[Boatanchors] Crystal Set - Progress

[Richard Knoppow]

       The easiest way to get the coil is to wind it.  Its easy enough 
to make taps by lifting a little wire where you want the taps and giving 
them a twist before continuing to wind.  However, you don't really need 
a tapped inductor for broadcast reception.  I suggest making a simple 
loose coupler.  That is a relatively large fixed coil with a smaller 
coupling coil that can slide over it. The small coil is used to couple 
the antenna.  you need a large coil of sufficient inductance to resonate 
with the variable condenser you have.  A simple crystal set does not 
need more but, of course you can copy the arrangements used in the early 
days to increase selectivity by using a couple of tuned circuits.
        You can obtain high impedance headphones at reasonable prices 
from Playthings of the Past.   He is trying to retire so I don't know 
how much stock he has.  The highest impedance phones were the Trimm 
Featherweight Special (24 K)  and the Western Electric 509W, also about 
20 to 25K ohm.  Note that the old magnetic phones are quite resonant, 
not at all hi-fi.  Ususally the DC resistance is given as a spec but 
there is no fixed ratio of resistance to impedance.  Typically its about 
four to seven times but some magnetic phones have impedance that is only 
about twice the DC resistance.  Make sure you know what you are getting; 
magnetic phones were made in all ranges of impedance; at one time "Trimm 
made Featherweight phones with impedances as low as 10 ohms and there 
are lots of phones with relatively low impedance.
       You can feed the input of a high fidelity amplifier from a 
crystal set through a fairly high value resistor. Since they are not 
very selective the output is quite hi-fi.  Most AM stations these days 
use an enormous amount of processing but a few still broadcast decently 
high quality signals, the crystal set on a good amp will tell you 
exactly what is there.

On 4/23/2015 2:01 PM, rbethman wrote:
> I am still acquiring parts and pieces.
>
> I have one air variable that will go between the antenna and the 
> Galena detector.
>
> I am looking for the coil with taps and two air variables for the 
> bands to be selected.
>
> Then a high impedance earphone.
>
> I'll procure these remaining pieces from one of the "kit" outfits if I 
> need to.
>
> It has been hectic here with taking the sat dish off the roof, having 
> the roofing done, then moving furniture all over the place so the XYL 
> could have the carpet cleaned.
>
> It is always one thing or another.
>
> Regards, Bob - N0DGN
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
> Message delivered to 1oldlens1 at ix.netcom.com
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL