Post Number: 1
|Posted on Friday, December 22, 2006 - 10:42 pm: || |
So I've been looking at a few more complicated schematics for basic AM recievers, and I've tried to build a couple, always resulting in failure, so I decided to do something extremely basic, without even a tuner, just hoping to pick up some static, and it has still resulted in failure. I hear the initial feedback when plugging in the headphones, then complete silence. Could anyone fill me in on what I did wrong? By the way I'm really new to this kind of stuff, so thanks for the patience =D
Below is my schematic.
I. Dimov (Overrider)
Post Number: 118
|Posted on Saturday, December 23, 2006 - 5:59 pm: || |
The impedance of the headphones is too low, or the ninevolt battery is jamming the signal, also it could be the diode. It must be germanium.
Post Number: 3
|Posted on Saturday, December 23, 2006 - 6:06 pm: || |
If it is the 9v battery jamming the signal, what can I do to stop that, use less battery power?
And I'm not using a germanium diode, but what makes a rectifier diode not usable for this situation?
Oh, and I also just discovered that my headphones have a 32 ohm impedance. How can I tell if that is too low or high?
Thank you for the help, I'm very new to this
(Message edited by codym on December 23, 2006)
Simon Quellen Field (Sfield)
Post Number: 1605
|Posted on Saturday, December 23, 2006 - 8:57 pm: || |
The battery is doing nothing in this circuit.
Likewise for the rest of the parts, since they are not put
together in any meaningful manner.
Read the entire radio chapter. It is not that long, it will probably
take you less than an hour:
Just throwing parts together and hoping will not do it, you have to have
some basic theory.
32 ohms is too low for a crystal radio, and you have no amplifier, so you
are trying to build a crystal radio, although you have added a battery,
despite having no parts that can use one. You want an impedance between
1,000 to 1,000,000 ohms.
You can convert your headphones to an impedance that will work by using
an audio transformer:
Throw away your circuit, and use the one on this page:
Connect the 1,000 ohm side of the transformer where the piezoelectric
earphone is in that schematic. You won't need the middle leg of the
transformer -- leave it unconnected.
Connect the 8 ohm side of the transformer to your headphones.
You can get all the parts for the radio here:
It is guaranteed to work.
Post Number: 4
|Posted on Sunday, December 24, 2006 - 2:06 am: || |
Thank you very much for the input. The site is an awesome referrence, and has motivated me greatly to do projects like this, and you, Simon, are a very knowledgeable and helpful individual, and I appreciate how willing you are to teach those in need. I also appreciate the people in the forum for being so helpful.
I am looking forward to putting this together, but since it's the holiday season, all the electronic stores in my area are closed for the next few days. As soon as they open back up, I'll get what I need and tell you how it goes!