This is a Collins Radio Permeability Tuned Oscillator Unit, used in the military RT-311/ARC-38; it tunes from 200 to 300KHz over 12.5 turns of the shaft. The engineering, construction, and calibration of this type of oscillator represents some of the finest radio design of all time.

You can read a fantastic article about these devices here: http://www.radiomuseum.org/forum/design ... s_pto.html

The sealed cylindrical unit (shown disassembled in the first picture) includes a permeability tuned inductor, along with a nifty key/lock type mechanism with finely adjusted mechanical offsets along the length of travel of the core to correct for minor nonlinearities in the oscillator's frequency scale. In other words, this thing was designed so that the dial calibration of the unit it was in was basically PERFECT.

The shell/base has two peanut tubes in it for the oscillator and buffer; they are both type 5902.

The unit has not been tested. If you enjoy studying magnificent radio design and engineering, add this to your collection, and pass it along to someone else who will enjoy what it is in the future.

Price $25 plus shipping. Size 8" high x 2-1/2" x 2-1/2". Weight 1 lb 5 oz (i.e., not expensive to ship).

Internal picture:


Shell/base:


Complete unit:

Item sold.