Electronics > Beginners
Crystal Radio Breadboard - Zero Sound
spec:
Hi t1d
Check
[1] earpiece by connecting it to an audio source
[2} diode, especially back to front ratio (use 1V5 battery, 10k resistor in series and multimeter set to uA range).
The antenna matching will be rather poor with that circuit and the antenna reactances, both capacitive and inductive, will pull the resonant frequency all over the place.
james_s:
I remember building a crystal radio kit when I was a kid. As I recall there was no background noise, I only got anything when I tuned a strong enough signal. It needed a good solid ground and a long wire antenna to work at all.
mikerj:
--- Quote from: chris_leyson on December 20, 2018, 08:45:23 pm ---I remember as a kid sitting for hours reading an old science book on my dads bookshelf, Science for the Citizen by Lancelot Hogben. "Dad, I want to build a crystal radio" so next weekend of we go to L.H.Evans in Cardiff market and buy all of the required parts. A 350pF film tuning cap, a Denco coil, an OA47 and a crystal earpiece. Wow that was fun and it worked reasonably well with a 50' long wire. I didn't have any luck building a single valve super regen but 50 years later I might have another stab at it just for fun. L.H.Evans is still there in Cardiff market and A simple crystal radio was the "spark" that got me into electronics.
--- End quote ---
Pretty much the same here, though I was given a Ladybird book "Making a Transistor Radio" which started with a crystal set and expanded it a regenerative design with speaker output.
I remember the crystal set not working very until I grounded it on a water pipe and local stations were then loud enough to hear clearly without putting the earpiece in your ear.
StillTrying:
--- Quote from: metrologist on December 21, 2018, 12:56:49 am ---
--- Quote from: StillTrying on December 20, 2018, 10:06:32 pm ---With a scope you could ping the tuned circuit to see if it rings at ~700kHz.
--- End quote ---
How do you ping?
--- End quote ---
Flick a 1V5 battery across the coil circuit through a 470R. In a simulation with 300uH, 165pF + 20pF scope, the ringing is ~650kHz which is about right.
As in the very first post, the RC time of 10n + 82k is too long. yellow
The recommended 1n + 82k gives a much better output. blue
Zero999:
--- Quote from: cdev on December 20, 2018, 07:11:54 pm ---Shortwave signals may only be audible at night, but they will fill the bands at higher frequencies than AM (fewer turns required)
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I thought that short wave is mostly single side band, which can't be picked up with a diode detector?
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