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Radar equipment with 2x 8012 triodes.

This is the RF section of the AN/APQ-9 (the "Carpet III" jammer) radar countermeasures transmitter. It uses two 8012's as a push pull oscillator, with tuning achieved by varying the width of the plates between them. It operated between 475 and 585MHz and was used to jam the German Wurzburg gun laying radars by radiating wideband noise. The 8012's were modulated by a pair of 807's that in turn were driven with a wideband noise signal generated by a 931A photomultiplier excited by a filament lamp.

The front panel has several controls that act mechanically on the RF circuitry; see pictures below for futher descriptions of these. The rectangular hole top right probably had some form of mechanical counter as a there is a gear wheel just behind connected to the Tuning control. The Lock lever acts on this, preventing the Tuning control from being moved. The Xtal contains a 1N22 crystal detector. Front panel


Side view
In the above picture the cylindrical units to the lower left and right have sliders which are adjusted by the Tuning control. At the bottom left can be seen the crystal detector housing above the Antenna connector.

Side view
In the above picture, the Antenna Matching control adjusts a slider in the square section. The gear-wheeled control is the Tuning control. The control that can be seen above the transformer is used to move one of the 8012 valves closer or further away from the centre of the RF circuitry, see below. Some components are missing but it appears that the coaxial cable that connects to the Antenna socket on the front panel connects to the square section at the left as in the above picture.

8012 RF  circuitry

Closeup of the 8012's, one fitted and one removed. The Antenna Coupler control causes the rod running across the middle of the picture to move the coupling loop, centre, in and out. Adjusters inside the unit move the valves towards or away from the central RF circuit. The Tuning control moves the flat fingered metal components in the centre of the picture apart.


Thanks to Richard Wurtzinger and John (G6RAV) for identifying this equipment.

This file was last modified 11:54:15, Sunday July 24, 2016