Make Razor Blade Diode for Crystal Radio/Foxhole Radio

How to make a razor blade diode for a crystal radio/foxhole radio. This involves using a pencil and a slightly modified razor blade to make a diode to use in place of a germanium diode. To modify the razor blade, heat it with a propane torch or the flame from a gas stove until part of it has a bluish color. This is a coating of iron oxide which acts as a semiconductor for the diode. Connect the uncoated end to the earpiece and the coated end to the coil, and capacitor if you have one.

To see how to make the crystal radio in this video, watch "How to Make/Build a Crystal Radio":

To see how to make the earpiece amplifier shown in the video, watch "How to Make Amplifier for Crystal Radio Earpiece":

To see details of how a crystal radio works, watch "How a Crystal Radio Works":

To see how to make your own crystal earpiece like the one in this video, watch "Make Crystal Earphone/Earpiece for Crystal Radio - Homemade":

For a better amplifier, one that plays on a loud speaker, see "How to Make Crystal Radio Amplifier for Speaker":

Follow behind-the-scenes on:

Music used at beginning and middle:
Licensed under Creative Commons: By Attribution 3.0
ISRC: USUAN1100873

Music used at the end:
Maraton Man

[tehcno]

everything is fun..but when nothing works ...it feels like throwing everything out of the window!!!your answer makes me realise that i have a lot to learn! thankyou!

[David-hmic]

To truly blue steel you need to start with carbon steel. It's very hard to find a carbon steel double edged razor blade these days but carbon steel single edged blades are plentiful at any hardware store. Yours turned gray because you went way above the temperature to make it blue and that applies whether carbon or stainless. A solution of salt, vinegar and hydrogen peroxide can be used to rust carbon steel. After it's rusted, place it in boiling water for a few minutes and polish with steel wool. Use only steel wool. Brass or stainless substitutes will interfere with the process. Repeat as necessary to get a good rust blue formed.

[BixLives]

5 and 9!

Good job, lad. After seeing so many supposed graphite/steel detector radios that are missing the tickler pencil or coils so they are not tune-able, etc., YOU are the only one, so far, that I found has got it RIGHT. Congrats!

If done properly (an oatmeal box makes a slightly better coil form), they are quite tune-able with fine selection, however, less powerful than a galena set, . In fact, if you substitute a simple modern glass (crystal) diode, you will be able to receive stations from many miles further away. Also, you can power a full Westinghouse set of carbon headphones. (I have a nice set of head phones with bake-lite "ear pads" that sound great even though they are from ca. 1918. (they are a tad uncomfortable!) Even the old cloth wires & simple plug ends. Hets and super hets with triodes and even class A-B amplification were in use by the early 1920s,

The hi-fi craze could have gotten started much earlier as radio stations of the 1930s transmitted modulation of far better fidelity than the AM broadcast band has today. That's the drag of having old radios...—nothing to listen to...

I have been a HAM for 45 years. I did not always use the HAM bands, however, er, um sometimes I used the 3 meter band or the 180 metre band (with a Marconi aerial) so my mates could have fun playing their favourite records for the town. But 3 meters FM was far easier and cheaper to build and resonate. I used two Radio Shack FM dipoles as stacked bays ans built my own balun and matching transformers with simple coax loops. We put out about 15 - 20 watts (all tubes back then -no PLL chips). I used a simple phase modulation FM method that sounded better than the regular stations because I, er, um, might have been exceeding 75 kHz deviation and perhaps there might have been some AM components in the modulation. But we had better bass than any other station on the band! Since we had no money, it was a great way to sound good without an Optimod! I was able to get some sample optical isolators (for free) and make a fair compressor-limiter. Parts were as near as the next TV set or old radio thrown out on the kerb!

Resourcefulness is my favourite thing about being a HAM.

73s !

[oceanbreze]

A similar option is a utility blade which is thicker. I heated one on an electric stove and it seemed to get some blue coating on it. I tested this diode with the diode checker in a multi-meter and it has one if the lowest forward voltage drops available, at about 0.2v. I guess it is a type of Schottky diode.

[harleyblue]

i made my first one in 1964 from a diode an old pencil and in those days an Ear aid only picked up the light wave broadcast
but it still works after all these years.not even a battery required.thumbs up.

[tehcno]

thats what i call 1-2 hours of hardwork fiddling with 3 types of problems....and you dont get annoyed....ii have to salute you !!thank you!

[RimstarOrg]

Jeri has so many great tutorials, I'm always discovering more!

[RimstarOrg]

How can I get annoyed when it's fun! Though you have to remember when to get stumped, to move onto something else for a while. I'm glad you enjoyed it. Thanks.

[RimstarOrg]

I agree. It's always sad to see simpler technologies or materials vanish, to be replaced by more complex technologies and harder to get materials. There are pros and cons though. The new stuff makes it easier to take things to another level, but there's lots of fun and education playing around with the basics, and as you point out, can be necessary. I've seen it happen many times.

[RimstarOrg]

Yeah, I'm the same way. I find it enjoyable watching videos on how things are made too. I'm glad you're enjoying mine. Thanks for watching!

[TheKingofRandom]

This is useful information. A razor blade and pencil is easier to find than a germanium diode. Do you think this would work with any thin piece of steel?

[notfastuc]

I may never make one But I enjoy watching your videos showing how they are made

[ronb]

Fox hole radio. I made one using a lead from a number 2 pencil. Then I tried a lead from a capacitor in which I could pick up more than one station. KDKA wad the first but I also picked up a weaker station KQV in Pittsburgh. Good project for a pre teen I was in the seventh grade when I read how to make thos radio. You can use an old dark penny instead of a razor blade.i also picked up short Wave station from the Netherlands probably because my coil was big and over 100 turns. The corrosion of the penny had something to do with the reception. 73

[RimstarOrg]

A foxhole radio is a crystal radio but there are many, many different possible circuits for crystal radios. I'd always considered foxhole radio type crystal radios to be the ones that were used in the foxholes. My understanding is they were tunable using the razor blade diode and possibly the length of the antenna. My crystal radio in this video is tunable via the tuning coil, variable capacitor and the razor blade diode.

[daviddavidson]

Apparently a razor blade diode was used in the radio made at the Hanoi Hilton POW camp. I think a slinky spring was used as the coil and foil and paper for a capacitor.

[RimstarOrg]

Thanks, man! The slight differences in focus between Grant's and my channel had me wondering, so I'm glad to hear it. Thanks for letting me know.

[RimstarOrg]

I don't know yet. :) It seems everything has multiple uses! I'm glad you enjoyed the video.

[RimstarOrg]

Nice. Lots of good variety of loop antennas you've done there.

[thanthanasiszamp]

I like your demostration RimstarOrg, especially the part with the razor blade diode.

[RimstarOrg]

You're welcome, Thomas. I'm glad you found it so.