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Old 20th Aug 2019, 7:14 am   #1
vu2nan-nandu
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Default Tarnished Silver as a Crystal Radio Detector

A fully tarnished, shiny black silver artefact was tried out as a detector in place of the germanium transistor in my series-tuned, shunt-fed crystal radio.

https://3.bp.blogspot.com/-1-l4oSSvN.../untitled1.JPG

Fortunately the presence of an untarnished spot facilitated the metal to metal connection.

A length of pencil 'lead' was used to probe the tarnished portion to locate the 'sweet spot'.

Excellent reception of the local 612 kHz, 200 kW AM broadcast station was obtained using a 60'
wire antenna and sound-powered phones. Headphone current, measured using a 1mA FSD 60 Ω meter, was 300 μA as compared to 750 μA with the germanium transistor and 50 μA with a razor blade as the detector.

It was a confirmation of the shiny black tarnish being silver sulphide (a semiconductor).

A silver coin, stored in a plastic pouch and tarnished a dull grey, in its failure to detect, indicated that its tarnish was silver oxide (a good conductor of electricity).

Regards,

Nandu.
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Old 21st Aug 2019, 10:20 pm   #2
rambo1152
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Default Re: Tarnished Silver as a Crystal Radio Detector

A used Gillette razor blade was all I could afford to go with my pencil.

Does tarnished EPNS work just as well, or does it have to be solid silver?
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Old 22nd Aug 2019, 6:44 am   #3
vu2nan-nandu
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Default Re: Tarnished Silver as a Crystal Radio Detector

Hi OM Graham,

The razor blade I used was a 'Gillette Platinum' (not blue).

The small embossed resin-filled artefact is made of silver foil and had been lying in the loft for years.

I suppose a well tarnished EPNS piece would work just as well.

Have fun!

73,

Nandu.
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Old 22nd Aug 2019, 10:08 pm   #4
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Default Re: Tarnished Silver as a Crystal Radio Detector

It's surprising how many materials will work in this application. I tried quite a few various metallic household items in a crystal set a few years back. Even a piece of coal/coke will work if I remember correctly. Be careful though, it can develop into an obsession!
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Old 23rd Aug 2019, 5:04 am   #5
TonyDuell
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Default Re: Tarnished Silver as a Crystal Radio Detector

I believe a lump of coke is suggested in the 'Experimental POW radio' page in the Ladybird book 'Making a Transistor Radio'. That is the one page of the book I never tried as a kid.

I was talking to a teenage-ish audience about crystal detectors and mentioned that a 'lump of coke' can work. Seeing puzzled looks around the room I added 'The fuel. Not the soft drink.... or the drug'
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Old 23rd Aug 2019, 5:57 pm   #6
Herald1360
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Default Re: Tarnished Silver as a Crystal Radio Detector

Hmmm, anybody tried it? Might be a whole new type of signal sniffer.....
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Old 23rd Aug 2019, 6:13 pm   #7
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Default Re: Tarnished Silver as a Crystal Radio Detector

I suppose that the main requirement of the detector material is that it can be made non-linear in some way. Hence many combinations of metals and general junk with corrosion/tarnish may work to a degree. As I have mentioned before on the forum when discussing crystal sets, I live not far from a long defunct lead and mineral mining area, and with a bit of patience and good eyesight you could still find galena crystals on the overgrown spoil heaps.
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Old 4th Sep 2019, 5:45 pm   #8
Pete_kaye
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Default Re: Tarnished Silver as a Crystal Radio Detector

A few years ago , I used a small piece of coke I picked from afireplace. the whisker was coiled piece of top E guitar string. It was nearly as good as Galena and quite stable once set up.
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Old 6th Sep 2019, 1:17 pm   #9
dominicbeesley
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Default Re: Tarnished Silver as a Crystal Radio Detector

I'm following this with interest. I was at the Lead Mining Museum in Dumfrieshire recently and picked up a load of likely looking specimens from some spoil heaps. I'm looking forward to getting my workshop back and trying them out!
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