Tom Kipgen's Designer Radio
The Brass Tack Crystal Set
When Dave Schmarder told me of the Heart of England Crystal Radio Club it stirred a great deal of excitement in me. But when I viewed some of the work the members have done I was truly awed. Then Dave told me that in order to join this prestigious group I would have to construct a crystal radio worthy of their consideration. This was a most serious challenge for me considering the caliber of craftsmanship displayed on the Club’s website.
The Brass Tack Radio is the result. A crystal set that sports a choice of a diode for detection or a detector stand that is mounted on the top panel with either a chunk of pyrite or galena crystal. The stand itself weighs in at about 1/3 pound or 150 grams due to the thick brass bass and top along with a brass control shaft and housing. The control shaft action is managed by a brass ball bored to the diameter of the shaft and then split in half in order to conform to the shaft’s surface. These balls then are housed in the brass cap that can be tightened down or loosened up as needed.
The set represents a couple of firsts for me. Using solid silvered wire to complete the circuits was a completely new technique and perhaps the results reveal the lack of practice and skill. The other is the implementation of an actual tuning dial that is housed behind a convex glass lens. The frame for this lens was extraordinarily challenging in that a bevel holding the lens had to be machined so to hold the lens firmly against the panel while not binding or stressing the glass. A brass pointer was machined to fit the horizontal shaft shown which is activated by matching brass bevel gears. A vernier drive above the gears drives the vertical shaft to the 365pF main tuning variable capacitor mounted on an aluminum plate on the floor of the cabinet. Another 365pF provides antenna tuning for the circuit while a honeycomb coil I wound to 240 µH using unusual tattoo gun cloth covered wire completes the tank.
The cabinet is constructed of tiger maple as are the knob skirts under padauk wood grips. Everything was stained and shaded with colors I mix here and then finished with nitro lacquer I flatten in my shop. My sincere hope is that this effort will be favorably received by the Heart of England Crystal Radio Club and that I might be considered for membership there.