Why my radio cannot receive any radio station?

Ask questions about projects relating to: aerodynamics or hydrodynamics, astronomy, chemistry, electricity, electronics, physics, or engineering

Moderators: kgudger, bfinio, MadelineB, Moderators

Locked
nabati
Posts: 1
Joined: Mon Feb 13, 2017 2:28 am
Occupation: Student

Why my radio cannot receive any radio station?

Post by nabati »

Hi,everyone. Actually I'm a college student now. I'm so interested in electronic,and I always did some design and research.

Recently I've made two different circuits to receive RF using LM386 but they doesn't work. I've changed the values of C2 and L1 to change the frequency. I've also changed the gain but nothing happens.

The problem is that I hear a sound of noise or buzz from the speaker. When I touch Pin 3 (The input) or the Antenna, The sound become higher but anyway no radio station is received.

Image

I've made a radio transmitter using a transistor before so, I turned it on. The receiver circuit received the song Which is the input of the transmitter. It receives no matter the values of the C2 and L1 of the Tank circuit so, I removed the tank circuit and connected the antenna directly to pin 3 and It also works receive the song.

Why it doesn't receive any radio station although it receive the signals that are transmitted by the transmitter circuit that I've made ?

What can I do to receive radio stations ? ( I live in area Where I can receive good radio stations AM and FM from my cell phone and Radio device )

here is the details of the IC : http://www.kynix.com/Detail/274538/LM386.html
PharmaMan
Expert
Posts: 153
Joined: Sun Jul 19, 2015 7:45 pm
Occupation: Biomedical Sciences Graduate
Project Question: Registration as an Expert
Project Due Date: N/A
Project Status: Not applicable

Re: Why my radio cannot receive any radio station?

Post by PharmaMan »

Hello and thank you for your post.

I would try posting this in the Physical Sciences forums. This is the Life/Earth Sciences forum. They will be able to help you out more over there.

Best,
Pharma
rmarz
Expert
Posts: 634
Joined: Sat Oct 25, 2008 1:26 pm
Occupation: Technology Consultant
Project Question: n/a
Project Due Date: n/a
Project Status: Not applicable

Re: Why my radio cannot receive any radio station?

Post by rmarz »

nabati - An interesting thing about this schematic is that the Coil/Capacitor tank circuit appears to be wired to act as a 'bandpass' filter, then the diode is supposed to demodulate the AM signal. The LM386 is just providing audio amplification. It is, in essence, a crystal set with amplification. It's possible that the choice of L/C values is far off any resonant frequency for the AM band, approximately 0.5 to 1.6 MHz. In most crystal set schematics, the diode is usually placed at the connection of the antenna and coil, or at some tap along the coil. If you try this location, you might also try to connect the lower end of the tank circuit to ground. If you know the L/C values, plug them into a formula to determine the real resonant frequency. Change the values if possible to get into the 1.0 MHz range.

I don't know why your AM transmitter received the signal and you can't receive a commercial station. Possibly the short distance from your transmitter to receiver provided a much stronger signal strength.

Rick Marz
rmarz
Expert
Posts: 634
Joined: Sat Oct 25, 2008 1:26 pm
Occupation: Technology Consultant
Project Question: n/a
Project Due Date: n/a
Project Status: Not applicable

Re: Why my radio cannot receive any radio station?

Post by rmarz »

nabati - Found this schematic that might offer some assistance.

Rick Marz
crystal set 386 amp.pdf
(10.99 KiB) Downloaded 242 times
Locked

Return to “Grades 9-12: Physical Science”