Can I replace R13 with 10K Potentialmeter as the volume control in the circuit?

Thread Starter

lsk2141

Joined May 24, 2024
9
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
 

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bertus

Joined Apr 5, 2008
22,304
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
 

MisterBill2

Joined Jan 23, 2018
19,398
"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.
 

BobTPH

Joined Jun 5, 2013
9,264
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.
 

Thread Starter

lsk2141

Joined May 24, 2024
9
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 ?
 

Attachments

Thread Starter

lsk2141

Joined May 24, 2024
9
"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.
 

MisterBill2

Joined Jan 23, 2018
19,398
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.
 

Thread Starter

lsk2141

Joined May 24, 2024
9
"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?
 

MrChips

Joined Oct 2, 2009
31,076
Yes. But the output of the potentiometer cannot drive a loudspeaker. I has to go to a powered speaker such as a PC speaker.
 

Thread Starter

lsk2141

Joined May 24, 2024
9
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?
 

MrChips

Joined Oct 2, 2009
31,076
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.

1716585338185.png
 

Thread Starter

lsk2141

Joined May 24, 2024
9
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
 
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