Foxhole Radio Headphones

I have completed a "foxhole" radio as an experiment. I tried using a little white earbud that came with an old transistor radio. I can get nothing except the faintest hum that Superman would have to strain to hear if it's right next to my computer monitor. I took it all outside and hooked it up. No nothing at all. Good ground, good antenna, etc.
Am I using an earbud of the wrong type? What should I be using? Is there something more sensitive that has a better output or volume?
I know that my wiring is all correct because I can move the graphite to the honed edge of the razor blade (antique Schick blue blade) and I hit the sweet spot and get that faint hum from my monitor.
Thanks
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Most earbuds I have seen are low impedance. To work with a crystal or foxhole radio, you need a high impedance headphone.
(Connoisseur of the cold 807) CW forever!
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I used to put a 47K resistor across the 2 earphone connects.
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Those are not sensitive enough either. Try a crystal earphone.
They go for about $1.
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I built a foxhole radio when I was 8 years old and it worked, so don't give up!
The headphones I used were high impedance magnetic Cannonball brand, as used to be available everywhere (but not anymore.) I probably could have done better with a crystal headphone set (harder to come by.) In the 1960's, those little white plastic earplug headphones which came with pocket transistor radios were crystal, but the modern stereo earbuds seem to be low-impedance magnetic and they won't work. The most important thing is that the headphones be high impedance.
A good ground and a long antenna will help. Not to mention keeping it away from a noise source like a monitor-computer combo or a TV set.
The foxhole radio was something created by GI's in forward areas in WWII. The typical headphones available were the U.S. high impedance magnetic style as used in B-17's and other aircraft. It's a classic example of improvising something useful from almost nothing.
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Well, I am sure glad to hear that someone had success at age 8 with a foxhole radio! I was also eight years old and tried making one for a school Science Fair project. It was a genuine flop and it left bad scars on me that last to this day, 52 years later about foxhole radios.
(Connoisseur of the cold 807) CW forever!
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Fredro, et al...
Interesting experiences related so far...
My experience was similar, but at about age 10...A used razor blade compliments of my father and a hand-wound coil of about 50 turns of 18awg magnet wire with a slider of thin metal stock proved to be just so-so with respect to performance when hooked to a 110 foot longwire up feet and an earth ground outside my bedroom window...Headphones were 2K ohms as purchased with my Knight Kit CPO from Allied Radio...One station only (WKBW, 50kw at 1520 kc ) no matter where the slider was positioned on the coil...A brief discussion with the neighbor across the stree who was an electronics tech resulted in my winding a "real coil" of several hundred turns using smaller gauge magnet wire which brought one or two more stations but WKBW still was there now as QRM to the others...Later, a 1134 diode replaced the razor blade detector with improved reliability but I was disappointed with the same poor selectivity.
Gee, Curt...I hope your remarks of having left "bad scars that last on me to this day" are to be taken as tongue-in-cheek.
FWIW
Bruce
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Nope, I have had a disdain for foxhole radios and crystal radios in general ever since then.
(Connoisseur of the cold 807) CW forever!
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Curt:
For optimum Q and, of course sensitivity, you need to wind a coil on a Quaker Oats box. I bet you did not know that...
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if using a oats box make a slider with a wood dowel rod the lenght of box prefer 1/4 inch dia as long as you need then need a 1/2 piece of dowel about 1 inch long with 1/4 hole to slide down the long dowel rod incert a brass tack to make slider contact hook wire to slider brass tack wooks good , I could post a picture if needed
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As I recall, blue Personna razor blades worked best. I knew nothing about coils and just scramble-wound a bunch of wire onto a cardboard tube formerly used for paper towels. The wire was old enameled stuff from the yoke of a junk TV set I found at the curb somewhere. I only got one station, but that's all I expected.
Don't expect sound to come blasting out of the headphones, unless you are in the near-field of an AM broadcast station. The success of this radio more or less depends on pretty decent field strength of something in your area.
By the way, some newer razor blades seem to be coated and will not work very well if at all.
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Yeah, I know and knew all about the Quaker Oats coil forms.
I now know why my set was a failure, but what the heck did I know when I was only eight years old? I wound the coil with close fitting turns without any spacing and I used bare wire, so the whole coil was one big mass of shorted turns. Heck, the transmitter of the ham who lived next door had bare wire coils that plugged in. But they were space wound, idiot!
But still it hurt me so bad when I put so much work into that set, even varnishing the board. I must have worked on it for a good month and all went down the drain. They did give me an "E" for effort, however.
(Connoisseur of the cold 807) CW forever!
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Curt, did you get the plan from a Cub Scout book? I did the same thing about 50 years ago but seems that the blade I used was a bronze color. Worked as well as yours. Someone said that a rusty blade would work better but never tried it. B
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The plans for mine were in a book in my elementary school library. I believe the title was something like "All About Radio and Television." I must have checked it out enough times that one summer after we had moved and I was in another school, the librarian called my parents to announce that the book had gone missing and I must somehow be responsible (even though I wasn't.)
I can also recall my father storming into breakfast one morning announcing "Who the @#$% took my razor blade?"
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The only crystal radio I ever played with as a kid was a "rocket radio". This was a red plastic thing shaped like a 50s/60s spaceship rocket. I lived in northern West Virginia at the time, and all I could get was WWVA booming in (50,000 watts Country music). The station I wanted to get I could never get. I remember clipping the antenna alligator clip to my bed springs and listening at night.
Good times.
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I stoped counting my Failures when I ran out of fingers and toes one reason hard for me to count much higher
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B- I read up on the foxhole radio in the same book that Geoff mentioned, All About Radio & Television. Mom had subscribed to them for me and my younger sister. We ended up getting close to fifteen books of the series. My favorite was this issue, where my younger sister liked Strange Beasts of the Past the best.
(Connoisseur of the cold 807) CW forever!
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Well I am now not 100% sure where I found the plan, but see one difference. Mine said to remove the lead from the wood and wrap copper wire around it. I think I used some "varnished" wire from an old coil. No where did it say clean wire! B
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You can get crystal earphones for about $3.50 on the Internet. You need the piezo type.
Radio Shack sells piezo units for $2 or $3, I believe.
Also, you can use the little noise or music discs for greeting cards for an earphone. Just get rid of the tiny "circuit board" and keep the disc part with the two wires.