... crystal radios work without battery or mains. (And I'm not talking of crank/wind up radios).
I haven't used a crystal radio for probably 35 years and I am not sure what you'd pick up nowadays (probably only Radio Moscow or your local Asian station on MW) but they are dirt cheap to make and, despite the name, they don't need a crystal.
Well they do need a germanium diode.
Which is what the original 'cats whisker' and crystal , was.
>
Sadly, not much use unless someone is transmitting something that you can tune in to. Might just as well buy an old south-sea sea shell and listen to the sound of 'waves'.
The one I built as a kid used the latter. Couldn't hear much on it though.
Wasn't that galena (lead sulfide)?
I've got a Truvox radio jack here. Basically a crystal set you plugged into a tape recorder, etc many moons ago. My school used them to record schools broadcasts in the 50s.
Still works. On LW and MW. With a decent aerial.
....and earth
My set, the problem with it was that it had no selectivity. The stations were just a jumble.
But it did have a lot of signal. You could leave the piezo headphones on the table, and get room filling sound.
The detector was a 1N34A. That was practically the first new electronic part I ever bought.
Mine picked up AM between 550KHz and 1200KHz or so. I don't think any other bands were coming in. They would be swamped at that time, by the level of AM transmission used.
If there was an emergency broadcast of some sort, my little set would never have made it intelligible.
And when I got one of those Ferranti three-legged things, I don't think that was intelligible either. Still the same problem that Paul could not make a tuned circuit worth a darn :-)
Paul
I think it probably was,
Usually, although other things were used - perhaps the most famous being a razor blade.
Germanium diodes came along later, when crystal sets were little more than things budding radio amateurs / geeks played with.
You should still be able to receive stations on MW and LW with one. I last demonstrated one perhaps 20 years back and was able to receive several stations. You need a long bit of wire for an antenna - ideally 50 + ft and and earth, another length of wire along the ground about the same length would do.
I used to have a beautiful Bakelite Crystal set but it went astray over the years. It may be in one of the boxes in the loft.
Any AM station close enough.
But do need a diode.
Easily fixed with a better design.
Bullshit on the room filling.
But a better designed one would.
Good luck with receiving DAB!
I could only ever get Radio 4.
Home Service
Bill
Even with a DAB receiver you would struggle without mains power. In a power cut they eat batteries at a rate of four per 8 hours of use.
A classic analogue FM radio would last more than a week!
Is that a more likely station? We (a gang of lads that were interested in odd things) used to make crystal sets with things like denuded sprung mattresses, or even old motorbikes, as aerials, and only ever got the one station. I think we guessed it was Radio 4, but it was too long ago to be certain. I still have the Ladybird book that we more or less followed, and a couple of the old OC71's.
The zn 414, was not intended as a straight crystal set but just a detector of am on a radio, that had more gain than just a diode, often meaning you could get away with only on IF stage. It needed to be lightly coupled to the tuned circuit to maintain the Q in the circuit. Often transfilters tended to get used and these though selective were low output. As for Crystal sets, well, a one transistor free power circuit using a germanium transistor like an oc44 actually worked quite loudly with a crystal earpiece, but you were still playing with a very low impedance input and it needed to be lightly coupled to get selectivity. Used to work quite well on long wave with a good aerial. I am told that some mosfets can be used as well as their gate is higher impedance, but I'd seriously doubt it would work well being made of silicon. Brian
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