[Boatanchors] Crystal Set Progress

[hwhall at compuserve.com]

>
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.
>

Some of the high-end old-time crystal sets had dual sliders on the tuned coil, presumably to let one vary the detector tap-off as well as the number of turns across the tuning capacitor.

Wayne
WB4OGM


-----Original Message-----
From: Al Klase <ark at ar88.net>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Thu, Apr 23, 2015 10:36 pm
Subject: Re: [Boatanchors] Crystal Set Progress


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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