Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpfcso!hppad!derek
From: derek@hppad.HP.COM (Derek Schuurman)
Newsgroups: sci.electronics
Subject: Re: info on Crystal Radio kit or schematic
Message-ID: <2570001@hppad.HP.COM>
Date: 27 Oct 89 16:22:08 GMT
References: <758@ccssrv.UUCP>
Organization: HP Panacom Automation Div Waterloo, Ont.
Lines: 66


You can easily acquire the parts and "Homebrew" your own crystal receiver!
The schematic shown below should work fine! You should have no problem getting
the parts and putting together the circuit shown below :          

   _____
   \ | / ANTENNA
    \|/ 
     |
     |                 DIODE
     +---------+---------I>|----------------------+
     |         |                                  |
     ( COIL    |                                  |
     (       =====                                O EARPHONES 
     (         |  CAPACITOR                       O 
     (         |                                  |
     +---------+----------------------------------+
     |
  -------
    ---   GROUND
     -
       
  COMPONENT SPECIFICATIONS:
  ************************

  ANTENNA ->  The longest piece of copper wire you can string up (make sure
              it doesnt touch anything that could short it to ground ie. 
              eavestroughs, waterpipes etc.) 

  COIL ->  wind about 50 turns of insulated copper wire around an old toilet
           roll. (you may wish to shelac the toilet roll to make it more solid)

  CAPACITOR -> Pick this up from your friendly neighbourhood electronics store
               (Radio shack should have it as well).  The part you need is   
               a 0 to 365 pF variable capacitor.  These can be ripped out of
               the tuning sections of old radios as well.

  DIODE -> A "crytal" germaniun diode (some time called a "cat's whisker")
           A 1N34 should do the trick.  These can be obtained from almost any
           electronic store.

  EARPHONES -> What you need is some very high impedance headphones.  The old
               headphones that were used with AM portables (remember the
               little white earpieces that you stuck in your ear?) would be
               ideal.  Any piezo-electric type of headphone should do.

  GROUND -> Anything that is in some way connected to a good ground - a water
            pipe (Make Sure you dont use a gas pipe), or connect to the third
            prong ground on the outlets in your house (make sure there's no
            possible way of accidentally contacting the live a.c.!) or drive
            a long metal rod into your backyard and clamp a piece of copper
            wire onto it.



Dont expect the volume on this unit to be extremely loud - it's built entirely
out of passive components and is using the power from the radio wave itself 
to produce the sound. If you can't hear anything, check your connections and
get a longer/better antenna until it works!

    GOOD LUCK!   Let me know how it goes if you decide to build it!

Derek Schuurman  VE3OXK
derek@hppad.HP.COM