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Would there be a way to safely use the earth pin from a power outlet as the earth connection for a crystal radio?

kene02
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  • yes. how would you unsafely use the earth? – Kartman Dec 18 '21 at 06:58
  • That's what I was told: don't use the earth pin from a power outlet as your earth because it's dangerous. I mean, wouldn't there be a risk of you getting a electric shock if like a live wire somewhere gets shorted to earth? – kene02 Dec 18 '21 at 07:54
  • You live in Australia, right? – Bruce Abbott Dec 18 '21 at 08:18
  • @Bruce Abbott Correct – kene02 Dec 18 '21 at 08:23
  • You would need two faults, something shorting live to earth, and your house earth bonding becoming detached, for the earth pin to become live. It's not impossible, just rarer than either fault by itself. Perhaps now is the time to check your house earth bonding, which will depend on the electrical codes in your area. It may go to a spike in the ground, it may go to the sheath of your incoming electrical service, it may be bonded to every metallic water/gas service coming onto your property, and maybe the neutral conductor as well. – Neil_UK Dec 18 '21 at 10:12
  • If it’s dangerous, then that means my PC, toaster, oven etc would be dangerous. Whilst the earth becoming live is possible, the general idea is that the earth circuit has a low resistance so it becoming dangerous is highly unlikely. Just about every house in Aust has a MEN that bonds neutral to earth and a grounding rod. Earth leakage breakers are mandated for any new installation or modification. – Kartman Dec 18 '21 at 12:13

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Would there be a way to safely use the earth pin from a power outlet as the earth connection for a crystal radio?

$$\color{red}{\boxed{\text{My answer addresses safety by employing a 1nF to connect to earth}}}$$

To understand why, you should understand what a typical circuit of a crystal radio might be: -

A crystal radio that uses a monopole antenna needs a connection to earth but, it can be quite tenuous and somewhat capacitive. Consider this: a properly designed antenna circuit for a crystal radio might only have circa 10 pF to maybe 100 pF between tuning coil and the monopole: -

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That would give pretty good tuning at 1 MHz: -

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So, on that basis, you could be quite reasonably connect the crystal set earth to "proper" earth via a 1 nF capacitor. If you want to be "safe" make sue it's a capacitor type that is regarded as safe for this type of application. A Y-type capacitor is recommended because they don't fail short circuit. Read this article if you are interested.

And given that a 1 nF Y capacitor wouldn't produce a 50 Hz AC current from 230 volts of more than 100 μA you could connect to live, neutral or earth without risk. All three are bundled together as they pass through the house wiring so all three are quite closely capacitively coupled to earth and, are therefore usable.

$$\color{red}{\boxed{\text{However, I do recommend that you stay clear of live and neutral}}}$$

Andy aka
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