CRYSTAL RADIOS
 I work on vintage radios as a counterpoint to my professional career as a Field Applications Engineer for a major semiconductor company, as in a billion transistors under your thumb nail.  It's refreshing to work on devices where you can actually see the individual components.  In between high-end ommunication-receiver restorations, I build crystal sets.


A Crystal-Set Circuit Tutorial:


Crystal Radio Coil

Coils can make or break a crystal set.  Here are some thoughts on their design:
     

One of the weak links in many sets is the earphones.

Headsets


Deck Talker


Sound-Powered Telephone Spotter's Guide


The Search for Steel Galena

Steel Galena


You can mount your own mineral crystals for use as detectors:
      
Mounting Crystals


A look at some vintage detectors:

 TWO WIRELESS DETECTORS

Perikon Detector


Crystal-Set Projects:
Pretty Good Crystal Set Build a

Pretty Good Crystal Set

The PGXS Mark II
People building their own PGXS's

at the Radio Technology Museum
Crystalset front end / antenna tuner
Make Your PGXS Double-tuned

Build a second coil-capacator assembly on a separate base.  Connect it to your antenna and ground, and place it beside your PGXS.

Tune the original  set to minimum capacity, and bring the two coils together, end to end, as close as possible.

Search for stations using the coil taps and capacitor on the "primary," The front end.

Then pull the coils apart, and retune the secondary.  You'll be amazed.  Crystalsets don't get a whole lot better than this.
A minature crystal set for urban areas:  
City Mouse Crystal Set
Crystal Radio SkyWaves High-Performance Crystal Set
A simple but effective
 SINGLE-TUNED SET
that rejects short-wave signals.   
Crystal Detector
Now you'll need a detector stand.  Here's one you can build: 
An experimental
 SHORT-WAVE CRYSTAL SET
Short-wave Crystal Set
WWI German Field Receiver
WWI German Crystal Set - Telefunken? WWI German xtal set in the Signal Corps Museum.  This radio is associated with Edwin Armstrong, who's unit in France, 1918, did evaluations of captured equipment..  Signal Corps blueprints available here:

http://users.erols.com/oldradio/eha13.htm

Telefunken Detector

Detector Closeup


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