Crystal radio kit, need some help figuring out how it works

[vortalexfan]

Hello everyone, today my uncle brought down with him from Michigan where he lives an old Crystal kit Radio that he and his uncle (who passed away back in the late 1970s) had built together shortly before he passed away, and I'm trying to see if I can get it going for him again, it has what appears to be an old Germaniun signal diode in the radio's circuit (that acts as the "crystal" in the circuit) and the diode is unfortunately dead, and also I can't seem to figure out how the set is supposed to get power (what type of battery and what the voltage should be.)

If any of you guys recognize the radio design (if it was a design from something like an old Radio Shack magazine or some other electronics magazine from that time period) then it would be much appreciated if you could share any information with me about how this radio is supposed to work and what kinds of signal diodes could be used in this radio and what I could used as a power source if one is needed.

See Pictures below.

[Ed in Tx]

No battery needed. You just need a good ground, RF from an antenna, and high impedance headphones or an earphone. Those are the 4 connections it has. Power is from the rectified RF. And of course replace the bad diode if it is indeed bad.

[vortalexfan]

Originally Posted by Ed in Tx

No battery needed. You just need a good ground, RF from an antenna, and high impedance headphones or an earphone. Those are the 4 connections it has. Power is from the rectified RF. And of course replace the bad diode if it is indeed bad.

OK, thanks. What kind of diode should I use in this thing? The original one looked like an old Germanium signal diode, like what is used in old TVs and Radios.

[Ed in Tx]

Yep, a germanium diode. They rectify as low as .2 Volts. (Compared to silicon .6V)

[jr_tech]

Simple Boy Scout radio and improvements:

https://m.youtube.com/watch?v=mubvsqFrE88

jr

[vortalexfan]

Originally Posted by Ed in Tx

Yep, a germanium diode. They rectify as low as .2 Volts. (Compared to silicon .6V)

I think I might have some diodes that might work in this radio, but I'm not sure.

I just looked over at AES and they had 6 signal diodes listed there for sale, 3 of them of the Germanium variety (1N34A, 1N60, and 1N270) and 3 of the Silicon variety (1N4148A, 1N914, and 1N4448) and I'm curious as to which one of those would work best in this application, also I'm wondering where I might find some high impedance headphones like what this would use, or if this might even work with a high impedance speaker like the type used on the old 1920s radios used?

[Electronic M]

I would go with Germanium, or low voltage Shottkey diodes. You want the lowest forward voltage drop diodes you can get.

[vortalexfan]

Originally Posted by Electronic M

I would go with Germanium, or low voltage Shottkey diodes. You want the lowest forward voltage drop diodes you can get.

OK, so I'll order a few of the 1N34A, 1N60 and 1N270 Germanium diodes, and see which ones work best, and also try some 1N5158 and BAT41 Schottkey Diodes as well (they're only 10 to 15 cents a piece so they won't break the bank to buy about 10 or so of each type.)

[jr_tech]

“I'm wondering where I might find some high impedance headphones like what this would use“
High impedance earphone :
https://www.tubesandmore.com/product...72a919c913a972

jr

[Jeffhs]

Originally Posted by Ed in Tx

No battery needed. You just need a good ground, RF from an antenna, and high impedance headphones or an earphone. Those are the 4 connections it has. Power is from the rectified RF. And of course replace the bad diode if it is indeed bad.

Crystal sets require a very strong signal, otherwise you will not hear anything. (I've had several and every one of them only received one station, a 500-watt local station about two miles away from where I lived at the time.) I don't know if the OP is near any very strong radio stations in northern Indiana, but if not, the radio absolutely will not work. Northern Indiana is close to Chicago, which has many 50kW AM radio stations, but I don't know just exactly how strong any of those stations would be in that section of Indiana. The crystal radio might work in the immediate Chicago area, but again, not knowing the geography of the northern Indiana area other than it is within a short distance of Chicago (I live in northeastern Ohio and have never been to Indiana in my life), I don't know how strong those stations would be where the OP is located.

BTW, I agree with Ed in TX about the diode used in crystal sets to rectify the received signal. If this diode is in fact defective (or installed backwards), of course the radio will not operate at all.

[old_tv_nut]

If the diode is installed backwards, the only result should be that the audio signal polarity will be inverted.

Did anyone mention that you need a long wire antenna, like on the order of 30-50 feet?

[old_tv_nut]

I also wonder how bad the local interference will be these days from fluorescent/LED lamps, other electronic gear, etc. Not sure how different the long wire antenna interference pickup will be compared to a regular AM radio.

[madlabs]

As to recognizing the design, it is the very simplest possible crystal radio. As pointed out, it will only pick up strong local stations. If you look on the net you will find many variants, some of which are pretty sensitive. I built quite a few crystals sets and some of the more sophisticated designs work pretty well.

[vortalexfan]

I can get WLS from Chicago in where I live, during the day and During the Night, I can also get WOWO out of Fort Wayne, Indiana where I live, I can also get WLW out of Cincinatti, Ohio really well in the evening and fairly well during the day, and I can get WGN out of Chicago really well during the day and night, as well where I live. Just to give you an idea of the stations I can get in where I live on the AM Dial, all of the Aforementioned stations are 50kW stations.

[vortalexfan]

Originally Posted by old_tv_nut

If the diode is installed backwards, the only result should be that the audio signal polarity will be inverted.

Did anyone mention that you need a long wire antenna, like on the order of 30-50 feet?

I have 3 top-hat style germanium signal diodes that according to my diode check on my DMM are still good, but I have no idea how to tell which way is the anode and which way is the cathode (they aren't marked.)