WK-20-8350 Telemetering Theodolite

The Warren-Knight WK-20-8350 theodolite is an integral part of the precision measuring system used by the FAA for calibration of navigation aids such as the Instrument Landing Systems (ILS), MLS, VOR, TACAN, and VORTAC. In ILS calibration, an operator tracks the “Flight Check” aircraft and adjusts the theodolite so that the image remains in the crosshairs.

The theodolite elevation readings are continually transmitted to the aircraft receiver by the UHF telemetric unit. The received theodolite signal is processed along with the received glide slope signal in the aircraft, to determine any errors in the signal of the ILS on-course. This process is repeated using the azimuth for the localizer. The information is used to adjust the angle of the ILS glide scope and localizer signal transmission.

The WK-20-8300 Series Theodolites have a bent axis type, a 21 power main telescope with a minimum focus of 100’. They also have a 4 power wide angle finder telescope viewed through the one eyepiece. The main telescope has a 42mm diameter achromatic doublet objective and an effective apperature of 40mm — resolving 4 seconds with a 2 degree field of view. The finder telescope has a 17mm diameter achromatic doublet objective and an effective apperature of 15mm with a field of view of 100 degrees. Sight through two pair: one fixed, one folding (hinged).

Comes furnished complete in a substantial carrying case and with the following accessories: a waterproof hood, a sunshade, adjusting pins, a spanner wrench, an accessory tool, a screwdriver, spare bulbs and a handbook instruction manual.


  • Length: 13.1”, counterbalanced, moisture and dustproof-internal focusing by rack and pinion – minimum focus 100’ with 21x power – all lenses with low reflection coating.
  • Main Telescope: 42mm diameter achromatic doublet objective – effective aperture 40mm- resolving 4 seconds – 2 degree field of view.
  • Finder telescope: 17mm diameter achromatic doublet objective – effective aperture 15mm – field of view 100 degrees.
  • Eyepiece: four element achromatic – .074” diameter exit pupil – 15/32” eye relief – molded soft rubber eye guard.
  • Sights: two pair, one fixed, one folding (hinged), mounted on telescope for quick alignment and spotting.


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