"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
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
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,
R1 - 500,000 ohm, 1 w. res.
R2 - .5
R3 -2200 ohm, 1/2 w. res.
- 1 megohm, 1/2 w. res.
R5 - 200,000 ohm, 1/2 w. res.
R6 - 300,000 ohm, 1/2 w. res.
- 150 ohm, 1 w. res.
R8 - 10 ohm, 1 w. res.
- 25,000 ohm, 1 w. res.
C1 - .1 μfd. @ 400 v. tub.
C2, C5 - 25 μfd. @ 25 v. tub.
C3 - .25 μfd. @ 600 v. tub. cond.
- .1 μfd. @ 600 v. tub cond.
C6 - 80 μfd. @
450 v. elec. cond.
C7 - 20 μfd. @ 450 v. elec.
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