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Crystal Radio without an antenna

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wolf9545

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I am a geocacher, username = wolf9545, and I just received the Geico travelbug. What I am looking to build to attach to it is a crystal radio. All of the circuits that I found for crystal radios have you connect it to a long wire for the antenna or to a cold water pipe for a ground. Is there any crystal radio circuits that don't need a long antenna? This way it would just be a little box, without batteries, that would be moved around.
 

Reloadron

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Most Helpful Member
The long wire antenna for radios like that are the nature of the beast. I built my share as a kid, believe me. The long wire and good ground are why it works in the basic simple versions. No tuning, just a crystal (like the old 1N34 Germanium diode) headphones and wire.

Ron
 

transistor495

Member
Forum Supporter
Not possible without a longer wire and it definetely isn't intended for portable units.

A crystal radio sucks its required energy from radio waves and it works best with a strong radio station nearby with a longer wire antenna pulls in energy and of course, the cold water ground pipe adds the potential boost, and if and only if you can grab a high impedance headphone units or crystal earpiece :)
 

wolf9545

New Member
It would have been neat to have the travelbug travel from cache to cache and have people post what radio station was picked up. I didn't know if there was a way to have the antenna be wound around a can / jar to make it a little more portable?
 

carbonzit

Active Member
I guess it all depends on how far you can stretch your definition of "crystal radio" ...

One could make a small, primitive radio that fit in a small container, but lacking a long antenna and ground connection, you'd need to incorporate at least one stage of RF amplification. Now, where I come from, that would get you kicked right out of the Crystal Radio Club. Don't know what the rules are where you are.

The point is, it might be possible to make a small, self-contained, primitive DIY radio that will meet your purposes. But the classic powered-by-the-air crystal radio design is not gonna work here.
 
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Sceadwian

Banned
As said already it won't be a 'crystal radio' but use the ferrite loop core that just about all AM receivers in existence use, they're only about 1 inch long and 1/3-1/2 an inch in diameter, and with amplification will pick up a LOT of stations.
 

carbonzit

Active Member
Yes. Amplification plus tuning. You need a fairly high-Q resonant circuit to bring in relatively weak stations.
 

crutschow

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Most Helpful Member
I've heard of attempts to make crystal radios that use one crystal to rectify the signal from a close strong station (still using a long antenna of course) and use that to power a simple amplifier stage so you can pick up stations further away.
 

carbonzit

Active Member
You say "attempts", so I get the feeling that they may have been none too successful.

I think if I was going to go that route, I might just try a potato or lemon-juice battery instead ...
 

Sceadwian

Banned
crut, you'd have to be REALLY close to get any kind of real power out of it. Just put a battery in it =\
 

Reloadron

Well-Known Member
Most Helpful Member
I've heard of attempts to make crystal radios that use one crystal to rectify the signal from a close strong station (still using a long antenna of course) and use that to power a simple amplifier stage so you can pick up stations further away.
When I was a kid I used a 1N34 Germanium diode as the detector (I actually also had a cat whisker) and using a long wire antenna (my 1/2 wave 40 meter dipole) I could get WHLI on Long Island (1100 on your AM dial). I think back then they were running about 5 KW, nothing like the big clear channel stations of the day. Their transmitter antenna was located about maybe 4 to 5 miles from me. Reception with a set of WWII surplus headphones was really excellent. Then too in 1962 my hearing was a hell of a lot better. :)

No power, no amplification, just a germanium diode and headphones with a good long wire antenna and a cold water pipe.

Ron
 
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