Tinkering with the Credit Card Crystal Radio


A few weeks ago, we published a short post about a credit card crystal radio from an eBay seller in the UK.

I purchased a kit–at $17-18 US shipped, it’s quite a modest investment for what might be a fun little project.


The crystal radio arrived while I was traveling during Easter break, but my free time has been so (extremely) limited lately, I was only able to unpack and try out this new arrival yesterday.


The biggest surprise for me was the fact that this isn’t really a kit–the board is fully populated and requires no soldering whatsoever. The board feels of very good quality.

All that is required is connecting the high-impedance earphone, earth/ground and aerial/antenna to the board. Since all of these components can be connected with the supplied alligator clip cables, getting it on the air took all of 20 seconds. I simply hooked up the ground and connected the aerial to my sky loop wire antenna.

I instantly heard a signal and station ID which confirmed it was our closest local broadcaster on 1010 kHz.  This station isn’t of the blowtorch variety, but is the strongest one I receive on the MW band simply due to its proximity. Audio was quite faint through the earpiece, but I believe if I tinkered with antenna length and the two variable capacitors, I could improve reception.

SWLing Post reader, Richard Langley, received his crystal radio and had a very similar experience with reception.


With any crystal radio (especially one this small), performance is directly correlated with antenna length, availability of a good ground connection and, of course, strong broadcasters in your vicinity.

I plan to spend an evening tinkering with this little receiver and see if I can pick up some of the night time powerhouse AM stations on the east coast.

I can say this: if you’re looking for a simple, uber-compact emergency receiver for your go-bag, bug out bag or emergency kit, this one will certainly fit the bill. This crystal receiver and all of its components weight no more than a few ounces and could easily fit in compact pouch or sleeve.

Have any other readers have enjoyed tinkering with this little emergency crystal radio?

If you would like to purchase one, try searching eBay with one of the links below. The product will only appear in the search results if currently available.

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7 thoughts on “Tinkering with the Credit Card Crystal Radio

  1. mr bill

    rather novel since the last time i tuned a crystal was using a safety pin, crystal and red seal headphones to get a science badge for scouts. My rat of a scoutmaster didn’t believe it worked so i buggered off and became what i am without his approval. I’ll buy one of these to represent the calmer minority in these threads. Life is too short to be a Democrat.

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  3. Radio

    As the guys at TheRadioBoard have pointed out, it’s a pretty wacky Crystal Set.

    The way that the PCB coil is laid out makes it more like a non-inductive resistor that an Inductor. It would only be the small molded choke which provides inductance.

    Plus the two trimmer capacitors are simply in parallel, so are fairly redundant.

    As per the folks on TRB say, it would barely tune the top of the Broadcast band.


  4. Guy Teague

    i received mine day-before-yesterday and so far am unable to hear any signal, only the faintest of static noise. i did test the earphone as the instructions suggested and i moved the supplied antenna back and forth between /earth/ and /aerial/.

    only after i connected my 21′ reel-up antenna and to /aerial/ and /earth/ to a negative power supply jack did i get some faint static noise. i live 15 miles from town and i didn’t try outside.

    i remember having these when i was very young and what we did was hook up the antenna or ground connection to the metal ‘dial stop’ of a rotary telephone (gotta be a certain age to remember that!) or to an outside faucet.

    /guy (73 de kg5vt | wqpz784)

  5. Dave NM0S

    Fascinating! It doesn’t take much to make a crystal receiver, and this one looks very nicely done. Thanks for the review. – 73


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