How to Detect Audio vs. White Noise in RF Circuits?

In summary, the person is trying to make an LED light up when audio is detected while using Super-Regenerative receivers. They have researched and found a circuit using a comparator and op-amp. Another suggestion is to use a low pass filter and high pass filter to detect audio vs. white noise and use a comparator to compare the outputs. It is also suggested to attenuate the low pass filter and use the DC current draw to mute the audio amplifier when no signal is received.
  • #1
ddcd
1
0
I have a question about making an LED light up when sensing audio. Right now, I'm using Super-Regenerative receivers and testing various components of them. Using a signal generator, my audio speaker squeals, as it should, when on the right frequency. When it's not on the right frequency, I hear oscillations (white noise). I did a little research and found one circuit with a comparator and an op-amp.

Basically, does anyone have any ideas on how to detect audio vs. white noise? As in, the signal gets quiet during white noise and is loud when on the right frequency.

It's just highly annoying to myself and my classmates having it squeal all the time.
 
Engineering news on Phys.org
  • #2
You could use a low pass filter and a high pass filter with the crossover frequency above the upper end of your audio. When you have significantly more output out of the low pass filter than the high pass, you know you have audio.

The outputs of the two filters could be rectified and compared in a comparator. I would attenuate the low pass filter so that the comparator won't indicate audio unless it is clearly present. Connect the LED to the output of the comparator so that when audio is present, it lights up.
 
  • #3
I made some super-regen circuits a long time ago. They are notoriously noisy when they are not receiving a signal, but give amazing sensitivity for simple circuits.

On thing I noticed on mine was that the DC current drawn reduced a lot when it was receiving a signal.

It would be worth finding out if yours is the same. It may be possible to use this effect to mute the audio amplifier when there is no signal being received.
 

Related to How to Detect Audio vs. White Noise in RF Circuits?

1. What is an LED comparator for RF circuits?

An LED comparator is a device used to compare the voltage level of an RF signal with a reference voltage. It is used to detect changes in the RF signal and trigger an LED to turn on or off, indicating the presence or absence of the signal.

2. How does an LED comparator work?

An LED comparator works by comparing the voltage level of the RF signal with a reference voltage. When the RF signal surpasses the reference voltage, the comparator triggers the LED to turn on, and when the signal falls below the reference voltage, the LED turns off.

3. What are the advantages of using an LED comparator for RF circuits?

Using an LED comparator allows for quick and easy detection of changes in RF signals, making it useful in applications such as signal strength monitoring and frequency detection. It also has a simple design and is cost-effective compared to other methods of RF signal detection.

4. How accurate is an LED comparator for RF circuits?

The accuracy of an LED comparator depends on the precision of the reference voltage and the sensitivity of the LED. With proper calibration, an LED comparator can provide reliable and accurate results for detecting RF signals.

5. Can an LED comparator be used for other types of signals besides RF?

While an LED comparator is primarily used for RF signals, it can also be used for other types of signals, such as audio or video signals. It can be calibrated to detect different voltage levels, making it a versatile tool for various signal detection applications.

Similar threads

  • Electrical Engineering
Replies
28
Views
4K
  • Electrical Engineering
Replies
3
Views
978
  • Electrical Engineering
Replies
12
Views
3K
  • Classical Physics
Replies
25
Views
2K
  • Electrical Engineering
Replies
9
Views
1K
  • Electrical Engineering
Replies
15
Views
11K
Replies
9
Views
2K
  • Electrical Engineering
Replies
2
Views
3K
  • Electrical Engineering
Replies
30
Views
3K
Replies
29
Views
4K
Back
Top