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Short wave radio on breadboard

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parthne555

Aug 26, 2020
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Hello,
I have build a SW radio on bread board. I am using LM741 operational amplifier. But after powering it up it does not work. Please see the attached image of the circuit.20200826_091716 (1).jpg
 

Harald Kapp

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This is by no means a short wave radio.
This circuit has so many flaws:
  1. negative supply of the LM741 is blocked by a 47 pF capacitor. SO there is no power to the opamp.
  2. The LM741 requires a minimum supply voltage of +- 10 V, see the datasheet. Operating it from a single 9 V cell is out of spec at the least.
  3. The "-" input of the LM741 is left floating. Even with a correct power supply the opamp will either go into saturation of oscillate wildly.
  4. I see no demodulator circuit. Do you use the input of the LM741 for demodulation?


Where did you get this "circuit" from? It is imho completely useless.
 

parthne555

Aug 26, 2020
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Its UA741 Harald Kapp please see data sheet before saying "useless" to my project
 

Harald Kapp

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Its UA741
How am I to know? you stated LM741 yourself.
please see data sheet before saying "useless" to my project
Please give correct information in the first place.

Apart from the supply voltage which is +- 5 V for the UA741 (still a tad above the 9 V you are trying to work with) my other comments are still valid.
 

parthne555

Aug 26, 2020
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So I removed the 47 pf capacitor. You were right! It was blocking the negative supply. Sorry Mr. Herald Kapp for providing you incorrect information. I got confused as I have both of them.
I got this circuit from this YouTube video


Please watch it. This guy gets confused in pin 6 and pin 7 of 741 opamp please ignore that and watch the rest of the video.
 

parthne555

Aug 26, 2020
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This radio is nothing but a tank circuit resonating a particular frequency gives input to a differentiator(High pass filter). A simple SW radio(based on the frequency band it works best with).
 

bertus

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Hello,

The UA741 also shows +/- 5 volts or 10 volts as minimum power supply.

Bertus
 

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  • UA741CD_to_UA741N_philips.pdf
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davenn

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Its UA741 Harald Kapp please see data sheet before saying "useless" to my project

UA741 is just a variation on a LM741 op-amp from a different manufacturer

It's still just an Op-amp
 

Audioguru

Sep 24, 2016
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The video is missing a schematic and parts list.
The antique 741 opamp was designed 52 years ago. It should be buried. Use a modern amplifier.
The opamp has positive feedback instead of negative feedback.
The radio is missing a Power Amplifier to drive a speaker.
 
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