The Atwater Kent model 48 is a 6 valve T.R.F. (Tuned Radio Frequency) broadcast receiver made in the U.S.A. in about 1929. It was one of a series of radios in a long wooden box which was nicknamed a "coffin" due to its shape. The coffin style radio traditionally had knobs on the front, a flip up lid, and wires coming out the back. The same style box was used on the Atwater Kent model 20C and model 33. These radios were sold in the U.S.A. as well as Australia. This is a battery radio, so it requires external batteries or a power supply. The radio was ideal for homes that did not have electricity connected. A battery "eliminator" could be used instead of batteries, when the home became connected to electricity. The radio requires an external speaker. You could attach any type of speaker you wanted to. There was an Atwater Kent model "E" speaker which looked similar to a conventional speaker, or you could attach a "horn" type loudspeaker of the many brands that were available, or you could use headphones. I use a small English made Brown horn on this one.
The radio works very well. There is plenty of volume from the horn loudspeaker, and it is easy to tune in a station. I was surprised by the sharpness of the tuning. The two volume controls take a little getting used to, as I quite often get it either overloading or oscillating. It takes a little bit of adjusting. The set requires a good aerial. It looks very nice, with the horn sitting on top, and the eliminator out of sight on the floor.
This radio was in very good condition when acquired, with a lot of dust inside it and a small amount of rust on the metal part of the chassis. The front is a metal panel, painted with brown "wrinkel" paint and is in very good condition. The brown bakelite knobs were also good and had lots of dust on them (visible in the photograph). The front panel has a gold badge, and gold screws, which are a bit dull, but still good. The wooden box has a thick coating of lacquer with some minor cracks and marks and is so good it is hard to believe it is original.
The photograph shows the battery cable coiled up inside the box, and the number 12A output valve near it. The other valves have the green leaf transfer visible on their tops. The two nearest the 12A valve were faulty and have been replaced. The 2 round cans are the audio transformers and the tuning condensers are partially visible.
The radio consists of a wooden box with a flip up lid, and a metal front panel. By undoing the front screws, the radio can be withdrawn through the front. The metal front panel is attached to an "L" shaped metal chassis, which has bakelite valve holders on the back. The wiring is point to point using spaghetti covered tinned copper wire. The battery lead is a cable containing cotton covered individual wires. The valves are in a line across the radio with the 3 RF valves at the left, the detector, then 2 audio valves on the right. The audio output valve is a 12A but the circuit shows that an 01A or 71A will do just as well. All the other valves are 01A type valves. Five of the valves are Sylvanias with the Green Leaf transfer visible on their tops. The other one is an RCA valve. There are 3 tuned circuits in the plates of the RF valves and an RF choke in the grid of the first RF valve, connected to the aerial. The tuned coils are arranged each on a different axis to avoid coupling. The three single gang tuning condensers are coupled together with a metal band. This gives one knob station tuning, calibrated from 0 to 100. Older models had a knob for each condenser. There is a small knob below the main tuning knob that is used as a vernier tuning control. It has a rubber wheel which runs on the rim of the main tuning knob. The audio amplifiers are transformer coupled, and the speaker is directly in the plate circuit of the final audio valve, so it has HT running through it. The volume is controlled through 2 rheostats which vary the filament voltage. One is for the 3 RF valves, and the other is for the detector. There is a pull type ON/OFF switch that removes the filament voltage.
The battery cable had several wear spots which had exposed the wire. I took off some of the old style "black jack" insulation tape and used black heatshrink tubing to cover the bare spots. Two of the valves had open circuit filaments, possibly burnt out, or perhaps broken during the shipping to me. The grid leak detector was also open, so I hid a 2 meg resistor under it, and the set came to life. I will put the correct grid leak in when I find one.
The set requires an "A" supply of 5 volts DC for the filaments, a "B" supply of 125 volts, 67 volts and 22 volts DC, and a "C" supply of minus 10 volts DC. I use a Philips 3002 battery eliminator to supply the "B" and "C" supplies, and I had to build a small 5 volt supply for the filaments. It sits underneath the eliminator.
In 1895 Arthur Atwater Kent started the Kent Electrical Manufacturing Company in Philadelphia. He made motors and fans and in 1902, started manufacturing small electrical devices. They began to make automotive devices and then radios. Their radio cabinets were made by Red Lion, Kiel, and Pooley companies. At one point during the 1920's, his radio company was the world's leader. He spent $500,000 on advertising in 1924. By 1927, he was spending many millions on printed advertising and his radio show, The Atwater Kent Hour, was the most popular show on radio. The depression affected the sales of radios. Atwater Kent tried a number of cost-cutting measures to keep his company afloat. However in 1936, he closed his factory doors and retired to Hollywood. The Atwater Kent factory which was located at 4745 Wissahickon Avenue in North Philadelphia can still be seen with the name engraved above the door.