Lem's Rook Coil Set
Lem's set uses air wound Rook coils: #16 enameled wire for the antenna and detector coils, and #18 enameled for the air wound trap. The set is in three sections, which allows adjustment of the coil spacing. A saw horse table was used as a base.
The phones elements are WW2 field telephone sound powered elements in a vintage headset frame.
Notice that each chassis consists of a combination
of plexiglass and poly-coated wood.
The traps are wound on FT82-61 toroid cores, with trimmer and
padder caps. The switches are from micorwave radio equipment.
Here is a closeup of the detector board. The home made vernier
uses parts salvaged from a TV tuner and VCR.
Rook Coil Form
Schematic of set.
Larger View
Back to the Birmingham Group Radios.