[Boatanchors] Crystal Set - Progress
Richard Knoppow
1oldlens1 at ix.netcom.com
Mon Apr 13 17:52:39 EDT 2015
One of my earliest projects was helping my dad build a crystal
set. He had taken a course in basic radio and it was a homework
assignment. We used a fixed germanium diode as the detector and wound
the coil on a toilet paper roll. The other stuff all came from some
local supply/surplus house including the military surplus headphones
(made by Utah I think). It was assembled on a breadboard (maybe an
actual breadboard) . The antenna was a wire running from a second floor
porch to the garage roof. It worked like a charm. I used to listen to
the Lone Ranger on it. Quite a bit later I built another on my own this
one using a galena crystal and cat's whisker. The detector worked OK
but was a pain to get working since one had to probe for an active spot
for a while and a spot that was good now might not be in a couple of
hours. These things are actually quite high fidelity if you feed the
output into a good amplifier. The headphones should be the highest
impedance you can obtain. No one makes such phones any more. The best
for sensitivity are probably Trimm Featherweight Specials with 24K
impedance. Brush crystal phones are even better but the chances of
finding a pair that work are very slim.
Its possible to improve the selectivity by proving for double
tuning and adjustable coupling from the antenna link to the main coil.
All of this was done a million years ago when crystal sets were used
for receiving telegraph signals commercially. The signals were
modulated, that is damped wave from spark or rotary arc.
If the kid isn't interested assemble one yourself and keep it
around to show off to visitors. If you get really ambitious you can
build a loose coupler.
On 4/13/2015 2:36 PM, rbethman wrote:
> All,
>
> I've got the Galena Detector package nailed in place. (One heck of a
> price too!)
>
> I'll make a cardboard tube of adequate diameter.
>
> I have more than enough #26 enamel wire on hand.
>
> I haven't located a couple of 365pf air variables yet. I did locate a
> 920pf, BUT it is all one piece.
>
> These are at least not crazy priced after comparing to the Galena
> Crystal Kit!
>
> Yes, I *DO* realize prices have changed over my almost 65 years of
> life! It is just hard to reconcile the numbers when I'm looking at a
> 11 year old that may or may not use it much. I have spoken with her
> Step-Father, and he is going to talk to her mother. I want to find
> out *IF* she would really be interested.
>
> If it comes down to it, I'll order the remaining parts that I can't
> scrounge.
>
> Seems I've trimmed a whole bunch of junque. To think that last year
> or so I even had an old SX-99 here that had a burnt transformer. When
> things container 60/40 solder, they *must* be collected, and a run
> about every other month or so they have a "Hazardous Waste Disposal Day".
>
> I've made at least four runs over the last two years.
>
> Now I'm trying to scrape the barrel for bits and pieces.
>
> Someone responded regarding the 8" SCT Telescope. No, she has NOT had
> it out. I'll fix that when I'm down there.
>
> She has one surprise coming that she has absolutely NO idea about!
> One each USB 200X portable Digital Pen Microscope w/Tripod and
> software going down with me. The Step-Father asked me why? I simply
> said that she can take a leaf, hold the backside to the microscope and
> actually see individual cells.
>
> He forgets that he and I didn't get this in school until 9th grade
> Biology!
>
> She is definitely into Earth and Environment!
>
> Regards, Bob - N0DGN
> <http://rover.ebay.com/rover/0/e11923.m43.l3160/7?euid=83af49f0273548088a7bf9ff446074aa&loc=http%3A%2F%2Fcgi.ebay.com%2Fws%2FeBayISAPI.dll%3FViewItem%26item%3D391029702438%26ssPageName%3DADME%3AX%3ARRNTB%3AUS%3A3160>
--
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL
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