Crystal Radio
stay tuned crystal radio and tube radio website
crystal set



baldyodyne crystal radio

TK-3
(as Steve calls it)

Designer Steve Bringhurst
Builder Darryl Boyd


Note:

This is not intended as a "How To" article for a beginner. The following is supplied as information only. Some of the techniques used in the construction of this radio are very advanced and not recommended for a beginner or even an intermediate builder.
 




  Baldyodyne 3 Parts List


 
C1 (A & B)     Air Variable, duel gang, 15-500 pF each side, ceramic insulation

C2                   Air Variable, single gang 15-497 pF, TRW, silver plated, 
                        ceramic insulation

C3                   Air Variable, single gang 15-497 pF, TRW, silver plated, 
                        ceramic insulation

C4                   Air Variable, trimmer. 59 - 131pf, ceramic insulation

C5                   .1uf capacitor

C6                   .47uf capacitor

S1 (A& B)      Rotary Switch, 2 pole 2 position, silver plated, ceramic insulation

S2                   Rotary Switch, 1 pole 6 position, silver plated, ceramic insulation

S3                   Rotary Switch, 1 pole 12 position, silver plated, ceramic insulation

S4                   Rotary Switch, 1 pole 12 position, silver plated, ceramic insulation

L1                 Tuner Coil, 660/46 Litz wire, air coil, 

L2                  Tuner Coil, 660/46 Litz wire, air coil,

L3                  Trap Coil, Amidon FT-82-61 Ferrite Toroid Core, #24 magnet wire, 
                       bifilar wound, 50-odd spaced turns, more or less, depending on the V/C
                       being used, 10 turns wound from one end of the other coil windings.

L4                  Coupling Coil, Amidon FT-82-61 Ferrite Toroid Core, 16 turns of 
                       #24 magnet  wire on each side, tapped every turn starting from one 
                       side for a total of 10 taps.

L5                  Detector Coil, Amidon FT-82-61 Ferrite Toroid Core, 50-odd spaced
                       turns, more or less, depending on the V/C being used

D1

R1                 250k ohm pot

H1                 RCA "Big Cans" from Decktalker unit

T1                  UTC A27 transformer 
 


 
 

Circuit Details


Coupling Coil  (L4)

This is a tough coil to build. Creating the taps is the hardest part.
I used special magnet wire that the insulation "burns off" as you solder it.
Actually, it works as a flux while coming off with your soldering iron.

Wrap the coil first. 16 turns Of #24 ga. wire on each side.
Tin the knee of each wire that is to have a wire connected to it.
Solder on each wire to the knee of the toroid coil wires.
Sounds simple....but it is not!

Finished coil with header epoxyed on each side to give it strength.

Each joint was inspected with a jewelers loop to make sure it did not short out
with the joint next to it. 

I then applied a thin coat of styrene mixture between the joints only to further isolate the joints. 

This styrene mixture was picked because it will not lower coil Q as much as most things. Anything will lower the Q of a coil, some more than others. The mixture is made with Acetone (or MEK) and styrene peanuts. The styrene peanuts are the kind you pack things in to mail items, you know, the ones that go everywhere when you open up a package!! LOL   Only use enough on the coil to do the job and be very careful. This mixture is very flammable and not good if inhaled. Use plenty of ventilation. 


 
 
Trap Coil (L3)

First wrap (gold) is 50 turns of #24 ga. wire non-solderable enamel magnet wire. 
The toroid coil came out to 165 uH.

With the Cap I'm using, that should get me a range of .530 to 1.76 MHz.
 
 

Second wrap (red) is 10 turns of  #24 ga. solderable enamel magnet wire.
Tapped every other turn. Simular to coupling coil (L4) above.

 


 
Detector Coil (L5)

The detector coil is almost the same as the trap coil (L3) except
it doesn't have the second winding on it.

Wrap  52 turns of #24 ga. magnet wire. 
The toroid coil came out to 170 uH.

With the Cap I'm using, that should get me a range of .530 to 1.72 MHz.?

 


 
 
 
Tuner Coil  (L1)


660/46 Litz wire, basket weave.

 


Radio will be broken down into three sections
 


Section A


Section B


Section C
 


Photos Of The "Prototype" Radio
Under Construction---Not Wired Up Yet.
 


 
 

Reworked Proto Type
ABS and Teflon were incorporated to isolate all metal parts from the wood
Where it counted.
 


 


 
 


Tuner Section



 


Trap Section



Coupler / Detector / Matching
Section



Special Thanks to

Steve Bringhurst
For sharing this radio with us





Crystal Radio
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© 1999-2010  Darryl Boyd,  All rights reserved
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I do not furnish them for  your gain from my hard work.





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