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Band Switching One Tube Radio

 

Below are 3 scans.  The 2nd is the construction of a coil that will allow band switching instead of plug-in coils.  A suggested circuit is shown in the 3rd scan.

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On the 3 inch long form pictured above the sections are from left to right:  L1= 10 turns of #26 DSC wire; L4= 3 turns of #26 DSC wire; L3 = 7 turns of #26 DSC wire; L3 = 24 turns of #25 DSC wire and last L5 =1 turn of #26 DSC wire wound in the opposite direction.  Coils Li thru L4 are wound in one direction, L5's one turn is wound in the opposite direction.

The loops on the top of the coil form are the for the connections to the circuit.  From right to left:  Connect first loop to the junction of the 100 mmf cap and the 3 meg grid leak resistor;  Connect the 2nd loop to Switch tap 1; Connect Loop 3 to Switch Tap 2;   Connect Loop 3 to Switch tap 3.

The three connections shown on the bottom of the coil are from right to left:  Connect to 2.5 mH choke; Connect to the plate of the tube;  and the last connection on the far left is to the cathode of the tube.