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 Post subject: Razor blade detector for a foxhole radio
PostPosted: Sep Wed 15, 2021 5:43 pm 
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Joined: Apr Sat 25, 2015 2:58 am
Posts: 90
Location: Bangalore
Here's my version of a detector for a foxhole radio, using a spare carbon brush of a mixer/grinder instead of a pencil.

Image

Image

Adjustable carbon brush pressure and the moveable blade make location of a 'hot spot' quite easy.

Nandu.

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 Post subject: Re: Razor blade detector for a foxhole radio
PostPosted: Sep Wed 15, 2021 6:26 pm 
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Joined: Aug Thu 20, 2015 3:09 pm
Posts: 1624
Location: Albion, CA, USA, 95410
Very cool! Do you have any sort of a point or beveled edge on the brush?


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 Post subject: Re: Razor blade detector for a foxhole radio
PostPosted: Sep Wed 15, 2021 6:49 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: S. Dartmouth MA 02748-1225 USA
+1
A "modern" pencil lead is a blend of polymers that do not conduct very well. Artists very soft drawing pencil leads have a large percentage of carbon and may work better.

The razor blades of WW-II were treated with selenium and appeared blue, the selenium aids in the rectification. GL

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 Post subject: Re: Razor blade detector for a foxhole radio
PostPosted: Sep Wed 15, 2021 7:13 pm 
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madlabs wrote:
Very cool! Do you have any sort of a point or beveled edge on the brush?

Thanks!

No, the contact surface is quite flat. Maybe there's some uneveness that is not noticeable.

Nandu.

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Last edited by vu2nan on Sep Wed 15, 2021 7:25 pm, edited 1 time in total.

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 Post subject: Re: Razor blade detector for a foxhole radio
PostPosted: Sep Wed 15, 2021 7:24 pm 
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Joined: Apr Sat 25, 2015 2:58 am
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Location: Bangalore
Chas wrote:
+1
A "modern" pencil lead is a blend of polymers that do not conduct very well. Artists very soft drawing pencil leads have a large percentage of carbon and may work better.

The razor blades of WW-II were treated with selenium and appeared blue, the selenium aids in the rectification. GL

Hi OM Chas,

You're right, the carbon brush beats pencil lead.

The razor blade shown is still available. It's not blue but works quite well.

73,

Nandu.

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