Electronics > Beginners

Crystal Radio Breadboard - Zero Sound

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t1d:
Thanks guys!

glarsson:
RF circuit built on a breadboard? Lots of extra C in the breadboard and extra L in the flying leads.

metrologist:
I am trying to remember if I hear static noise on this simple crystal radio. I suspect normally not and the tuning is very sensitive, so it's easy to miss a station.

As said, you have to unwind the antenna and get it up in the air. The antenna is the only source of power so you will need a large aperture to capture enough energy to produce enough current in the circuit to get any sound.

Later I'll post some inductors that I built. I like open air wound inductors and in a basket weave. What kind of inductor are you using? BTW, an awesome way to integrate the inductor and antenna is to make the inductor the antenna in the form of a very large coil. I've seen some that are larger than a full grown man. I think mine is about 2 feet diameter and something like 16 turn primary and 3 to 5 turn secondary.

Below are some classic simple designs.

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

t1d:

--- Quote from: metrologist on December 19, 2018, 06:29:34 pm ---As said, you have to unwind the antenna and get it up in the air. The antenna is the only source of power so you will need a large aperture to capture enough energy to produce enough current in the circuit to get any sound.
--- End quote ---
Yep, will do.

--- Quote from: metrologist on December 19, 2018, 06:29:34 pm ---Later I'll post some inductors that I built. I like open air wound inductors and in a basket weave. What kind of inductor are you using?
--- End quote ---
Just the little ones that look like common TH resistors. One of my ultimate design goals is to make a micro design, for minimalist camping.

--- Quote from: metrologist on December 19, 2018, 06:29:34 pm --- BTW, an awesome way to integrate the inductor and antenna is to make the inductor the antenna in the form of a very large coil. I've seen some that are larger than a full grown man. I think mine is about 2 feet diameter and something like 16 turn primary and 3 to 5 turn secondary.
--- End quote ---
Cool...

--- Quote from: metrologist on December 19, 2018, 06:29:34 pm ---Below are some classic simple designs.
http://www.techlib.com/electronics/crystal.html

--- End quote ---
Thanks!

t1d:

--- Quote from: alanb on December 19, 2018, 05:16:11 pm ---You can calculate the frequency with this
http://www.calctool.org/CALC/eng/electronics/RLC_circuit

--- End quote ---
I looked at the link and I wasn't sure how to enter the information... What I would like to do is specify that:
- The channel is 710KHz, as it is AM.
- The resistance is 82K Ohms.
- The capacitance is midpoint of 0-335pF variable cap = 1/2 x 335pF = 167.5. Thereby, I can tune it, up or down.
Calculate the needed inductance, for the inductor.

I fooled around with the numbers and I may have hit it just about right... Using 82K Ohms, 167.5pF and just subbing in 300uH, the resonant frequency is 709.99KHz... That's nigh on perfect... Did I end up with the correct inductor value, or am I reading things incorrectly?

Thank you.

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