With Gr Instruments

not only measurable but extremely accurate. The generators in use in their

Figtjhe 1. In the screen room of American Airlines radio-overhaul shop, automatic direction finders are mounted on a revolving test stand and checked against a General Radio Type 805-B Standard-Signal Generator. Here lead mechanic Gerard Miller tests the set with a Type 726-A Vacuum-Tube Voltmeter.
Figure 2. The Type 631-B Strobotac is used to check vibrator reeds by James Hargreaves, lead mechanic in radio-overhaul shop.

radio shops cover all frequencies in the high frequency band.

The Signal Generators are but two of the pieces of General Radio Co. equipment in use by this great airline. Also in constant use in their shops at La Guardia are the Type 650-A Impedance Bridge, the Type 631-B Strobotac, the Type 726-A Vacuum Tube Voltmeter, and the Type 813-A Audio Oscillator.

The Voltmeter and the Bridge have come to be highly important pieces of equipment in the routine operation of the shop. While the Impedance Bridge is actually a laboratory instrument, American radio engineers have found it to have an important daily use in the testing of various parts. With it the capacity of condensers, resistance of resistors, and inductance of coils can be immediately ascertained.

A stroboscope is not only a great time and trouble saver, but has come to be^a true necessity in the modern radio shop. American Airlines has in its Radio Overhaul a General Radio Strobotac, Type 631-B. This piece of equipment is small enough and light enough to be handily moved to wherever it might be needed. It is in constant use by American radio repairmen, who bring it into play in analyzing anything that moves. With it vibrator reeds are checked for proper contact, armatures are searched for correct brush contact, and rotating gyroscopes are inspected.

The Strobotac is frequently used in the American shops to check items which do not in themselves move, but which are affected by movement. This is done on a "shaker table". The table is mounted on shock mounts, and a high speed air motor with an attached eccentric weight is connected to the table itself. An item which might be affected by vibration is put on the table. Then the table is put into motion and the item in question scanned with the Strobotac, which will show up any cracks or bad connections caused by the stress of the motion.

Possibly the best record set for American Airlines by a General Radio product is that of the Type 813-A Audio Oscillator. This Oscillator, which transmits a constant 1000 cycle tone, was chosen by American for use in their range stations in Mexico. There are five such stations in the company's Mexican leg. These stations were put into operation on September 5, 1942. On March 11, 1946, the first one of the Oscillators to need repair was received in the American Airlines shops in New York. This makes a total of 41 months of constant service by five General Radio Audio Oscillators before one of them needed adjustment.

Text and photographs for this article were furnished through the courtesy of American Airlines, Inc.

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