Dear Sir,

I am a new comer in this forum, I wish that I am posting to the right thread. Please excuse me if I am not.

I am doing an electronic project on Air Band Radio Receiver, I got the circuit from the web as attached.

The shorcoming of this circuit is that the receiver does not have a volume control. I am not certain where should I insert a 10k potential meter for this purpose.

Can I replace R13 with a a 10K potential meter with the wiper connected to the collector of Q4 ?

If not kondly show me where should I insert the volume control in the circuit.

Also please let me know if there is any modification if needed.

Thank you in advance

Best Regards

Low

 

Hello,

I would say no.
It will change the bias of the transistor.
A pot in series with C12 would do the trick.
It will changd the gain of the amplifier stage.

Bertus

 

"B" is right, because the whole circuit prior to that capacitor is actually a low pass filter to keep the quench frequency out of the audio amplifier section. The entire receiver seems to be very much direct coupled as far as DC voltages go. Is this a type-approved commercial product? Or is it a suggestion for an electronic hobby construction project? The reason I ask is because it is a regenerative design, meaning it has an oscillator on the receive frequency, with a potential of interference if it is not operating correctly. This circuit does not appear to have an amplifier stage, which is often used to isolate the antenna from the regenerative detector stage.

 

The audio output of that circuit is line level. It needs to be further amplified by a power amplifier before it can drive a speaker or even headphones. That is where the volume control would be, on the amp, or between the output and the amp.

 

Hello,

I would say no.
It will change the bias of the transistor.
A pot in series with C12 would do the trick.
It will changd the gain of the amplifier stage.

Bertus

Hi,

Thanks for quick response.

May I know the meaning of "A pot in series with C12 would do the trick" ? Do you mean to insert the potentialmeter in series with C12 with the output (terminal 2) connected to the base of transistor Q4, VCC (terminal 1) of the potentialmeter to C12 and terminal 3 to the ground ?

 

"B" is right, because the whole circuit prior to that capacitor is actually a low pass filter to keep the quench frequency out of the audio amplifier section. The entire receiver seems to be very much direct coupled as far as DC voltages go. Is this a type-approved commercial product? Or is it a suggestion for an electronic hobby construction project? The reason I ask is because it is a regenerative design, meaning it has an oscillator on the receive frequency, with a potential of interference if it is not operating correctly. This circuit does not appear to have an amplifier stage, which is often used to isolate the antenna from the regenerative detector stage.

I am doing it as a hobby and for leaning electronic by practical. This circuit is to be try out to see if it works. It is an experiment.

 

Why make it more complicated than necessary?
Put the volume control at OUT, after C16.

 

Hi,

Thanks for quick response.

May I know the meaning of "A pot in series with C12 would do the trick" ? Do you mean to insert the potentialmeter in series with C12 with the output (terminal 2) connected to the base of transistor Q4, VCC (terminal 1) of the potentialmeter to C12 and terminal 3 to the ground ?

"In series " means only TWO connections. So the variable control would add a variable resistance between the connection to C12 and the point that it had been connected to.

 

"In series " means only TWO connections. So the variable control would add a variable resistance between the connection to C12 and the point that it had been connected to.

OK, I got what you mean now. I just got from AI sources that I can add the volume control at two other different points in the circuit ie. between C17 and R17 and between C16 and R16, o you have any comment of this, which is the best option for comfortable listening to the receiver?

 

AI knows zilch about electronics.

The volume control goes after C16.

 

Yes.

Connect Q5 base to the 10k pot wiper.

 

Yes.

Connect Q5 base to the 10k pot wiper.

Not likely to work well... that will change DC bias for the transistor. See #2

 

AI knows zilch about electronics.

The volume control goes after C16.

View attachment 323084

Hi, Is it what you mean?

 

Yes. But the output of the potentiometer cannot drive a loudspeaker. I has to go to a powered speaker such as a PC speaker.

 

Yes. But the output of the potentiometer cannot drive a loudspeaker. I has to go to a powered speaker such as a PC speaker.

Can it drive a small speaker of 8 Ohmn 2 Watt? If not can I amplify this output with an amplifier circuit using LM386 chip?

 

Can it drive a small speaker of 8 Ohmn 2 Watt? If not can I amplify this output with an amplifier circuit using LM386 chip?

 

AI knows zilch about electronics.

The volume control goes after C16.

View attachment 323084

The VERY WORST design I have ever seen on this site came from a request for help to some AI "help" source. That was about a year ago.

 

Yes, you can use the LM386 but some people here don't like the sound quality obtained. You just have to try it for yourself.
Another thing to note, a loudspeaker transducer is just part of the puzzle. The loudspeaker cabinet plays a very important role in the sound output.

On a side note, speakers such as these small portable speakers produce amazingly good output.

 

Yes, you can use the LM386 but some people here don't like the sound quality obtained. You just have to try it for yourself.
Another thing to note, a loudspeaker transducer is just part of the puzzle. The loudspeaker cabinet plays a very important role in the sound output.

On a side note, speakers such as these small portable speakers produce amazingly good output.

View attachment 323106

OK noted. Thanks

 

I am glad that the thread finally came around to the same conclusion I asserted in post #4.