Jools' Razor Blade Crystal Radio

Foxhole Radio

Jool's razor blade crystal radio

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I am strictly a 'newby' in that my speciality is foxhole radios. If you might be interested in those, I have a whole load of photos of various contraptions I have built that work with razor blades and such like. I wanted to get right back to the beginning of the science and have been successful in building sets that work with a collection of household items.

I believe that the magic begins with the core science, and when you hear music and voices coming through on a set made from the contents of a kitchen drawer, it makes you realise how amazing the whole genre is.

In time, as I get the mechanical ability to make more 'beautiful' radios I will take more photos.

I am not a ham radio member, but I have been a 'commercial radio' broadcaster / presenter. So, I'm a bit of an oddball,

Jool's razor blade crystal radio   Jool's razor blade crystal radio

You can see from the schematic that it's based on a 1920's design and is a very basic design. However, with the variable coil wired into the aerial, there is a fair degree of tuning available however, the local BBC station is pretty dominant throughout as I only live about two miles away from their main transmitter. I took a 'short cut' route by linking the aerial wire directly into the roof TV aerial socket (not a particularly safe idea, don't try this at home) and got a surprisingly good, interference-free sound.

The audio quality is slightly sibilant but on the whole, very listenable. I uploaded a couple of sound files to demonstrate just how clear the sound is - Sound File 1   Sound File 2 I emailed the show and the DJ gave me a name check, just to prove it was working.

In terms of construction, I used things I could find in my shed (a cheeseboard, nuts, bolts, brackets, door handles) and the whole thing took about two days to complete. The only tools required were: a drill, a soldering iron, a screwdriver set, a pair of pointed pliers and a pair of scissors.

The luckiest find was a pack of 'Gillette Blue' razor blades which I picked up at a car boot sale for fifty pence, but I found it very hard to locate the 'sweet spot' (which was usually on or around the lettering) so I eventually used a rusty blade from my dad's old shaver. This worked best when one contact (the mounting post) was linked directly to the flat rusty surface and the 'cat's whisker' (a brass safety pin) touched the blade edge. This arrangement worked perfectly at any point along the blade so long as a tight contact was made. Other references describe using the point of a hard pencil 'lead' mounted on the safety pin as the contact point but I found this to be not only fiddly but quite ineffective (and the lead kept breaking).

I mounted it with a standard headphone socket so that my daughter could play it through her computer (and so I could make recordings of the various tests and programmes I heard). That was a decision of convenience.

I don't have a website dedicated to radios, but I am a writer and in the middle of a novel about a radio star from the 40s and 50s. The best link (if at all) to use would be to the hub of that creative pursuit - http://www.kooshrecords.co.uk/reg/ Also - happy to show this email address as a contact.

As I get chance to take other photos of these 'foxhole' radios, I'll send them over for your perusal. There's some 'wacky' stuff! I hope you like the 'enthusiasm' and boy scout innocence inherent in these designs (which was my intention: to make a device capable of hearing radio without any deep scientific knowledge, skills, equipment or resources. The kind of radios that boys in the 20s would have made.)

Best regards
Jools
jools@bramwellslater.org

Jool's razor blade crystal radio

Close Up View of the Detector



Jool's razor blade crystal radio

Schematic