Listening to Radio with NO Radio? - Page 1
Forum section: electronics / beginners

author: Larsson55
author_rank: Regular Contributor
timestamp: February 16, 2025, 08:38:36 pm
content: Back in the early 50's in Europe I remember a contraption I made when I was a kid to listen to the radio.Europe was then recovering from the war and everything was not easy to find so I don't remember where the idea came from and how I got what I had but I remember I had on a small pc of wood a small speaker, a "stone" and a small battery along with some wiring and poking the stone with the end of a wire in different places I could listen to radio stations.I would have liked to replicate this contraption but have no clue what this "stone" was and the wiring. I remember the stone was gray and shinny with sharp edges about the size fitting in the palm of your hand. Any ideas?Thanks

author: coppercone2
author_rank: Super Contributor
timestamp: February 16, 2025, 08:42:54 pm
content: a galena crystal?

author: Analog Kid
author_rank: Super Contributor
timestamp: February 16, 2025, 08:45:18 pm
content: Yepper. The OP has just described the canonical crystal radio.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 16, 2025, 11:26:18 pm
content: "Foxhole" radio?Here's Google AI, "A foxhole radio was a makeshift crystal radio that soldiers used in World War II to listen to the radio. Soldiers built them because vacuum tube radios could be detected by the enemy.How it workedA safety razor blade was used as the radio wave detectorA wire, safety pin, or graphite pencil lead acted as the cat's whisker..."Another Google AI, that's not a safety razor blade. WWII were real razor blades.

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 01:52:25 am
content: Many thanks folks, never thought anyone would know what I was talking about but I'm very happy now I now what this radio is called "Galena" and I will try to make one again

author: Analog Kid
author_rank: Super Contributor
timestamp: February 17, 2025, 01:56:53 am
content: Well, it's usually known by the generic term of "crystal radio". The crystal could be galena (lead sulfide). More modren versions used a germanium diode (1N34).I built a crystal set back in the 1960s but never got it to work. (I think the coil was wound on a toilet paper tube.) Maybe time to revisit that project; it'd be pretty kewl to actually hear a radio transmission with a totally passive circuit.

author: Analog Kid
author_rank: Super Contributor
timestamp: February 17, 2025, 02:04:53 am
content: Here's a page with a lot of crystal radio set advice and designs:https://qsl.net/ve7sl/crystal.htmlThey even have contests for "bagging" the most stations (ham radio frequencies).

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 03:23:23 am
content: Quote from: Analog Kid on February 17, 2025, 02:04:53 amThanks for your time mate, very interesting and useful links however looking at the schematics they all have electronic parts which were not available in the 50's Europe when I built mine so I wonder how mine worked. Perhaps since we did not have high rise buildings and radio stations were not many? I will start making a list of what I need

author: Analog Kid
author_rank: Super Contributor
timestamp: February 17, 2025, 03:43:27 am
content: You could probably replicate what you did back then with any of the simple circuits (coil + capacitor + diode + earphone) using a galena crystal as the diode, which you should be able to find at a gem store, with a wire "whisker" to find the right spot on it.

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 04:17:40 am
content: Quote from: Analog Kid on February 17, 2025, 03:43:27 amIts a good start, thanks

author: MK14
author_rank: Super Contributor
timestamp: February 17, 2025, 04:30:56 am
content: Quote from: Larsson55 on February 16, 2025, 08:38:36 pmSounds a bit like the following book, but the book maybe too recent, to be what you originally referred to, in the 1950s.https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Making-a-Transistor-Radio-Ladybird%20Books-1972.pdf

author: Analog Kid
author_rank: Super Contributor
timestamp: February 17, 2025, 04:32:56 am
content: No, that's completely different. The Ladybird radio is an active radio receiver, with transistors and all.What we're talking about here are completely passive radio (i.e., no power source or active devices).

author: MK14
author_rank: Super Contributor
timestamp: February 17, 2025, 04:36:44 am
content: Quote from: Analog Kid on February 17, 2025, 04:32:56 amNo, it includes fully passive (+diode), crystal set ones, as well.E.g. Page 12 + 26.

author: Aldo22
author_rank: Super Contributor
timestamp: February 17, 2025, 07:51:45 am
content: https://en.wikipedia.org/wiki/Crystal_radio

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 08:48:32 am
content: Thank you MK14 for the wonderful Ladybird Book, it is what I need. I don't have much experience in electronics so this .PDF provides all the details I need to buy what I need and easy to understand schematicsAldo22 thanks for the Wiki link, very interesting

author: Terry Bites
author_rank: Super Contributor
timestamp: February 17, 2025, 09:04:21 am
content: https://en.wikipedia.org/wiki/Crystal_detector

author: u666sa
author_rank: Frequent Contributor
timestamp: February 17, 2025, 09:45:12 am
content: The only question is what you going to listen to, no more long waves.The new crystal radio called Si4732. 1 chip and you got access to pretty much all of it FM and bellow.

author: langwadt
author_rank: Super Contributor
timestamp: February 17, 2025, 10:10:42 am
content: http://www.oh3ac.fi/Foxhole_Radio.pdf

author: stretchyman
author_rank: Regular Contributor
timestamp: February 17, 2025, 10:14:04 am
content: Well...an SDR doesn't look much like a 'Radio'.Prob best to use one of those!Str.

author: ME
author_rank: Frequent Contributor
timestamp: February 17, 2025, 10:59:54 am
content: I made my first xtal radio from that same book!,was in about 1973,used the sink cold water tap as earth, could only get bbc radio 3 tho as it was at daventry about 7 miles away.

author: coppercone2
author_rank: Super Contributor
timestamp: February 17, 2025, 11:10:12 am
content: maybe they should bring back long wave because its a human right to wind a coat hanger and press it into a rock to pick up the newsthere was no technocrat behind access for that one . but they also end up taxing you for living nearby lmfao

author: mikerj
author_rank: Super Contributor
timestamp: February 17, 2025, 11:27:01 am
content: Quote from: ME on February 17, 2025, 10:59:54 amYep, I discovered the benefit of a good ground very quickly when I built the crystal radio in the Ladybird book at about 10 yo, it makes a huge difference. I still have that book somewhere.

author: Retep
author_rank: Regular Contributor
timestamp: February 17, 2025, 12:51:02 pm
content: Quote from: u666sa on February 17, 2025, 09:45:12 amWhere I live even on the medium wave there is nothing to listen to, unless you enjoy listening to interference produced by modern day electronics (smps, solar-inverters...etc.).

author: MrAl
author_rank: Super Contributor
timestamp: February 17, 2025, 01:10:35 pm
content: Quote from: Larsson55 on February 16, 2025, 08:38:36 pmThe main idea behind these 'radios' is the creation of a home made diode, and a high impedance headphone.The diode can act as a detector for AM transmissions and the headphone is used so you can hear the resulting audio. You do not even need a battery.The simplest one I think is to get a piece of rusty steel. It has to be rusty because the iron oxide becomes part of the diode junction.You then use a steel sewing pin and have the point gently touching the rusty steel. That creates a point contact diode. You have to have a way to adjust the pressure of the point onto the steel so you would bend the needle and adjust the pressure with a non-conductive mount mechanism that allowed you to move the needle a little.The headphones are connected to the steel substrate and the sewing pin. They have to be high impedance headphones or one of those little earphones that sticks in your ear (also has to be high impedance).The audio is not loud but you can still hear nearby stations.Last time I made one of these was over 40 years ago.

author: Aldo22
author_rank: Super Contributor
timestamp: February 17, 2025, 01:11:36 pm
content: Quote from: Retep on February 17, 2025, 12:51:02 pmIn the worst case, you can listen to your signal generator.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: February 17, 2025, 01:51:15 pm
content: To add to Mr AL post:This is US Stuff, but it may give you some ideas. Here is an ebay link. There is a Philmore cat whisker Xtal detector that is kinda what you are describing. We do not know where you are, there may be other sources in your area.https://www.ebay.com/sch/i.html?_nkw=crystal+radio&_sacat=0&_from=R40&_trksid=p4432023.m570.l1313Here is an article about a crystal radio that uses an already assembled diode. Regular relatively modern detector diode.https://www.arrl.org/files/file/Technology/tis/info/pdf/129756.pdfThe old Galena crystal is just a diode, although much cooler. Other things like a rusty safety razor blade (not stainless) were used by creative people as the detector diode. .The headphones must be very high impedance, as mentioned in the ARRL article, these high impedance headphones are essentially crystal or ceramic transducers that are not common anymore but can be found for almost nothing at Hamfests...A High impedance ceramic microphone would probably work for the headphone, These are cheap and easily available. They are just a high impedance ceramic transducer, which is much like a crystal mic or crystal headphone. The little old transistor radios came with one high impedance earpiece also.You also need a long antenna and a good ground.We still have broadcast band AM here in US, this is what the xtal radios can receive, they need a good strong signal.

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 05:26:37 pm
content: Quote from: langwadt on February 17, 2025, 10:10:42 amAnother excellent read, many thanks

author: 807
author_rank: Frequent Contributor
timestamp: February 17, 2025, 05:45:13 pm
content: Building a crystal radio at school is what started me off on my electronics career & hobby around 50 years ago. A coil wound on a ferrite rod, a nice big air spaced variable capacitor, a germanium diode, a resistor, and a crystal earpiece, along with plenty of wire for the aerial & a connection to the earthed water pipes. I was amazed that I had actually built a radio capable of picking up MW stations. From then on, I was hooked.The same type of crystal earpieces are still readily available today. Sadly, large air spaced variable capacitors are very expensive nowadays, that is if you can find one at all. What I did when I built one at home, was to replace the variable capacitor with a fixed value capacitor & wrap some paper round the ferrite rod before winding the coil. Then the ferrite could be slid up & down the winding, changing the frequency.

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 06:06:02 pm
content: Is there any place on the Internet which sells a complete kit for a crystal radio? In my area there are no stores to buy any part required so I will have to buy everything individually which gets confusing and prone to mistakes.

author: JohnG
author_rank: Frequent Contributor
timestamp: February 17, 2025, 06:28:56 pm
content: Take a look at this, starting with Chapter 6:https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/The-Boy's-First-Book-of-Radio-Morgan-1954.pdfJohn

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: February 17, 2025, 06:56:46 pm
content: Quote from: Larsson55 onTodayat 06:06:02 pm

author: Stray Electron
author_rank: Super Contributor
timestamp: February 17, 2025, 06:58:16 pm
content: Quote from: Analog Kid on February 17, 2025, 01:56:53 amI built one in the 1960s as well. I followed the directions that were in the old Boy Scouts handbook and it worked perfectly. They used a pasteboard Quaker Oats container IIRC. I currently have a crystal radio set for display that has an actual Galena crystal and a safety pin for the probe and it's a real PITA to use. You can to keep fracturing of pieces of the crystal so that you have a fresh surface for the probe's contact point. But the trouble is that the surface will oxidize so you need to keep moving the probe around to get a good contact; and eventually you have create a new surface on the crystal. A 1N914 diode works much better but isn't as authentic. Today I expect that there might be better choices for the diode but they've used 1N914s since at least the 1960s.Since there is no amplifier in a crystal radio it's important to use high efficiency headphones.

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 07:16:08 pm
content: Quote from: JohnG on February 17, 2025, 06:28:56 pmThank you John, an excellent book to read

author: Larsson55
author_rank: Regular Contributor
timestamp: February 17, 2025, 07:19:14 pm
content: Quote from: Wallace Gasiewicz on February 17, 2025, 06:56:46 pmThis search gave me what I need, many thanks

author: 807
author_rank: Frequent Contributor
timestamp: February 17, 2025, 09:15:43 pm
content: Quote from: Stray Electron on February 17, 2025, 06:58:16 pmI'm sure I tried silicon diodes such as the 1N914 in the past, but was met with silence. I could only ever get germanium diodes to work. As genuine point contact germanium are hard to get these days, I've read that Schottky diodes such as BAT85 will work.

author: BrianHG
author_rank: Super Contributor
timestamp: February 17, 2025, 09:20:11 pm
content: Quote from: 807 on February 17, 2025, 09:15:43 pmForward biasing a 1N914 with a 1.5v battery and a high value series resistor would probably get it to work. Tune the resistor value right and it will outperform a germanium diode. Though, forward biasing a germanium diode will also improve it's performance.

author: 807
author_rank: Frequent Contributor
timestamp: February 17, 2025, 09:27:51 pm
content: Quote from: BrianHG on February 17, 2025, 09:20:11 pmOh yes. There are ways of getting round the higher forward voltage drop of silicon diodes, but for an unpowered crystal set with zero running costs, a germanium diode is needed for maximum sensitivity.

author: MrAl
author_rank: Super Contributor
timestamp: February 19, 2025, 04:30:05 pm
content: Quote from: Wallace Gasiewicz on February 17, 2025, 01:51:15 pmThat's very interesting. I have not heard any mention of "Fahnestock Clips" in a very long time. Forgot they even existed