AN/URT-12 Transmitter

former Coast Guard unit

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This set was made in 1955. I bought serial #40 at Groban Supply in Chicago. It's dirty on the outside from sitting in the warehouse for many years, but nice and clean inside. I just got it out of the truck, have not had time to clean it yet when the pictures were taken. Looks like it could be fired right up! This unit may also be known as the T-408/URT-12. Information on the internet indicates the URT-12 covers 2-30 MC, 75W carrier, AM and CW. The (option) transmitter control unit is the CANU-23423 made by (Seaboard Electric) and the PP-950/URT-12 is the 115VAC power supply. One observation is that the large-ish modulation transformer is rated 14KCT to 12K, 90 watts RMS. The modulators are 4-65's as are the final amplifiers. The unit also has built-in antenna coupling. It took 2 years of searching to find the manual.

SCHEMATIC 4.7MB PDF file
Preliminary Manual 253MB PDF file including above schematic

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Front view
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Power supply unit
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Metering panel
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RF tuning controls
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Top of unit with classic insulator. This would connect to a long wire antenna.
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Nomenclature tags
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Power supply drawer.
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Top of RF deck. Variable inductor is part of antenna tuning system. PS tuning is at the top of the picture (left side of the unit).
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antenna tuning components directly under final RF deck
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Modulator section (under antenna tuning section). The large transformer to the right (rear of unit) is the modulation transformer.
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IPA (driver) section uses an 807. To the right in the picture (rear of unit) is the crystal oscillator assembly.
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Power components in RF section. Control relays are to the right (front of unit).
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Crystal (channel) selector
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tubes near the crystals, perhaps the oscillator and buffer.
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IPA (driver) tube circuits.
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control relays
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side view of final RF deck
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RR deck showing blower and PA tubes.
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Part of the antenna tuning unit. There is a much larger switch behind the small wafer.
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Another view of the tuning unit. In the very back can be seen what looks like a 6CD6 or 6BG6 tube.