September 1932 Radio News
Wax nostalgic about and learn from the history of early
electronics. See articles from
Radio & Television News, published 1919-1959. All copyrights hereby
"Don't forget who brung you to the dance," is a variation of the
old adage that admonishes you to remember who/what it was that provided
the opportunity to be where you are now. It aptly applies to radio
communications of all sorts. This short article from a 1932 edition
of Radio News discusses the advent of radio beacon installations
across America to facilitate air navigation during inclement weather.
Before there was a Federal Aviation Administration (FAA), the Department
of Commerce handled commercial air traffic for passenger and cargo
payloads. Aviation was on the verge of becoming a very profitable
Douglas DC-3 would make that happen in 1935) and it was necessary
controls to ensure safety and smooth operations. Early direction
finding equipment used a directional loop antenna to indicate the
bearing (not necessarily the heading, due to winds) to a ground-based
broadcast station. Audible signals indicated whether the aircraft
location was to the left or right of the station. Visual indicators
would later provide course deviation information. Aside from GPS,
radio beacon navigation is fundamentally the same today as it was
in 1932, only with more precision, greater reliability, and more
reference stations. If you don't know a VORTAC station when you
see it, take a look to the left - yep, that's what those things
you see sitting in fields all over America are!
...in Private and Transport Flying
By John B. Brennan, Jr.
Modern airport and 'plane radio equipment not only provides
an operations communication medium, but also a guide for
blind flying and landing under weather conditions which
would otherwise offer an insurmountable hazard to 'planes,
pilots and passengers.
Picture yourself on a plane, one of those big
tri-motored affairs, which has just taken off from the Newark
Airport, bound for Cleveland. Although you may not have known it,
the pilot, previous to the take-off, scanned the weather dispatches
at the Operations Office and found that he would have good weather
along the major portion of his course but on arriving in the vicinity
of Cleveland he might expect haze and fog.
Once up in the air his co-pilot, who is also the radio operator,
has donned the headphones, switched on the radio receiver and has
tuned it in to the signals being transmitted by the radio range
beacons, of which, on his course, there are three; one at New Brunswick,
New Jersey, one at Bellefonte, Pennsylvania, and the other at Cleveland,
Ohio, all on direct route.
In clear weather it is not necessary to depend on the radio range
beacons for an indication of the true course since visual searchlight
beacons and markers on the ground at these searchlight points are
situated along the course every ten miles. Therefore, having satisfied
himself that the radio receiver is functioning properly the co-pilot
tunes it to another wavelength so that he may listen to the many
radio ground stations located along the path of his course and to
the major aeronautical ground stations located at the scheduled
stopping points along his route and which are a part of the vast
radio chain system operated by the airways organization which employs
Thus, speeding along at some ninety to one hundred and ten miles
an hour, the plane in which you are comfortably seated is always
in constant communication with some radio station on the ground
and your pilots are being advised periodically of flying conditions
ahead of them, i.e., visibility, height of ceiling, force and direction
of the wind and so forth.
The Voice and Ears of Transport 'Planes
The relief pilot functions as radio operator, receiving
weather reports, beacon signals and landing instructions.
By means of his transmitter he keeps ground stations informed
of the 'plane's position and carries on communications incidental
Then, too, the co-pilot keeps the ground stations posted on the
progress of the flight of your plane and every fifteen minutes he
switches on his radio transmitter and reports his position along
As you near Cleveland the threatened foggy weather has materialized
and you fly into a blanket of fog so thick that it is difficult
to see the tips of the monstrous wings of the plane. Spotting a
position on the ground is out of the question under these conditions
and it is here that the radio range beacons come into play.
Tuning to the beacon wavelength the operator listens for the
characteristic signal, a long dash, which will tell him that he
is on his correct course. If the plane is bearing to one side of
the beacon path of signals then he will hear a dot and a dash while
if on the other side he hears a dash and a dot. This when the dot
dash and the dash dot converge into one long dash that the pilot
knows that' he is bearing along the true course.
Intermediate marker radio beacons advise him that he is nearing
Cleveland and through a hole in the misty blanket he comes down
to pick out familiar landmarks on the ground. By this time the visual
beacons are sending out their friendly flashes of piercing light
and after picking up the boundary lights at the Cleveland Airport
he circles the field and comes in for a perfect three-point landing.
Now lets change the scene and see what has been happening at
the Cleveland ground station while the plane is approaching it through
its blanket of fog. In the first place, before the plane reached
the fog area the radio dispatcher at Cleveland Airport advised the
pilot of the plane when he might expect to meet up with this impenetrable
blanket. Because the pilot has been advising him of his position
as he progressed along the route, the dispatcher knows exactly where
the plane is. By means of little pins with the numbers of the various
planes aloft the dispatcher marks off their position on a large
map of the several air routes which converge at his airport.
In addition to his job of keeping the planes advised of the weather
they are flying into the dispatcher handles the routine messages
concerning the taking off and arrival of planes at his and other
Thus you have been given a small picture of the radio drama being
enacted daily at the hundreds of airports which dot the country
and the countless planes which fly the air routes.
Today the country is literally webbed with these air routes.
A glance at Figure 1 will show that there are two transcontinental
routes, one extending by way of New York to Chicago; Omaha, Salt
Lake City and thence westward across the Rockies to Oakland, California.
Another, starting at New York takes a more southerly route after
leaving Chicago and terminates at Los Angeles, going by way of Kansas
City; Amarillo, Texas; Albuquerque, New Mexico, and Kingman, Arizona.
On the West Coast a regularly established air route has terminals
at Seattle and San Diego, with intermediate stops at such places
as Portland, San Francisco and Los Angeles in either direction.
On the East Coast one route goes to Buffalo by way of Albany,
another goes to Boston by way of Hartford while still another goes
to the Central and South American countries by way of Washington;
Charleston, South Carolina; Jacksonville and Miami, Florida, and
On December first, 1930, there were forty radio range beacon
stations in operation with an additional nine due to be completed
and in operation by January first, 1931. These stations are of the
aural type, sending out the characteristic dot dash, dash dot signal.
They are shown in Figure 2. According to information made available
by the U. S. Department of Commerce there were to be twenty-one
radio range beacon stations of the visual type in operation by June
of 1931, with forty-one others of this type projected for installation
and operation in the then near future.
Aeronautical radio apparatus may be divided roughly into two
classes, i.e., the equipment used on the plane and the equipment
used on the ground. In both cases these classes may be further subdivided
into the transmitting and receiving equipment used at both terminals
of the two-way communication system.
Aviation Radio Equipment
For use in transport airplanes there has been developed a radio
transmitter which is both light in weight and compact. Known as
the Western Electric 10A radio transmitter, it has a carrier of
fifty watts and is arranged for substantially complete voice modulation.
It covers the range from 1,500 to 6.000 kilocycles.
Government Air Radio Services
Figure 1 - The areas enclosed within circle s denote
coverage by U.S. Department of Commerce transmitters which
broadcast, at least hourly, weather reports, and other information
for flyers. Unshaded areas denote stations either under
construction or proposed.
Figure 2 - Radio beacon transmitters are distributed
at short intervals along the more important airways, as
indicated on this map.
The operating frequency selected is maintained to within plus
or minus .025% of the assigned value by means of a quality-crystal
controlled oscillator. This accuracy is maintained even at extremes
of flying weather by virtue of the fact that the quartz crystal
is temperature controlled by a thermostat of the mercury-column,
contact making type. Space in the transmitter is provided for two
of these frequency controls.
The crystal-controlled oscillator employs a tube of the five-watt
variety which generates oscillations at a frequency which is one-half
of that actually radiated by the antenna. Coupled to the output
of the oscillator is a second five-watt tube which acts as a frequency
doubler. This stage in turn is coupled to the modulating power amplifier
which consists of a fifty-watt tube, Rice neutralized. The modulation
system consists of three fifty-watt tubes connected in parallel
whose grid circuits are energized by a special type of microphone
Power for the transmitter may be supplied from either a dynamotor
which is run from the ship's storage battery or from a special wind-driven
generator. The twelve-volt ship's battery supplies filament excitation
while the dynamotor or generator supplies 400 milliamperes at 1050
volts for plate and grid bias supply. Connection from the transmitter
to the power supply is made by means of a specially designed plug
provided with locking pins and a lock ring.
Wavelengths for Aviation
The transmission of signals to aircraft is in the case of transport
.service accomplished at the short wavelengths, say in the neighborhood
of fifty meters, while for itinerant aircraft transmission from
the ground to the plane takes place between 200 and 450 meters.
Airport transmitters are assigned the frequency of 278 kc. while
weather report stations usually transmit on frequencies lying in
the range from 240 to 350 kc. Thus, to cover this wide range of
wavelengths two separate Western Electric receivers have been developed.
Essentially, both receivers look alike in outward and internal appearance
excepting that one is designed for use at frequencies between 1500
to 6000 kc. while the other works between the frequencies of 230
to 500 kc. The short-wave receiver employs three stages of screen-grid
radio-frequency amplification, a space-charge detector and one stage
of audio-frequency amplification. The long-wave receiver employs
one less r.f. stage and one more a.f. stage. They are designed to
work with headphones ... not loud speakers.
Power for these receivers is also obtained from a dynamotor as
in the case of the transmitter, the plate potential being 200 volts
and the filament voltage being obtained directly from the 12-volt
Radio Equipment for Private Aircraft
Figure 3 - Here are shown the Western Electric transmitter
(left) and receiver installed in a plane, ready for operation.
Usually located in an out-of-the-way corner, the receiver
is tuned by remote control from the pilot's position. The
remote control cable is shown here, attached to the front
of the receiver
Both the transmitter and the two receivers are mounted on trays
which are constructed in such a manner as to provide a high degree
of shock absorption, thus guarding against unduly severe mechanical
strain due to vibration and landing shocks.
Usually both the transmitting and receiving equipment are located
in some unused portion of the plane's fuselage and therefore a remote-control
tuning apparatus is provided in the pilot's cockpit.
For itinerant aircraft a low-powered transmitter (Figure 3) has
been developed to meet the especial requirements of this branch
of the flying service. This transmitter, in design is much like
that intended for the use of the transport planes, the difference
being that instead of having a fifty-watt carrier this one has only
a ten-watt output. The transmitter consists of a quartz crystal
oscillator, a modulating amplifier and one stage of audio-frequency
amplification. The ten-watt output is substantially completely modulated
and the tuning range of the transmitter is from 3000 kc. to 6500
In the transmitter is contained an antenna transfer relay by
means of which the antenna may be connected to either the transmitter
or the receiver. Power for the operation of this transmitter is
obtained from a dynamotor driven from the ship's 12-volt storage
battery. It delivers 525 volts d.c.
As is to be expected, the ground station which is used to communicate
with planes operating in the transport service over the established
chain airways is more elaborate and more powerful than the plane
The ground transmitter produces a carrier power of 400 watts
which as in the case of the plane transmitter is substantially completely
voice modulated. It is so designed that it may be adjusted for operation
on any frequency between 1500 and 6000 kilocycles.
This transmitter comprises the following units: a crystal-controlled
oscillator, a frequency doubler, a modulating amplifier an audio-frequency
amplifier and a power amplifier. In the oscillator and frequency-doubler
stages five-watt tubes are employed, while in the modulating amplifier
stage a fifty-watt tube is used. The radio-frequency power amplifier
employs a single 1000-watt (1kw.) radiation cooled tube which operates
at a plate potential of 2500 volts. The audio amplifier system is
similar to the plane unit in that it uses three fifty-watt tubes
connected in parallel and operated by a special design of microphone.
The rectifier system works from a 220-volt three-phase 50 or
60 cycle line and supplies potentials on the order of 2500, 1000,
200, and 55 volts d.c. and 10 volts a.c. Rectification is obtained
by means of seven low voltage mercury vapor rectifier tubes.
At airports which are not on the regular chain airways and where
there is the desire to provide radio communication facilities to
itinerant aircraft the ground station is not nearly so elaborate.
The Federal Radio Commission has stipulated that such ground stations
operate on a frequency of 278 kc., and that their carrier output
be restricted to 15 watts. Actually the transmitter described here
is rated at ten watts output. It consists of a crystal-controlled
oscillator, a modulating power amplifier, a speech power amplifier,
a full-wave rectifier, filament supply and all the necessary control
The purpose of such a transmitter is to provide communication
to pilots on planes in the vicinity of or nearing the airport so
equipped. It is not intended for long range communication.
The maps which accompany this paper will serve to illustrate
that fact that a pilot, whether he be of the itinerant or transport
class and whose plane is equipped with the prescribed radio apparatus,
need never be out of touch with the ground, regardless of whether
he start out on a flight to a neighboring town or a more pretentious
Every day flying becomes increasingly safer because radio provides
the long arm of communication as no other agency can, to keep the
pilot informed of flying conditions ahead, landing facilities at
unfamiliar airports and the other thousand and one things which
only pilots want to know when they are out of touch with the rest
Posted May 22, 2014