Chapter 3

USAF ARDF Equipment: Operation

The 460th Tactical Reconnaissance Wing Manual 55-1, March 1968, has a full description of ARDF operational procedures. For the purpose of this study, it should be pointed out that two problems are involved in locating an enemy transmitter. The position of the aircraft must be known precisely, and at least two relative bearings taken on the transmitter, as shown in Fig. 6.

Once the AN/ALR-34 has "locked on" to a target, its relative bearing, the Doppler data on the position of the aircraft, and the C-12 CDompass heading are integrated and displayed on demand by the navigator on a paper tape. This process can take place less than one second after a lock-on to a target. The navigator must then make several computations before plotting a line of position (LOP). This entire procedure is repeated for a least one more bearing and, ideally, several widely spread bearings, to get the best fix. While a target can be fixed on a single aircraft heading, the navigator usually directs a heading change either to secure better bearings on the target or to stay close to it.

A proficient navigator can compute his data, plot between six and twelve LOP's, fix a target, and pass his information for KY-8 transmittion to a Direct Support Unit in seven minutes. He uses a 1:250,000 scale chart and is capable of measuring within 1/10 degree and 1/10 mile. His judgement must come into play in deciding which lines of position for his fix. Considerations such as terrain, weather, and a unreliable Doppler affect individual bearings. Also, the present state of his equipment makde less than a 250-meter radius fix unlikely. Indeed, up to a 10,000-meter radius fix is reportable. The fix radius is measured from the center of the fix (determined by bysecting the exterior angles) to the farthest intersection. The radius tells an evaluator that the enemy transmitter lies within a circle whos radius is the fix radius.

As indicated, the navigator passes his fix data to the special equipment operator at the "Y" console, who immediately transmits it on the KY-8 to the closest Direct Support Unit. The fix information also becomes part of a log, which the equipment operator forwards through his SS unit to the 509th RRG.