Magic-On-Stilts Radio

Tom's Designer EM83 Regenerative Radio

This effort is reminiscent of The Space Needle which was a shortwave radio constructed many years back. This fresh approach utilizes an EM83 Magic Eye tube with tunes the AM broadcast band. These tubes feature two green light beacons with one vacillating with signals as they are tuned and the other does so with modulation. They are not only beautiful to behold but are highly entertaining as well. I am told these tubes are extraordinarily rare and as such will be very valuable. I have searched the world over and have purchased all that I have found but have not found anymore in over a year.

The tube is mounted on 1/8” copper tubes 5” tall. They are secured in a base that passes the tips into the body of the set. All components are likewise sitting on stilts of 1/16” copper tubes with the larger positioned in the back at about 2 ½” tall and descending in height around to the center. These tubes also pass into the body of the cabinet where they are soldered in the circuit. The only items that is not on display are the 1n4004 diodes and the 22 ohm resistor because they become rather warm during operation. The tuning capacitor and the amp/speaker are also mounted inside the cabinet.

Power is provided by a P-T transformer purchased from Antique Electronics. It puts out about 150vac for the plate and 12.6vac for the filament. Both are converted to dc with the diodes and the 12.6 volts is reduced to about 6 with the 22 ohm resistor. All six wires coming from the transformer are conducted into the cabinet by way of a 3/8" glass tube. The variable capacitor is 390pF and is used with a 182µh honeycomb coil I wound using 175/46 litz wire to form the tank. A trimmer capacitor purchased from Jameco Electronics couples the antenna to the coil and is set at 39pF capacitance. A very nice miniature switch from Radio Shack handles the power off/on duties. I have purchased these style of switches from several other suppliers but they were extremely poor quality. The small amp and speaker provide all the volume one could want and is operated on about 12vdc. The solid brass knobs are made of stock I get from Enco Machine and all brass bolts, screws, nuts and washers come from McMaster-Carr and from Micro Fasteners. All brass is polished to a brilliant shine before being used on the set.

Highly flamed tiger strip maple was carefully steamed and bent to shape, thoroughly dried and then mounted on the frame work prepared just for this radio. After all fitting and cutting was complete the body was sanded to 320 grit, sealed, stained, shaded and finished with satin nitro cellulose lacquer. The cabinet is 2 ½” tall and 9 5/8 long.

Tom's Designer EM83 Regenerative Radio, front view
Tom's Designer EM83 Regenerative Radio, top down view
Tom's Designer EM83 Regenerative Radio, close up