Re: 2 Transistor AM Radio

"Dave.H" (the1930s@xxxxxxxxxxxxxx) writes:
On Feb 5, 10:42 pm, "Dave.H" <the19...@xxxxxxxxxxxxxx> wrote:
On Feb 5, 10:34 pm, Chris <cfoley1...@xxxxxxxxx> wrote:



On Feb 5, 4:11 am, "Dave.H" <the19...@xxxxxxxxxxxxxx> wrote:

Not sure if this is the correct place to ask, but here goes... I've
found plans for a simple two transistor AM radio receiver, but I'm not
sure how the ferrite loop antenna is connected to the radio. I'm not
at all good with schematics, I can understand most of it except for
the ferrite antenna bit. I would appreciate any help on this.

http://www.techlib.com/electronics/crystal.html#Simple2transistor

Hi, Dave. If you look at the picture, you can see 4 turns of yellow
insulated wire around the loopstick. As shown in the schematic, one
wire is connected to the base of the first transistor, and the other
is connected to the + end of the 47uF cap and the 270K ohm resistor.
You've also got two very thin magnet wires (one red, one blue in the
illustration) which go to the tuning capacitor.

The idea is, you make the 4 turns with your own wire around the
existing loopstick, which you've scrounged from a garage sale
transistor radio along with the tuning cap. Be careful not to break
the wires coming from the loopstick -- use a tweezers and a lot of
care when you pull it.

Hope this has answered your question. The radio shown is fairly
simple, and shouldn't be too difficult to build. If you're going with
trying to build on a real piece of wood board, use pine instead of oak
(softer, easier to work and pound nails), and use brass nails (most
nails don't accept solder). If you can find someone with a little
electronics experience to help a bit it should be easy.

Good luck
Chris

I'm building it in a plastic project box, for portability reasons.
Should a 60-160 pF tuning cap work in this radio? I'm also wondering
how to hook up a 1 kohm - 8 ohm audio transformer so I can use my iPod
earphones with it. The transformer has three wires on one side, and
two on the other from what I can see in the picture.

The ferrite rod antenna I'm planning to use has four wires, how would
I hook this up the the tuning cap?

Chances are pretty good it alreayd has the needed pickup loop.

Likely one winding is quite large, and will resonate with the variable
capacitor. And then a small winding of a small number of turns to couple
the signal out of that resonant circuit.

Michael

.

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