"Say again." That phrase is heard often in telephony conversations both wired and wireless. It was coined near the end of World War II by Air Corpsman 2nd Lt. Byron A. Susan, as reported in the January 1945 edition of Radio Craft magazine. Lt. Susan was responsible for setting standards for "radio phraseology" to eliminate ambiguity between aviators and ground forces. "Say again" replaced "Repeat" because the latter is an artillery term used to order the repeat of a gun salvo.
Air Corps Radio Phraseology Training
By 2nd Lt. Byron A. Susan
Air Transport Command
Lt. Susan, Air Corps phraseology instructor.
Specially-designed amplifier for use in teaching students proper phraseology during tower-to-plane communications.
A bit of ingenuity, a broken-down radio set, and two hand mikes normally used in aircraft, enabled the construction of an effective training aid for the author's course in radio phraseology.
In the business of flying, where more and more the correct use of the right word at the right time gains in importance, this clever training aid enables the student to learn the correct way as well as familiarize himself with checking in and out with radio control towers.
A mike in the hand of the instructor, who acts as the tower, and another mike in the hand of the student, as the pilot, enables them to simulate conditions as they would be encountered in actual flight. As their voices are heard, the entire class acts as the critic.
A few months past, when the British and U. S. Governments got together and agreed on one set of radio phraseology, it became necessary to instruct our pilots in the new vocabulary. Not that the words were new, but words which had been picked up and had gained common usage, were dropped in cases where they failed to mean what they stated. For example, "over" is now used when one desires the other transmitting to come in. "This is" has been substituted for the former "from" which was difficult to understand. "Say again" is now used instead of "repeat," as the latter is an artillery term used to repeat a salvo. These are but a few examples of the many term changes that necessitate the course in radio phraseology.
This training aid, though extremely simple, is highly effective and is daily proving its advantages to enthusiastic classes. The amplifier has been assembled on a small chassis, large enough to accommodate the component parts. No specific arrangement of parts need be specified due to the fact that there are no parts which would be adversely affected by inductive pickup. Since the microphone input circuit is of low impedance, there is no pickup due to the field of the power transformer.
Fig. 1. Circuit diagram of amplifier. An Army aircraft microphone, connected to a two-conductor plug, is used.
R1 - 500,000 ohm, 1 w. res.
R2 - .5 megohm, pot.
R3 -2200 ohm, 1/2 w. res.
R4 - 1 megohm, 1/2 w. res.
R5 - 200,000 ohm, 1/2 w. res.
R6 - 300,000 ohm, 1/2 w. res.
R7, R9 - 150 ohm, 1 w. res.
R8 - 10 ohm, 1 w. res.
R10 - 25,000 ohm, 1 w. res.
C1 - .1 μfd. @ 400 v. tub. cond.
C2, C5 - 25 μfd. @ 25 v. tub. cond.
C3 - .25 μfd. @ 600 v. tub. cond.
C4 - .1 μfd. @ 600 v. tub cond.
C6 - 80 μfd. @ 450 v. elec. cond.
C7 - 20 μfd. @ 450 v. elec. cond.
By incorporating the constants as shown in Fig 1, the average gain of the amplifier is approximately 56 db. from 500-ohm input to 4-ohm output. The amplifier gain control will provide for adequate output level to cover a class of 50 men in a room 15 by 30 feet when in the two-thirds open position. (Audio-Taper control is used.) The undistorted output with a plate voltage of 300 and a screen voltage of 250 is 5.0 watts when the speaker is matched correctly and the tube is feeding into a load resistance of 5,000 ohms.
It is to be noted also, that the polarizing voltage for the microphone is obtained from the bias resistors in the output stage. No filtering other than that shown is required. Low polarizing voltage eliminates acoustic feedback to a large extent. The original model was built in a small wooden cabinet with no controls other than the switch and volume control on the front panel. The two microphone jacks were also located thereon. One mike with a standard length cord is plugged in and is used by the instructor. A second mike is also plugged in, through two or three six-foot extension cords, as required, and passed out to members of the class. When plugged in and turned on, the device becomes the medium through which the entire class may hear the two-way conversation between the instructor and student, who, alternately become pilot and ground-station operator.
The classroom practice, with the use of this unique training aid, has made the 20th Ferrying Group's radio phraseology course one of the most interesting, as well as informative phases in the curriculum of students attending the Ferrying Division training school at the Nashville, Tennessee base.
Posted July 29, 2014