EQUIPMENT UPGRADING

THE ALR-35

Improvements to the ALR-34 capability began in 1968 with the installation of the ALR-35 in some EC-47s. This system coupled the basic ALR-34 with the Nortonics 1060 airborne data processor. It was designed to improve both quality and quantity of fixes and to provide for more rapid acquiaition of fix positions. The interface of the systems did not change the frequency spectrum, bearing accuracy or input from the antennas, since the ALR-45 continued to be heart of the ARDF portion. The output from the Franklin Data Printer, however, was considerably different, since the automated portion performed many functions previously done manually by the navigator.

The 1060 processor compensated for induced airframe errors, converted the target magnetic bearings to true bearings, calculated the target location relative to the doppler set point, and determined the circular error of the fix. It provided instantaneous readout of relative bearing to the target after on LOP was taken, continually updated range and bearing to target after two LOPs intersected, and computed the radius of the fix after three LOPs were taken. In addition, it simultaneously displayed relative bearing and range with each succeeding LOP. The zealous reader may obtain full technical data from the documents listed in the footnotes, but it was obvious that the ALR-35 gave the navigator additional time to position the aircraft more accurately for optimum data information. Figure 4 shows the ALR-35 control panel and keyboard (they were actually side by side on the console) by which the navigator controlled the equipment.

As of the summer of 1970, 14 ALR-35s had been installed in EC-47N/P/Q TEWS aircraft, but concurrently, a new system was being "married" to ALR-35 which would greatly increase its capabilities.

THE ALR-35/38

On 12 and 13 March 1968, representatives from Hq USAF, Hq TAC, Hq AFSC, Hq USAFSS, WRAMA, and Sanders Associates, the ALR-35 developers and contractor, met to discuss the addition of a VHF ARDF capability, but, as the meeting progressed, it became apparent that the equipment had an inherent capability to operate over a much wider frequency range than previously envisioned. Preliminary information indicated that this expanded VHF ARDF capability (16 to 150 mhz) could be acquired at little additional cost and with only a very slight delay in delivery.

Subsequent to the meeting it was determined that the modified ALR-35 could be made responsive to Steel Tiger VHF ARDF requirements if the upper frequency limit of the modification were 180 mhz rather than the 150 mhz discussed earlier. From these discussions came the ALR-35/38.

The first intimation of the propossed deployment came in September 1968 when CINCPACAF and Seventh Air Force were notified that the Air Staff was establishing an interim "Mini-Mod" system. This action was taken to provide and immediate VHF DF capability in the two to 50 mhz spectrum, pending development of the full, or "Maxi-38" system. The message notifying Seventh Air Force of the proposed action said in part: