.7nF capacitor between the base and collector of Tr3, the volume has increased another 50%, but now I am hearing unwanted oscillation.

I'm somewhat surprised that you should start randomly adding capacitors in an effort to improve the circuit?.

For a start I would suggested using the circuit below the one you did, the bootstrapping will improve the circuit a great deal - although it still isn't a very good design, probably actually not meant to be one?.

 

[Roff]

I have just about completed my homemade FM radio, and it incorporates an amplifier similar to that shown below:

**broken link removed**

If you don't see a picture, go to: **broken link removed**

Anyways, the only problem left is the maximum volume. When it is low, there is practically no distortion. HOWEVER, as soon as I connected a 5nF capacitor between tr1's base and emitter, the volume has doubled. Once I added a 2.7nF capacitor between the base and collector of Tr3, the volume has increased another 50%, but now I am hearing unwanted oscillation.

Changing the stations seems to have no effect. Is there a way I can obtain lots of volume without all the distortion? do I need to lower my input current or voltage?

The schematic is almost worthless without component values. Post the values and the supply voltages, and also a schematic of the circuit that the input signal comes from.

 

[Russlk]

The 5 nF cap no doubt increased the audio by filtering out some of the RF. A better filter would have a series resistor of 3K3 ohms before the cap.

 

[TheOne]

Here is the page **broken link removed**

Why do you want to connect capacitors between base and emitter/collector?