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September 1932 Radio News[Table of Contents]
These articles are scanned and OCRed from old editions of the Radio & Television News magazine. Here is a list of the Radio & Television News articles I have already posted. All copyrights are hereby acknowledged.
This past Monday marks the first anniversary of the massive forest fire in the White Mountains of Arizona that claimed the lives of 19 "Hotshot" firefighters, so I thought maybe this story from a 1932 edition of Radio News would be an appropriate recognition of their sacrifice. Firefighters of all specialties have relied on radio communications nearly since its inception, and particularly once battery-powered versions became available for portability. It is hard to imagine a time when such a convenience - even a necessity - was not part of the standard firefighting outfit. Nowadays the radios are compact and clip onto a shoulder lapel, but in 1932 the vacuum tubes, large transformers and batteries meant even a primitive radio was in the form of a harness-mounted manpack (a word not yet coined at the time). The portable half-wave dipole antenna in the picture looks almost exactly like ones I have see today advertised in QST magazine.
When the Erstwhile Friend of Man Turns Enemy
Fire in the forests is a cataclysm so awful and so hard to escape that all of the living kingdoms are affected by it. The plant kingdom, attached as it is to mother earth, finds no escape except as is afforded by man's ingenuity in stopping the progress of the flames. Bacteria and insects are destroyed, it is true, but their mobile abilities soon cause replacement. Animals and man, equipped as they are with instinct and intelligence, fear woods fires as a common enemy and often flee side by side. Radio is now giving man new tools and new speed in fighting fire in its first stages, while it is still small, to prevent widespread conflagrations.
The forest Ranger up to this time had to rely upon primitive communication methods in fighting great fires in our National forests. He has hit the trail to carry word of a conflagration either by horse or afoot. But now radio comes to the rescue with two portable transmitter-receivers that contact headquarters within a few seconds bringing necessary help and equipment in short order
By George A. Duthie*
Portable radio receiver-transmitters for emergency communication in the national forests is a recent achievement of the U. S. Forest Service. It is an achievement hailed with enthusiasm by forest officers. Since the day when the radio telephone was announced forest rangers have dreamed daydreams of the time when a ranger on leaving for a trip to the back country, would slip a radiophone into his pack, along with his grub, and be able to report back to headquarters from the deep woods or from beyond the high ranges. "An impractical, futile dream," said experts who were appealed to for help to solve the problem. But the ranger "amateurs" unfettered by knowledge of radio engineering that recognized this futility, substituted enthusiasm for learning, and trial-and-error experiments for fundamental research, to achieve the impossible. The dream has now come true. Its final achievement was marked by a recent order for the construction of 105 portable and 27 semi-portable radio sets of a special Forest Service design. It is the first step toward equipping the field force with this long-sought solution for its emergency communication problems. It is the culmination of 14 years of research on radio transmitter-receiver sets that can be carried about in the forests and set up at will for temporary emergency service.
Although both sets are portable radio transmitter-receivers, the smaller instrument is referred to as the "portable" because it is so light that it can be carried about in a ranger's back-pack. It weighs only 10 3/4 pounds including batteries and antenna and is literally a hand radio set which the forester can carry right along with him as he works (See Figure 1). For the sake of lightness the phone transmitter is dispensed with and the instrument transmits code only - but it receives voice! The larger set is called "semi-portable" to distinguish it from the portable. It is a radio-phone (receiving and transmitting) handling voice as well as code. It weighs about 60 pounds and may readily be transported any place where a pack-horse can go.
In the forests the communication problem is present on almost every job. Whether it is fire patrol or fire suppression, building roads or trails cruising timber, rescuing lost persons or inspecting range, there is always need for communication. The work is spread over thousands of square miles of rough timbered territory and the efficiency and speed with which it is done is directly affected by the efficiency of the communication system in quite the same way that field operation of an army depends upon its communication service. Between points of permanent activity, such as ranger headquarters and lookout stations, telephone lines have already been built. There are 40,000 miles of government-owned lines in the forests, and approximately 100,000 miles of commercial and private lines, all of which are available for official use and yet less than 20 percent. of the territory lies within convenient reach of a telephone line. There are 200,000 square miles of territory without communication service except by messenger or, temporarily, by stringing insulated emergency wire.
Forest Service Photos
The Ranger's Portable Radio Pack
Figure 1. Special forest service radio pack, weight ten pounds, range ten miles
The use of the latter type of communication has been confined principally to large fires where it has rendered valuable aid, but it is not satisfactory because it is slow, expensive and generally inadequate. A crew of men will toil for days to reach the fire camp with an emergency line and the pressing need for it is sometimes past before it is completed. It is costly because it is difficult to lay down and maintain, and frequently the wire is not worth the cost of salvage after the emergency is over. It is inadequate because it furnishes connections only to the supply base. A wire line cannot be maintained to the rapidly changing fire front where sweating crews are waging a real battle. It is here that the communication need is most acute, for the fire fighters may be frantically calling for help but their message will speed no faster than a runner can travel. The work of the various crews attacking the fire on several sectors must be correlated, but the officer in charge can receive his reports and send out instructions only by a messenger who may take an hour (or many hours) to reach his objective.
Minutes Count at a Fire
The radio solves this problem, for it will move right along with the crews. It takes but a few minutes to set up the instruments and its message reports the situation to headquarters at the instant - not the situation as it was an hour or five or ten hours ago. I have timed a forest officer who, without hurry, unpacked a portable set, hung up his antenna between two trees, and established communication with a distant station in twelve minutes. In fire suppression work minutes count and that is why the radiophone is regarded as an achievement of great importance in forest protection. The patrolman or the "smoke chaser" hunting incipient fires or the crew boss on the fire line may now carry his communication with him and contact headquarters at will (See Figure 2).
How often do small fires become raging conflagrations during the interval while re-enforcements are being summoned? Perhaps a margin of thirty minutes in arrival time would have been sufficient to stop the fire in its first run. The portable set will give the forest officers the benefit of that margin.
Radio will not, however, replace the telephone lines for regular service between permanent stations. It will supplement the wire system and provide temporary emergency communication for 80 percent. of the forest territory that is out-of-reach of the wire lines. The equipment designed by the Forest Service for its work consists of two short-wave sets; a 3-tube portable for the patrolman's pack, light, compact and sturdy, which transmits code and receives voice; and a 6-tube semi-portable set which can be readily transported by pack horse or automobile and which transmits and receives either code or voice.
The outstanding features of the portable set are its light weight; its compactness; its simple, rugged construction; and its low cost. These four features, together with dependable service under the peculiar atmospheric conditions encountered in forests, comprise the essential requirements that the set had to meet before it could be adopted. Its power plant consists of a single 140-volt B battery and an A battery of two flashlight cells which have a life of seven hours. The power of the transmitter is too small to be measured, but its C.W. range is from 10 to 15 miles - which is enough for its purpose. Exclusive of B battery and antenna, the entire equipment is contained in an aluminum box 6 by 8 by 9 inches. It weighs but a trifle more than 10 pounds and can be fabricated for $50.
Semi-portable Ranger Set
Set-up at Field Headquarters
Figure 3. This semi-portable radiophone can be carried by motor or pack horse and set-up in a safe location near the fire to contact rangers on the fire line
The semi-portable radiophone (See Figure 3) weighs 60 pounds and has a range of 10 miles for voice and 20 miles for code. Its power consists of two 200-volt B batteries and an A battery of three No.6 dry-cells. It is constructed with the same rugged simplicity as the portable set. While it is too heavy for a man to pack far over mountain trails, it will stand packing on a horse or by automobile over rough roads.
The scheme of use for the two sets is to place the semi-portable at the lookout station, the fire camp or construction camp or any other field job when the short period of occupancy of the camp and the distance from a telephone line renders wire communication unavailable. The portables will be carried by the field-going men who are traveling on foot or by saddle horse. At the lookout station, the radiophone will act as central station to which the "smoke chasers," who are dispatched to investigate smokes, will report back with the portable C.W. sets. On large fires, the crew bosses and patrolmen will carry the portables on the fire line for reporting to the central camp where a dispatcher will be constantly on the air with a semi-portable radiophone. A contemplated development for camp set-up is an amplified receiver which will pick up the signals from the field sets and make them audible without keeping the dispatcher with his ears glued to the headphones.
The history of the development of this equipment, like that of most new equipment, has been one of long research, many discouragements, threatened abandonment and a slow breaking down of the main obstacles and final success in a climax of feverish enthusiasm. The first attempt to use radio in forest work was made immediately following the World War with long-wave equipment. It was a complete failure but it served to discover some of the special problems of radio transmission peculiar to the conditions in the forests. These problems, for some years, appeared to be insurmountable obstacles the adaptation of radio to forest communication.
The chief Obstacles Were:
1. The absorption of radio energy by the green timber, which to overcome would, it seemed, require much more power than could be provided in a portable set. 2. The shadow effects of rough topography. Under high mountains there might be "dead spots" from which low-power radio signals could not emerge. 3. The deadening effect of static and fading in the mountainous country, an effect that varies for different wavelengths and for different periods of the day. 4. The difficulty of erecting long antennas in the forest where the thicket of undergrowth and swaying branches of trees would interfere. 5. The mechanical difficulty of constructing a set with a combination of extremely light weight and the sturdy construction which is necessary to withstand the hazards of transportation in a wilderness country. 6. Simplicity of design which will obviate delicate adjustments and tuning so that the apparatus can be operated by inexperienced and unskilled men.
It would be a simple matter to build radio sets that would overcome any one of these obstacles, but to successfully meet all of them in combination presented a discouraging, yes even hopeless, problem for many years.
Inside the Portable
Figure 6. This inner view shows the details of the c.w. transmitter-receiver illustrating compact arrangement.
Following the failure of the first attempt to use radio, nothing more was done for several years save that some of the more radio-minded members of the service kept the idea simmering until in 1927, Dwight L. Beatty, an inspector, made some interesting demonstrations with a small short-wave "bread-board" set which resulted in his detachment from other duties and his full-time assignment to the radio problem.
Beatty first canvassed the field of commercial sets, especially airplane radio, but found nothing that would meet the forest requirements. Radio engineers and experts were interviewed, but they offered no suggestions more than to say that the problem opened up a field of research in which they could see little opportunity for fruitful work. It became obvious, therefore, that if radio-in-the-woods was to become possible, it must come through amateur experimentation.
So Beatty set to work. At the outset, his purpose was to discover the effect of absorption of radio energy by green timber and the nature of the interference encountered in the shadow of rough topography. He found that the loss in signal strength, in timber as compared to an open setting, ranged as high as 35 percent. He also discovered that the shadow effect and fading in the mountains varied in wide limits for different wavelengths and that these variations changed during different periods of the day. For example a 91-meter signal at noon might be completely smothered but after 4 o'clock it picked up in volume while from the same station a 55-meter signal which was strong, throughout the day, faded away at night. He found also that some types of equipment were more sensitive to these effects than others, which led him into extensive tests of different combinations of parts and hook-ups. He worked diligently for three years, endlessly building sets, testing them under field conditions, tearing them down, rearranging and reconstructing, always searching for improved equipment that would improve efficiency and better provide the specified qualities of lightness, compactness, strong construction, efficiency of performance under forest conditions, simple design and low cost. Only standard parts were used so that there is nothing new about the equipment except its design and assembly. In each alteration of design greater simplicity was sought. Every dispensable part was eliminated to reduce weight.
By the summer of 1930, Beatty had developed two sets: a semi-portable radio-phone weighing approximately 80 pounds (including batteries and antenna) and a portable set weighing less than 20 pounds. The antennas employed with both types were the same. It was a counterpoise system consisting of an antenna wire stretched approximately 15 feet from the ground between two light masts and a counterpoise wire at 3 1/2 feet, stretched parallel to the antenna wire. The length of the system varied from 73 to 90 meters, according to the frequency in use.
Bottom View of the Two Ranger Units
Figure 5a - The underneath view of the sub-panel of the semi-portable transmitter-receiver.
Figure 5b - The same view of the portable unit which may be carried on the ranger's back
The Power-Feed Antenna
Figure 4. This antenna was developed for the special use of the forest service radio-phone.
Both sets were given extensive field tests in 1930 in the Columbia forest in southern Washington. Seven of the portables were placed in service with road and trail crews and fire patrolmen, and were used throughout the summer. Two of them were used at the Dog Mountain fire, where a large number of messages were exchanged during the course of the fire. Although these sets were used by men inexperienced in radio and without training in the use of code, the records of the use of the seven instruments showed better than 94 percent successful performance. The 6 percent failures were due, almost entirely, to weather conditions.
In spite of this good record there were still many problems to be worked out before the equipment could be voted a success under all conditions. The bugbear of absorption and shadows had been largely overcome, but the equipment was too heavy and the aerial too cumbersome. Therefore, when Beatty dropped the work in early 1931 there was grave danger that it would be discontinued. It was rescued from the discard by F. V. Horton, assistant regional forester of Portland, who put A. Gael Simson in charge of the work.
Simson was employed in forest research but he was an amateur radio enthusiast, having served as a radio operator in the Navy during the World War. He was given two assistants, Harold K. Lawson, a young logging engineer who was employed on timber sales work and road building, and W. F. Squibb, a student of electrical engineering at Washington State College, who accepted short-term summer employment as a ranger guard. All of these men are amateur radio fans. They took up the job where Beatty left it and tackled the unsolved problems with that intense enthusiasm that only an amateur knows. Three months after they started work, I happened in at headquarters one Sunday morning and finding the whole crew hard at work I remarked to Simson: "Your assistants seem to be pretty much interested in their job." "To a fault," he replied tersely, "Lawson, there, is a logging engineer. He thinks the right time to begin the day is 7 a.m., but Squib is a student; he likes to work at night and is ready to call it a day about midnight, and between the two they work me a mighty long shift." So the testing, experimenting, and rebuilding went on, almost feverishly, throughout the summer. Both sets shriveled in size and weight and increased in reliable performance. Perhaps the most outstanding improvement, however, was in the antenna.
The counterpoise system was unsatisfactory because it is clumsy and unhandy to erect. The two wires must be taut, parallel and reasonably level. On rough ground or in dense undergrowth, finding a suitable place to erect it frequently presented a serious problem. An opening may be readily found where a single antenna wire can be stretched where it is quite impossible to find one where two wires could be stretched 12 feet apart in the clear. It was, therefore, decided to make a special effort to develop a single-wire system and the result is a power-feed antenna of very simple design (See Figure 4). The length of the antenna is made to correspond to the frequency of the transmitter. A loading coil, fitted with a terminal attachment for the feeder wire, is inserted at the correct point to give the best results. This point has been found to be about 14 percent. "off-center." The coil reduced the length of the antenna to about 70 feet, which greatly simplifies its erection. Since the point of attachment of the feeder wire is definitely fixed by the terminal post on the coil, no particular care in erecting the power-feed antenna is necessary, excepting to be sure it is in-the-clear of branches or other interference. It has the additional advantage of being several pounds lighter than the counterpoise system, which is an important contribution to the success of the project.
The innumerable field tests of the past year have brought a great deal of new information about the selection of a site for the set-up. It was found, for instance, that a shift of 200 yards from the base of an overshadowing ridge may increase the strength of the signals as much as two points in a scale of ten, of which seven points represent the normal degree of loudness that the receiving operator desires from a headphone clamped to his ears. Another subject of inquiry was how readily inexperienced men could be expected to become proficient in the use of the C.W. portable set. Many of the men who may have occasion to use it will be temporary laborers, for whom no preliminary training in sending code is possible. It is really remarkable how quickly untrained men, who may never before have seen a telegraph key used, can pick up the use of the code. A monitor is built into the receiver which permits the operator to hear his own signals. This steadies his sending and provides a constant check on its quality. With a surprisingly small amount of practice he can send intelligible code signals with the tiny telegraph key. As a final demonstration test, a young laborer employed on trail construction was given about 30 minutes coaching and was instructed to send a dictated message. In 46 minutes he set up the radio, coded the message, sent it to a distant station, had it repeated back to him by voice, and packed up the radio ready for transportation. This demonstration silenced all doubts whether the rank and file of officers and temporary employees would or would not be able to use the C.W. sets without long preliminary training.
Figure 2 - Smoke Chaser with Portable Set
If light weight is the first essential, sturdy construction is a second requisite of almost equal importance. The vibrations, knocks, and jolts of transportation by truck, pack-horse or man-pack would quickly disable the delicate meters which are usually considered indispensable in a radio transmitter. All delicate parts and fragile wiring had to be eliminated to insure dependable performance of the equipment when it reaches the field. It was found possible to dispense with all meters (except a small voltmeter which can be successfully cushioned in sponge rubber). The simple arrangement of the parts, to reduce wiring and strength of all connections, were worked out with great care (See Figure 5), and the tubes are set in spring sockets and cushioned with sponge rubber (See Figure 6) so that they need not be removed during transportation. Both sets have been subjected to every kind of stress they may meet with in field use and have stood up under the roughest kind of treatment.
Finally the designers decided to give the semi-portable radiophone an accident test, just to see how much it would stand and where failure might first be expected. Four of the six tubes were tied to their sockets with rubber, the remaining tubes were left free. The set was then dropped 14 feet to the ground! The jolt caused the two free tubes to jump from their sockets and to break. The broken glass was shaken out of the set, the two broken tubes replaced and it was put "on-the-air" without further adjustment and a conversation carried on with a station 60 miles away. The sets have certainly been built for rough going!
The experimental stage is now completed. Every conceivable test for weaknesses that might develop has been made and as weak points have developed changes were made to remedy them. Radio is now ready for the field, the forests, and a thousand ranger officers are reaching for it. Approximately 150 sets will be available this year, and these will be issued to a few forests where the need for them seems most urgent and where good opportunity exists for exacting field tryouts. It is to be expected that some failures may develop, for the sets will be used in every kind of climatic situation from the humid forests of northern Washington to dry deserts of Arizona and California, from sea level to the timberline country of the Continental Divide, in heat and cold and from mountain top to the bottom of deep canyons. Some situations may be found where special equipment or change of design will be necessary, but the versatility they have already displayed in experimental tests gives confidence in their adaptability to almost any situation. Long before sufficient equipment to supply all of the forests can be had, there will be opportunity to discover any peculiar situations where special adaptations will be necessary.
A problem which can be foreseen, but upon which no work has as yet been done, is regulation of traffic in the channels assigned to the Forest Service. When 147 forests are equipped with radiophones and each forest has several central-camp stations receiving reports from several individuals using portable sets, it can be foreseen that, without regulation, there might be chaos. The very-low power and range of the instruments will help to hold this situation in check to some extent, but some additional regulation will doubtless be necessary so that all the men will not try to talk at once.
* Forest Service, U.S. Department of Agriculture.
Posted July 4, 2014