Green Ears Radio

Tom's Designer EM83 Tube Radio, at

Several improvements were incorporated into this radio the most obvious being a technique used in guitar construction to make the figure in fiddle back or quilted maple “pop’ or stand out more than usual. This set is made of fiddle back and the markings are outstanding under the orange stain. The other improvement is in the dial mechanism which features a polished steel shaft rotating in a solid brass collar drilled and honed to size. This promotes very smooth and accurate tuning of the radio across the entire band.

The maple sides and top were steamed and carefully bent to shape and was then attached to the frame work that was constructed just for it. The front panel is a matching piece of the same material and both were sanded down to 320 grit sandpaper and then a rich orange alcohol stain was applied and dried thoroughly. It was again sanded with 320 grit and this process was repeated twice. Then everything was sealed, shaded and finished with multiple coats of satin nitro cellulose lacquer. A speaker grill was constructed form more fiddle back on a metal lathe and vertical mill with precisely spaced holes and then black fabric was glued to the back before being attached to the set. A bezel was also fabricated on these same machines for an exquisite deeply concaved crystal. These two parts required more time and labor that the rest of the radio but are well worth the investment.

I used my standard schematic for an EM83 tube and added a small amplifier and speaker. These tubes are extremely difficult to find with the last one I bought being in early 2012. But they are so very unique with the green beacon on the left vacillating with tuning signals and the one on the right doing so with modulation. It is powered by 160vdc out of a transformer that also supplies the filament and amplifier voltages. The transformer puts out ac current so 1n4004 diodes were used to convert that to dc. A variable trimmer capacitor set to 40uH couples the antenna to the variable tuning capacitor and the coil. The tuning capacitor metered 410pF so the torroidal coil was wound to 180uH to complete the tank.

The radio tunes the AM broadcast band and functions extremely well using my 60’ antenna that is 10’ off the ground.

Tom's Designer EM83 Tube Radio, side
Tom's Designer EM83 Tube Radio, other side
Tom's Designer EM83 Tube Radio, speaker grille detail