Human 'Antenna' with Regenerative Receiver

[Fischer777]

I have constructed a small one-transistor regenerative receiver, and I have been getting weird results with reception. I have noticed that simply touching parts of the radio, such as the antenna or around where the antenna is attached, will provide great reception. However, when I am not touching the radio it gets rather poor, if any reception. I am mystified by the fact that replacing the antenna with a resistor, inductor, or even a polyethylene capacitor will also provide great reception given that I am holding onto it, and not touching any conductive parts. Reception fails if I touch a ground plane while holding onto the component. I am not sure what phenomena is causing this and why, and I was wondering if anyone might be able to tell me more.

I have provided the electrical diagram of the regenerative receiver (a modified clapp oscillator)

 

[Rooted]

The human body is a conductor, are you simply increasing the size of the antenna?

 

[NascentOxygen]

I have constructed a small one-transistor regenerative receiver,

You're guaranteed hours of fun!

and I have been getting weird results with reception. I have noticed that simply touching parts of the radio, such as the antenna or around where the antenna is attached, will provide great reception. However, when I am not touching the radio it gets rather poor, if any reception.

Any large conductive body (e.g., you) is capacitively coupled to Earth. So wherever you touch the radio you are earthing that point. A small radio receiver such as you have here needs a good earth, together with an antenna, to perform reliably and well. If you are in a strong reception area the antenna may not need to be large, a metal window frame may suffice.

Radio signals move from the antenna to earth, so the better each is, the stronger the signal driving your receiver. It is not really worried if you swap their connections, it's the strength that is important.

You are able to increase the regeneration until it whistles?

 

[Fischer777]

Okay, thanks, that makes a lot of sense now that I think about it. I'll try earthing it and see if that helps. I can increase the regeneration until is whistles/screeches.

 

[alphysicist]

Thank you for sharing your findings with us. It is interesting to hear about your observations with the regenerative receiver and the effects of human touch on its reception. I would approach this phenomenon from an electromagnetic standpoint.

Firstly, it is important to note that the human body is a conductor of electricity, and our skin has a high moisture content which makes it a good conductor. When you touch the antenna or other parts of the radio, you are essentially acting as an extension of the antenna, increasing its length and thus its ability to pick up signals. This is known as capacitive coupling and it is a common phenomenon in radio frequency circuits.

Furthermore, when you replace the antenna with other components such as a resistor or inductor, you are essentially changing the impedance of the circuit, which can also affect the reception. The fact that touching the components while not touching any conductive parts still provides good reception suggests that your body is acting as a ground plane, providing a path for the received signal to travel through.

On the other hand, when you touch a ground plane while holding onto the component, you are essentially creating a short circuit, which can disrupt the flow of the received signal and result in poor reception.

Overall, it seems that your body is acting as an "antenna" or conductor in this circuit, and its effects on reception are a result of capacitive and resistive coupling. I would suggest further experimentation and analysis to better understand the exact mechanisms at play here. Thank you for sharing your findings and I hope this information helps in your research.