I need help troubleshooting my DIY radio. I am following the schematic this link.

See pictures below for a diagram of how the components are wired and the actual wiring. The design I made is different from the schematic because I am restricted to a 3.5mm aux port.

  • Transistor = 2N2222A
  • Variable capacitor = 12 - 60 pF
  • Audio is connected to a 3.5mm aux port

The values I've collected through the circuit are the following

  • Ic = 90 mA
  • Ib = 0.5 mA

I've switched out every component and I still do not get any sound. Hand drawn schematic of a DIY AM radio

  • 3
    \$\begingroup\$ If Ib = 4.3mA you aren't following the circuit, which has a 100 kilohm bias resistor. And an 8 ohm speaker is a LOOONG way from the high impedance earphone. \$\endgroup\$ Feb 2 at 21:43
  • \$\begingroup\$ what kind of sound are you expecting? ... is there an AM radio transmitter in your area? \$\endgroup\$
    – jsotola
    Feb 2 at 21:43
  • 4
    \$\begingroup\$ The article specifies a 64 ohm headphone, not an 8 ohm speaker. A simple circuit like this produces very little power, a headphone is necessary. \$\endgroup\$
    – Mattman944
    Feb 2 at 21:44
  • \$\begingroup\$ 100% you need a proper earphone. THis can not drive a speaker \$\endgroup\$
    – Kyle B
    Feb 2 at 21:47
  • 1
    \$\begingroup\$ Draw a schematic with your circuit components and copy origional circuit. It is too confusing to go back and forth. Come in Moscow.... \$\endgroup\$ Feb 2 at 21:50
  1. The page you link to leaves out some of the most critical details - how many windings are on the coil, made from what wire, and how big (diameter) is the coil form. With out that, you can't build it and expect it to do anything
  2. You have ignored the parts that are described, and substituted other parts with no thought to how it all works together.

The description you picked to follow is incomplete, and you ignored what directions it does have.

You should find a project with all the needed details, use the listed parts, and assemble it according to directions.

This PDF explains how AM radios work and describes how to build them. Follow the instructions. Many people have built simple AM receivers. It isn't difficult, but you can't just replace parts or use random junk.

  • \$\begingroup\$ Great book recommendation! Should be required reading before asking a question about why a DIY AM radio isn’t working. \$\endgroup\$ Feb 2 at 23:18
  • \$\begingroup\$ Thanks for the pdf, i'll look into it. \$\endgroup\$
    – Adrian
    Feb 5 at 2:26

Your antenna is probably not resonant to MF broadcasts, which are in the hundreds of kilohertz range. For AM receive antennas, a small receive loop (which you can find cheap on Amazon) or a ferrite rod wrapped with enamal-coated wire (speaker wire will do). I suggest you use a proper AM antenna instead of building your own, as the latter may have issues receiving unless you are quite close to a broadcast station.

If you are close to a broadcast station, there's a cooler project I suggest you attempt instead: building a crystal radio. Those don't require a battery, instead harvesting energy from the airwaves to power itself. In the circuit you provided, the transistor serves the purpose of amplifying the received signal using your battery power, but makes things a bit more complex.

If you decide to get a receive loop, it will probably have a small plug connector. You can hook up the tip to the coupling capacitor, and the other end to ground.

  • \$\begingroup\$ Ahem "MF" broadcasts? There's no need for profanity. \$\endgroup\$
    – K H
    Feb 3 at 0:47
  • \$\begingroup\$ Profane only in that it medium frequency is not sacred. en.wikipedia.org/wiki/Medium_frequency \$\endgroup\$
    – Jasen
    Feb 3 at 2:01
  • \$\begingroup\$ I took the antenna from an old radio. I remember seeing an inductor between the antenna and the circuit. I'll add the inductor and see if it makes a diff. \$\endgroup\$
    – Adrian
    Feb 5 at 2:25
  • \$\begingroup\$ @Adrian: You need to figure out why the inductor was there. It will have some function and interact with other components. You can't just chuck stuff together. You need to learn how do design - especially when you have a restricted collection of parts. It means doing some calculations and measurements. \$\endgroup\$
    – Transistor
    Feb 6 at 20:47

You list 7 components in your post #1. 5 of them are incorrect, and any 1 or those 5 will cause the circuit not to work.

Change the incorrect components and try again. After that, please draw your exact schematic as wired, with component values and reference designators, and post it.

  • \$\begingroup\$ I am as close as I could to using the components listed in the schematic with what I have. \$\endgroup\$
    – Adrian
    Feb 5 at 2:23

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