Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Sun 02, 2022 9:58 am


All times are UTC





Post New Topic Post Reply  [ 17 posts ] 
Author Message
 Post subject: Extremely simple crystal radio
PostPosted: Jul Mon 18, 2022 4:32 pm 
Member

Joined: Dec Wed 22, 2021 7:20 pm
Posts: 97
Location: Sherwood Park, Alberta
How does one build an extremely simple crystal radio? Minimal parts, no breadboard (cardboard can substitute a breadboard), no forms (toilet paper rolls and thread bobbins can substitute forms), minimal amount of wire, no diodes, no crystals (a piezo plate can be salvaged from somewhere most likely), no condensers and I highly doubt I could make a leyden jar but two sheets of foil and paper could suffice and worst of all no soldering iron. It will be the very BASIC definition of a radio receiver.

Now, one may wonder: "In what sort of post-apocalyptic wasteland have you found yourself in?"
Not a wasteland but a third-world country. Croatia to be precise. Other than it's striking natural beauty there's not a whole lot to do for a person who does not indulge in alcohol or opiates. I am currently visiting my grandparents due to grandpas deteriorating health (however he's still holding himself well) and grandpa being a retired radio amateur himself, I want to impress him with my skills. Since the Croatian Kuna is worth not much to say the least, I would like to construct something that is essentially free with minimal components and relatively small. I have access to low impedance headphones or a headphone I should say. Other than that, that's all I have access too.


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Mon 18, 2022 6:55 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 12:00 am
Posts: 5773
Location: Austin TX
I'll bite and I'll help, but before I do, I need you to answer three questions:

How much do you trust the laws of physics?

How absolute are your parts requirements?

How talented a scrounger are you?


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Mon 18, 2022 8:40 pm 
Member

Joined: May Tue 30, 2006 3:46 pm
Posts: 11497
Location: Santa Rosa, CA
May I suggest that you search for plans for a "Foxhole Radio" ? These were built under combat conditions by soldiers in WW II. Not exactly post-apocalyptic, but close.

Image

You will need some kind of headphone. Building a headphone can be done, with a lot of work and patience.

This book should exactly meet your needs. http://www.hpfriedrichs.com/mybooks/votc/bks-votc.htm

He builds everything "from scratch."


Rich


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Tue 19, 2022 4:56 am 
Member

Joined: Jan Sat 25, 2020 4:23 am
Posts: 1180
Location: Colorado Springs, CO 80917
Location: Colorado Springs, CO 80917
For almost all simple crystal radios, you will need a high impedance earphone or headphone.


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Tue 19, 2022 3:33 pm 
Member
User avatar

Joined: Oct Fri 11, 2019 2:03 am
Posts: 165
Location: Seattle, WA
Location: Seattle, WA
When I didn't have access to high impedance headphones in my early teens, I succeeded making crystal radio with using the output transformer of a transistor radio as the matching transformer. Also used the germanium diode and the tuning section (e.g. ferrite bar antenna and tuning capacitor) of the same radio.
The reality is that crystal radios once were the state of the art and a cutting edge technology, no matter how simple they seem nowdays.
At least you have a strong transmitter nearby (540kHz at 2 megawatts from Hungary)


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Tue 19, 2022 3:39 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 12:00 am
Posts: 18297
Location: S. Dartmouth MA USA
I took a look at the sales offering for the book:

http://www.hpfriedrichs.com/mybooks/votc/bks-votc.htm

Seems the headphone/earphone problem have been addressed. The most unlikely sources for a transducer were used... i sorta like the homemade crystal stands too...

_________________
List' & I will Enchant Thine Ear


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Tue 19, 2022 8:11 pm 
Member

Joined: Dec Wed 22, 2021 7:20 pm
Posts: 97
Location: Sherwood Park, Alberta
To Macrohenry,

I trust the laws of physics but I don't trust my skills to utilize them properly. So on a scale of 1 to 10, I would say a comfortable 5. I'm a pretty decent scrounger, most of my projects and experiments using scrounged and salvaged components (including but not limited to: paper condensers, roundy and BED style resistors, wire of questionable quality etc.). I'm pretty absolute on parts. I could, maybe, get my hands on questionable moped ignition coils, even more questionable moped ignition condensers... come to think about it, there is a general parts store not too far from me. A mini Lowes or a tiny Home depot, if you will. I wonder, could you make a detector out of piston rings, coils out of ignition coil wire and some sort of filtering from ignition condensers? But other than the little hardware store, there's not a whole lot more. In fact, there's nothing other than that little store!

A good antenna makes for an excellent crystal set. A good ground is needed as well. This being a post-socialist country, radiators and heating pipes are exposed everywhere. Could a lightning rod be used as an antenna? That would be of great advantage but I'm not sure how I could actually reach one on the side of the building I'm in. As for tools, I have access to the very basic. Screwdrivers, needle nose pliers, wire cutters, various hammers but no multimeter! For something of such simple construction I doubt a multimeter is needed, maybe an ohm-meter at most but one would still be handy.


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Tue 19, 2022 8:41 pm 
Member

Joined: Jan Sat 25, 2020 4:23 am
Posts: 1180
Location: Colorado Springs, CO 80917
Location: Colorado Springs, CO 80917
Quote:
Could a lightning rod be used as an antenna?


!. I think it won't be a good antenna since it's intended to be a low impedance connection to ground. :(
2. I think it won't be a good antenna since lightning isn't conducive to continued radio operation. :shock:


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Tue 19, 2022 8:55 pm 
Member

Joined: Jan Sat 25, 2020 4:23 am
Posts: 1180
Location: Colorado Springs, CO 80917
Location: Colorado Springs, CO 80917
Quote:
coils out of ignition coil wire and some sort of filtering from ignition condensers?


Decent enameled coil wire of different gauges could be scrounged from ignition coils, relays, solenoids, electric motors, buzzers, transformers, TV deflection coils and so on. Ignition condensers might work well for bypass capacitors. Small picofarad capacitors & variable caps can be assembled from metal foil and a variety of insulating material. I've seen air spaced variable caps made from metal plates & threaded rods & nuts & washers. Also variable caps made using sandwiched metal & plastic sheets/discs arranged like larger versions of those tiny transistor radio tuning capacitors.

Someone was going to try using CD discs for such a tuning cap but I never heard how it turned out. There was some concern the disc might use a deposited metal film for the recording medium & that would complicate predicting the resulting capacitance. But CD/DVD packs usually have a clear blank disc (apparently only plastic) on top of the stack when you buy them.

Scrapping parts out of old electronics of any kind is apt to turn up something with potential for re-use.

Did not see that you had a soldering iron or solder to work with. These would be immensely useful to you, in time.


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Wed 20, 2022 11:35 am 
Member

Joined: Dec Wed 22, 2021 7:20 pm
Posts: 97
Location: Sherwood Park, Alberta
Come to think about it... a small piece of dielectric can be salvaged from a lighter. Using a stethoscope, since my grandparents have one laying around, a makeshift headphone can be achieved. Would something like this work?


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Wed 20, 2022 2:54 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 12:00 am
Posts: 5773
Location: Austin TX
You need insulated wire, enough for a coil that meets that meets the specifications that are published widely. Unless you are sitting under a blowtorch station there's no skipping on this. Laws of physics.

Same with antenna. Unless you are close to a station you're gonna need a lot of wire probably at least 50' long and as high as possible for an antenna that will give you any volume at all.

Instead of starting with a weak detector such as piezo lighter elements, I would scrounge an old transistor or diode from a defunct appliance or computer equipment. You need a silicon or better a germanium junction. A transistor can be used as a diode. Once you know the rest of the system is working, then you can substitute a piezo crystal, razor blade or whatever.

You can use your low impedance headphones if you have some sort of matching transformer. Without it you may not know whether you have a working radio or not. That can be scrounged from from an old appliance, camera flash inverter transformer, or anything that has a high turns ratio. Others have successfully used stethoscopes for headphones: they must be used with a high impedance coil assembly.

Here's a radio that works.

http://tompolk.com/crystalradios/cedarcreek.html


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Wed 20, 2022 4:53 pm 
Member
User avatar

Joined: Apr Sat 25, 2015 1:58 am
Posts: 99
Location: Bangalore, India
Here's one.

It's a variant of a 'foxhole radio'.

Image

A pair of sensitive 'balanced armature' headphones, a stainless razor blade, a pencil stub, a 150 feet wire antenna and a good earth connection is all that's required.

Hopefully, a nearby AM radio station may be received.

_________________
https://nandustips.blogspot.com


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Wed 20, 2022 7:15 pm 
Member

Joined: May Tue 30, 2006 3:46 pm
Posts: 11497
Location: Santa Rosa, CA
If you can find a piezoelectric transducer, used to make sounds in computers and appliances, these make excellent headphone elements. The larger the diameter, the better.

Image

Dave Schmarder's website is gone, but he made some excellent phones for crystal sets using piezo discs and hearing protector "ear muffs".

https://www.pinterest.com/pin/electroni ... 492715669/

Rich


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Jul Wed 20, 2022 8:09 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 12:00 am
Posts: 18297
Location: S. Dartmouth MA USA
arianskre wrote:
Come to think about it... a small piece of dielectric can be salvaged from a lighter. Using a stethoscope, since my grandparents have one laying around, a makeshift headphone can be achieved. Would something like this work?
IMHO replace the mechanical diaphragm in the stethoscope with a piezo element.

_________________
List' & I will Enchant Thine Ear


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Aug Thu 11, 2022 6:11 pm 
Member

Joined: Mar Sat 15, 2014 8:22 pm
Posts: 226
If there is any coal about you may find some pyrites that will make a good detector. Wire fences, telephone wires (with a cap between) have been used as aerials, or I think a few turns of wire around the telephone lead in. With an aerial and detector you may be able to hear a station without any tuning. The hardest thing might be the earphone. A low impedance one may work, worth a try.


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Aug Wed 17, 2022 3:19 pm 
Member
User avatar

Joined: Aug Mon 16, 2021 2:25 am
Posts: 329
Location: Lewis & Clark Stomping Grounds, Oregon, USA
Location: Troutdale, OR
To make the most extremely simple crystal radio you are focusing on really only one component - the rectifier.

You still need a loop antenna OR wire antenna (or insulated metal structure), earth ground and high impedance magnetic headphones or a crystal/ceramic piezo earpiece. Every crystal radio needs these.

Barring a mineral crystal or germanium diode, there are many things that could be used as a rectifier. A rusty razor blade (cathode) with pencil lead
wrapped at the end of stiff wire (anode). Or a small piece of oxidized iron with a phosphor bronze wire contact. Poor selectivity and multiple strong locals will likely dominate. But it is a bare bones "radio receiver".

Jeff


Top
 Profile  
 
 Post subject: Re: Extremely simple crystal radio
PostPosted: Sep Tue 06, 2022 9:56 am 
Member

Joined: Sep Tue 06, 2022 8:59 am
Posts: 41
Location: Melbourne Australia
The simplest Xtal set is just a Germanium diode connected between an antenna and ground with some headphones across it.
If you have only 1 loud radio station nearby you'll hear it.


Top
 Profile  
 
Post New Topic Post Reply  [ 17 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 7 guests



Search for:
Jump to:  




































Privacy Policy :: Powered by phpBB