[Boatanchors] Crystal Set Progress

Al Klase ark at ar88.net
Fri Apr 24 00:36:46 EDT 2015


Gene,

I see two problems with that approach. Perhaps the biggest is that if 
the slider touches two adjacent turns, it results in a shorted turn in 
the coil that causes a great amount of loss.

Even if you can avoid that problem with a carefully designed slider, 
it's still difficult to design a high-performance receiver around a 
simple untapped inductor.

The difference between a brain-dead design and a good one is quite 
striking. You can get a feel for some of the issues and appropriate 
circuit topologies here: 
http://www.skywaves.ar88.net/xtalset102/xtalset102.htm

Sorry, you got me on one of my favorite subjects.

Al

Al Klase – N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

On 4/23/2015 9:52 PM, Gene wrote:
> Why not use a variable inductor instead of tapping?
>
> The one I built in the late 40's had a coil wound with magnet wire on 
> an oatmeal box and a 'slider' cut from a tin can that ran on an arc 
> over the length of the coil.
>
> It had a real cat whisker & xtal and a pair of cans (earphones to the 
> newbees)
>
> Gene, WØQFC
>
>
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