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 Post subject: Tarnished Silver as a Crystal Radio Detector
PostPosted: Aug Thu 22, 2019 6:50 am 
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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.

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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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Last edited by vu2nan on Sep Fri 13, 2019 5:09 am, edited 1 time in total.

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Aug Thu 22, 2019 1:09 pm 
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Location: Norfolk, VA
Silver sulfide for the win!........

https://en.wikipedia.org/wiki/Silver_sulfide

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Aug Fri 23, 2019 3:17 am 
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Thanks, Brian!

Regards,

Nandu.

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Aug Sat 31, 2019 6:46 am 
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Joined: Mar Sun 14, 2010 2:51 am
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Location: Newport, Oregon, 97365 U.S.A.
There is a book published in the U.S. this year, 2019, "Foxhole Radio" by Brian Carusella. Believe me, this is the last word on the
Foxhole Radios topic ! In the back there is a comparison of various razor blade detectors compared to a germanium fixed diode.
It is sort of amazing that with the low effectiveness of the razor blade, the soldiers were able to hear anything !


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Sep Sun 01, 2019 2:50 am 
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Hi Hue,

The real high power of the broadcast stations of that era may have been one of the factors that gave birth to the foxhole radio.

Regards,

Nandu.

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Sep Sun 15, 2019 4:52 pm 
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Listening to music with a filling in my right rear molar.

Norm

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Sep Sun 22, 2019 3:26 am 
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Norm Johnson wrote:
Listening to music with a filling in my right rear molar.

Norm

:D
Regards,

Nandu.

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Feb Fri 07, 2020 1:52 pm 
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Joined: Feb Mon 21, 2011 3:35 pm
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Hue, thanks for the good words about my book! I hope you enjoyed it as much as I enjoyed researching it.
Brian


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Mar Sun 01, 2020 6:33 pm 
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Joined: Jan Thu 09, 2020 6:46 am
Posts: 71
Location: Lexington, KY, USA
I actually built a crystal radio when I was a kid with a chunk of galena that I personally pulled out of an abandoned lead mine in Galena, Illinois. I suspect that they don’t do field trips for kids to LEAD mines any more...


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Mar Wed 18, 2020 11:30 am 
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Somewhat ot but I was surprised when I tried out a detector without any tuning arrangements, just a diode and bit of wire for aerial, and yes, I could clearly hear my local station with another in the background - so going to all the trouble of coils and tuning in foxhole sets wasn't really necessary. Some people probably could hear radio through their teeth.


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Jun Mon 01, 2020 2:32 am 
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Joined: Jul Thu 12, 2007 9:36 am
Posts: 484
Location: Boston,Ma
Hey OM Nandu,

Good to see you in here.Been a long time. I've seen your posts over the years since we last talked and always enjoy your ideas.

I am still messing around with crystal radio although for now antenna options are limited.

My best Foxhole was built using only a "hammer" rock, a candle and a knife. "Coil dope" is chewed up Wrigley's Spearmint gum- now rock hard- which could have come from C Ration packs . Has taps and blue blade/ safety pin. SUPER touchy, but did work. Using a pencil was "easier" , but still touchy .

Also done lots of other dissimilar detector stuff in the past. It seems these types of sets like BIG signals to "goose" them into working.

My advice for beginners is to DEFINITELY use a good diode first to get a strong signal on ANY radio (Foxhole or otherwise), THEN play with blade , silver , copper, iron, etc, as a detector . Applying a bias is also an option.


73's de N1NQC


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Jun Fri 05, 2020 10:42 pm 
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Joined: Mar Sun 14, 2010 2:51 am
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Location: Newport, Oregon, 97365 U.S.A.
Somewhere on the net i saw a fascinating great article on using an imperfect contact on a piece of metal for a negative - resistance, low power transmitter.
It occurred to me that the same negative resistance feature could be used for a regenerative receiver. But because the bias voltage is very critical, i think you want to control oscillation by damping of the tuned circuit.


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Jun Fri 05, 2020 11:37 pm 
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Location: Sanford Fla 32771 (USA)
OldHack wrote:
I actually built a crystal radio when I was a kid with a chunk of galena that I personally pulled out of an abandoned lead mine in Galena, Illinois. I suspect that they don’t do field trips for kids to LEAD mines any more...

I have had this chunk of rock for as long as I can remember. Somebody told me it was galena, no idea. Anyway to verify short of sending it to a rock hound (geologist)?
Woops, cpu crashed. Be back with pic shortly.


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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Jun Wed 17, 2020 10:30 am 
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krystallo wrote:
Hey OM Nandu,

Good to see you in here.Been a long time. I've seen your posts over the years since we last talked and always enjoy your ideas.

I am still messing around with crystal radio although for now antenna options are limited.

My best Foxhole was built using only a "hammer" rock, a candle and a knife. "Coil dope" is chewed up Wrigley's Spearmint gum- now rock hard- which could have come from C Ration packs . Has taps and blue blade/ safety pin. SUPER touchy, but did work. Using a pencil was "easier" , but still touchy .

Also done lots of other dissimilar detector stuff in the past. It seems these types of sets like BIG signals to "goose" them into working.

My advice for beginners is to DEFINITELY use a good diode first to get a strong signal on ANY radio (Foxhole or otherwise), THEN play with blade , silver , copper, iron, etc, as a detector . Applying a bias is also an option.


73's de N1NQC



Hi OM Kevin,

It's nice to get back in touch. Yes, it's been quite a while.

I'm glad you find some of my ideas interesting.

I guess we all start with crystal radio and come full circle to delve deeper.

I'm very sorry for my delayed response. As a grandfather of three I am unable to spare as much time to the hobby as I would like to!

Have fun!

73,

Nandu.

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 Post subject: Re: Tarnished Silver as a Crystal Radio Detector
PostPosted: Jun Wed 17, 2020 9:46 pm 
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Joined: Jan Sat 25, 2020 5:23 am
Posts: 100
Location: Colorado Springs, CO 80917
There's quite a few minerals that resemble galena, especially oxidized galena. And some that will act as a detector more or less. Chip off a bit for a shiny surface & give it a try.


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