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Message-ID: <EA42441F7E7344A7B113CE61A4DC5F1E@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <00b701c97028$b2fd5780$0301a8c0@mal769a60aa920>
In-Reply-To: <00b701c97028$b2fd5780$0301a8c0@mal769a60aa920>
Date: Tue, 6 Jan 2009 19:27:24 -0000
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Subject: LF: Re: Razor blade RX
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Dear Mal, LF Group,

Searching on Google under "razor blade radio" or "foxhole radio" will give 
you a few thousand detailed descriptions...

The use of similar kinds of metal-on-metal contact as a radio detector was 
known a long time before WWII - For example, J.C. Bose, who did much early 
microwave work in the 1890s, used this kind of detector (see 
http://www.tuc.nrao.edu/~demerson/bose/bose.html ).

I used to play around with this kind of thing when I was a kid - the problem 
was getting hold of the right kind of razor blade. The ones I could get had 
some sort of insulating coating on them and didn't seem to work. Apparently, 
WWII era razor blades didn't have that. I did get it to work with various 
other odd bits of more or less oxidised metal - I found the trick was to get 
the "cat's whisker" to  touch very gently against the metal surface, but of 
course this was horribly fiddly. I rapidly came to the conclusion that 
diodes were easier to come by and worked a lot better - I suspect the same 
will be true even after WWIII... and you still need to find the headphones!

Cheers, Jim Moritz
73 de M0BMU


----- Original Message ----- 
From: "mal hamilton" <g3kevmal@talktalk.net>
To: "rsgb" <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, January 06, 2009 6:00 PM
Subject: LF: Razor blade RX


Since I mentioned a Razor blade and fence wire RX a while back I have had 
several requests for a circuit. To give others the opportunity to submit a 
cct I will await replies. This method was used successfully  at Coldiz and 
other POW camps to receive BBC broadcasts.
Let us know how you would approach the subject. This is applicable to MF/LF 
since the broadcasts at the time were receicved on these bands.
Build one and have a QSO using this RX
g3kev