The UNITO 5 is a five valve TRF (Tuned Radio Frequency) receiver covering the broadcast band. It was made by The United Factories Co, 1276 West 3rd Street, Cleveland Ohio, in approximately 1925, and is serial number 2995. It is made 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. 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.
It uses five UX201A valves. These are a balloon shaped glass triodes made by RCA. The first 2 valves function as RF amplifiers, the next is a grid leak detector, and the last are audio amplifiers. The radio is very simple and has few components. The two tuned stages use independent tuning condensers and coils. The coils are a large diameter, and wound with green cotton covered wire. They are unshielded and so are arranged at right angles and separated to prevent coupling and feedback problems. The wiring uses uninsulated tinned square bus bar wire, and some leads are covered by woven spaghetti.
CONDITION
The radio is in very good condition and even has the original label on one of the coils. It was bought from Perth in Western Australia but was damaged in transit. The two audio transformers broke loose and had their connecting wires broken off. I was able to reconnect them on one transformer but the other one had them ripped from inside the windings. This transformer was rewound. The valves, case, and all else survived the journey.
The radio was reassembled and worked first time. A few minor repairs were needed to improve performance. A loud crackle when the front panel was moved, was traced to loose connections on the grid leak capacitor and resistor. Another intermittent, causing low volume was traced to a dry joint, so all joints were inspected, some resoldered, and all nuts and screws tightened. The front is a bakelite panel, engraved with the name and control labels, and is in good condition. The brown bakelite knobs were also good and had lots of dust on them. 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 chassis is wood and all components are screwed to it. There is wiring underneath as well as on top. The battery cable exits through a hole in the bottom, and the aerial wire comes in through a hole in the back. By undoing two screws on the front wooden bar, and two screws on the chassis, the front panel and chassis can be lifted up, and out of the box.
CONTROLS
There are 3 large knobs for tuning the stations, each calibrated in divisions labelled 0 to 100, as this was radio was built before dials were marked with station names. There are two small knobs for the volume, which are both wire wound rheostats, the right one to adjust the filament voltage for the RF valves, and the left one to adjust the RF bias on the RF valves. There is also a pull type ON/OFF switch, which is in the common battery lead, and so turns off the high tension and the filament supply. There is a jack on the left hand side for plugging in headphones or a speaker. The jack is in the anode circuit of the audio output valve and so has high tension on both contacts.
PERFORMANCE
The radio works very well. There is plenty of volume for a horn loudspeaker or headphones, and it is easy to tune in a station, but requires a large aerial. The tuning of the 3 dials is not difficult. The right most dial, labelled 3, is the sharpest and most effective tuner, so this can be used to select the station required. The middle dial, labelled 2, is used to peak the signal, and the left most dial, labelled 1, is used to tune the aerial, and this is very broad. I was surprised by the sharpness of the tuning on dial 3 and the good separation of the stations, with only a couple overlapping. The two volume controls are easy to use, and I can make the radio oscillate if I have them both on full for a strong station. The right control can be rotated fully counter clockwise, until the RF valve filaments are off, and the radio still performs well on strong stations.
The photograph shows the 2 audio valves at the left hand side back and centre, near the 2 audio transformers. The detector valve is at the back right hand side, near the gridleak. The two valves near the front are the RF amplifiers. There are 3 tuned circuits in the grid and anode circuits of the RF valves. The aerial coil is a single winding with an aerial tap and tuned by the left hand dial. The other 2 coils have a primary winding for the anode circuit and a tuned secondary winding for the following grid circuit. The three single gang tuning condensers have individual knobs. The audio amplifiers are transformer coupled.
The set requires an "A" supply of 5 volts DC for the filaments, and a "B" supply of 90 volts and 45 volts DC. I use a Philips 3002 battery eliminator to supply the "B" supplies, and I had to build a small 5 volt supply for the filaments. It sits underneath the eliminator.
Copyright
Ray Robinson vk2no