The radio detectives
2t»«W ^m IK' '■ '%1 BPP^^ ^^KtUtint> •"*"'• ^ < ^ jyijiif THE RADIO DETECTIVES BY A. HYATT VERRILL THE RADIO DETECTIVES THE RADIO DETECTIVES UNDER THE SEA THE RADIO DETECTIVES SOUTHWARD BOUND THE DEEP SEA HUNTERS THE BOOK OF THE MOTOR BOAT ISLES OF SPICE AND PALM D. APPLETON AND COMPANY Publishers New York 200 B "help! send for help!" THE RADIO DETECTIVES BY A. HYATT VERRILL AUTHOR OF "THE DEEP SEA HUNTERS," "ISLES OF SPICE AND PALM," "THE BOOK OF THE MOTOR BOAT," ETC. D. APPLETON AND COMPANY NEW YORK : : 1922 : : LONDON COPYRIGHT, 1922, BY D. APPLETON AND COMPANY PRINTED IN THE WNITED STATES OF AMEBICA ©CI.A677697 CONTENTS CHAPTEB PAeX I. Tom Takes Up Radio 1 II. Mysterious Messages 16 III. The Radio Detectives 36 IV. The Boys Draw a Blank 57 V. The Under-sea Wireless 82 VI. The Red Menace 98 VII. The Cry from the Depths . . . .121 VIII. Astounding Discoveries 139 IX. The Battle beneath the River . . .158 X. Radio Wins 177 XI. Henderson Has an Interview .... 194 XII. The Confession 211 XIII. Rawlins' Proposal 230 T THE RADIO DETECTIVES CHAPTER I TOM TAKES UP RADIO OH, Dad! I've made a new set," cried Tom, as he entered the dining room. "That so. Son?" replied Mr. Pauling interestedly. "Seems to me you boys do nothing but junk your sets as fast as you make them and build others. Does this one work better than the last?" "It's a peacherino!" declared Tom enthusiasti- cally. "Just wait till you see it and listen to the music coming in." "I'll come up after dinner," his father assured him. "Let me know when the fun begins. I'vei some papers to go over in the library first." Throughout the meal the talk was all of radio, in which Tom and his boy friends had become madly interested and in which Tom's father and mother had encouraged him. "Go to it, Tom," his father had said when the 1 THE RADIO DETECTIVES boy had glowingly expatiated on the wonderful things he had heard on a friend's instrument and had asked his father's permission to get a set. "I'm glad you're interested in it," he had con- tinued. "It's going to he a big thing in the future and the more you learn about it the better. But begin at the beginning, Tom. Don't be satisfied merely with buying instruments and using them. Learn the whole thing from the bottom up and use your mechanical ability to build instruments and to make improvements. Wish they'd had some- thing as fascinating when I was a kid." Tom had lost no time in availing himself of his father's permission, and of the roll of bills which had accompanied it, and there was no prouder or more excited boy in Greater New York than Tom Pauling when he triumphantly brought home his little crystal receiving set and exhibited it to his parents. "I can't understand how a little box with a few nickel-plated screws and some knobs can do all the things you say," was his mother's comment. "But then," she added, "I never could understand anything mechanical or electrical. Even a phono- 2 TOM TAKES UP RADIO graph or an electric light is all a mystery to me." Mr. Pauling looked the instrument over care- fully and listened attentively to Tom's graphic ex- planation of detectors, tuners, condensers, etc. "H-m-m," he remarked, "I guess I'll have to take a back seat now. Son. You evidently have a pretty good grip on the fundamentals. Sorry I can't help you any, but it's all Greek to me, I ad- mit." "Oh, it's all mighty simple," Tom assured him. "Frank's coming over this afternoon and we're go- ing to put up the aerial and then you and mother can hear the music and songs from Newark to- night." But despite the fact that Mrs. Pauling declared it the most remarkable thing she had ever seen or heard, and his father complimented him, Tom was far from satisfied with his first set. He didn't like the idea of being obliged to sit with head phones clamped to his ears in order to hear the music from the big broadcasting stations; he felt that it was mighty unsatisfactory for only one per- son to hear the sounds at one time and he soon found that despite every effort he was continually 3 THE RADIO DETECTIVES interrupted by calls and messages from near-by amateur stations. Being of a naturally inventive and mechanical mind and remembering his father's advice to try to improve matters, he spent all his spare time studying the radio magazines, haunting the stores where radio supplies and instruments were sold and arguing about and discussing various devices and sets with his boy friends. Hardly a day passed that he did not arrive at his home carrying some mysterious package or bundle. Accom- panied by his chum Frank, from the time school was over until late in the evening he kept himself secluded in his den while faint sounds of hammer- ing or of animated conversation might have been heard within. "What's all the mystery, Son?" his father had asked on one occasion. "Going to spring some big invention on an unsuspecting world?" Tom laughed. "Not quite. Dad," he replied, "but I'm going to give you and mother a surprise pretty soon." When at last all was ready and his parents were invited to Tom's holy of holies they were indeed 4 TOM TAKES UP RADIO surprised. Upon a small table were various in- struments and devices and a seeming tangle of wires, while, tucked away on a bookshelf, was the little crystal set which had so recently been Tom's pride and joy. And still greater was their surprise when, after busying himself over the instruments, the faint sounds of music filled the room, coming mysteri- ously from the apparent odds and ends upon the table. "It's all homemade," Tom had explained proudly. "But it works. Frank and I rigged it up just as an experiment. Now I'm going to re- assemble it and put it in a case and have a regular set." "Wait a minute, Tom," his father had inter- rupted. "You'll have to explain a bit. If that lot of stuff can give so much better results than the set you bought, why didn't you make it in the first place, and what's the difference anyway?" "Well, you see. Dad," Tom tried to explain, "I had to start at the bottom as you said and a crys- tal set's the bottom. This is a vacuum tube set. Those things like little electric lights are the tubes 5 THE RADIO DETECTIVES and they're the heart of the whole thing, and I've a one-step amplifier and that has to have another tube. I didn't have enough pocket money to buy everything so Frank lent me some of his. You see it's this way " "Never mind about the technicalities," laughed his father. "As I said before, go to it. Get what you need and keep busy. It's a fine thing for you boys. Now turn her on again, or whatever you call it, and let's hear some more music." From that time, Tom's progress was rapid al- though, as his father had jokingly remarked, the boy's chief occupation appeared to be building sets one day only to tear them down and recon- struct them the next. Tom's room had assumed the appearance of an electrical supply shop. Tools, wire, sheet brass, bakelite, hard rubber knobs, odds and ends of metal, coils and countless other things had taken the places of books, skates, baseball bats and papers, and the fiction magazines had given way to radio periodicals, blue prints and diagrams. Mrs. Pauling was in despair and complained U her husband that Tom was making a dreadful mess 6 TOM TAKES UP RADIO of his room and expressed fears that he might get hurt fooling with electricity. "Don't you fret over that," her husband had advised. "Tom and his friends are having the time of their lives. As long as they are learning something of value, what does it matter if they do keep his room in a mess? Besides, it's clean dirt you know — and it's orderly disorder if you know what I mean. They're exploring a new world and haven't time to look after such trifles as having a place for everything and everything in its place. That will come later. Just now they are fired with the zeal and enthusiasm of great in- ventors and scientists. We mustn't interfere with them — such feelings come to human beings but once in a lifetime. I consider this radio craze the best thing for boys that ever occurred. It gives them an interest, it's educational, it keeps them oflf the street and occupies their brains and hands at the same time. Do you know, if I didn't have my time so fully occupied, I believe I'd get bitten by the bug myself. Besides, they may really dis- cover something worth while. I was talking to Henderson of our staff to-day — he had charge of 7 THE RADIO DETECTIVES our radio work during the war — and he tells me some of the best inventions in radio have been made by amateurs — quite by accident too. I ex- pect Tom knows that and that's what makes the kids so keen on the subject — it's a wonderful thought to feel you may stumble on some little thing that will revolutionize a great science at any moment." "Yes, I suppose you're right, Fred," agreed Tom's mother resignedly. "But I do wish it were possible to have boys amuse themselves without tracking shavings all over the halls and burning holes in their clothes and having grimy fingers." But Tom's mother need not have worried. "Gradually order came out of chaos. As the boys progressed, they found that the accumula- tion of odds and ends and the disorder in- terfered with their work; many experimental in- struments and devices had been discarded and were now tossed into a junk box in the closet; a neat work table with the tools handily arranged had been rigged up and Tom and Frank had developed a well-equipped and orderly little workshop with the completed instruments on an improvised bench under the window. 8 TOM TAKES UP RADIO Both Mr. and Mrs. Pauling had noticed the grad- ual improvement, as from time to time they had been summoned by Tom to witness demonstrations of the latest products of the boys' brains and hands, and both parents congratulated the boys on their handiwork and the strides they had made. So, on the night when Tom had assured his father that his latest set was a "peacherino," the two grown- ups entered a room which, as Mr. Pauling ex- pressed it, reminded him of a wireless on a ship. And then, after Tom with the glowing eyes and flushed face of an inventor and the pride of a show- man, had exhibited his latest achievement and had explained its mysteries in terms which were utterly unintelligible to his parents, they sat spellbound as the strains of a military band fairly filled the room. "Fine!" declared Mr. Pauling when the concert ended. "You have got a *peacherino' as you call it." *'0h, that's nothing," declared Tom deprecat- ingly. "I can get Pittsburgh and I can get spark messages from Cuba and Canada, and last night I 9 V THE RADIO DETECTIVES picked up a message from Balboa. I'll hear Eng- land and France before I'm satisfied." "Bully!" exclaimed his father. "Tell you what I'll do. I'm oflf to Cuba and the Bahamas, Mon- day, you know. I'll radio from the ship on the way down and after I get there you can see if you can pick up my messages direct and can talk back." "Oh, I can't do that, yet," declared Tom. "I haven't a sending set. You have to get a license for that, but I'm going to get at it right away. It will be fine to be able to hear you. I'll bet I can get your messages from Cuba and Nassau. Say, it will be almost like hearing you talk." "How shall I address them?" chuckled his father. "Tom Pauling, The Air?" "Gee! I hadn't thought of that," ejaculated Tom. "I haven't any call letters — only sending stations have them — I've got it! When you send a message, just address it as if it were a regular message and then I'll know it's for me. And send them the same time every time — ^then I'll be sure to be here and waiting to get them." "Righto," agreed his father. "I'll be sending a good many official messages, I expect, and I can 10 TOM TAKES UP RADIO get them all off together each day — say 7:45. How will that be?" "That'll be fine," assented Tom. "I'll be here at half-past seven every night listening. Say, Dad, do you suppose those smuggler fellows use radio?" "Why, I don't know; what made you ask?" "Oh, I just happened to think of it," replied Tom. "I guess your speaking of sending official messages and starting for Cuba and the Bahamas just put it in my head." "Well, if we don't find how they're getting liquor into the States by wholesale pretty quick, I'll begin to think they're sending the booze in by radio," laughed Mr. Pauling. "It's the most mysterious thing we've been up against yet. Can't get a clue. Perhaps they are using radio to warn one another, or maybe they're onto our -codes. Suppose you keep track of any odd messages you hear, Tom. I don't suppose there's anything in it, but it will give you another interest and one never knows what may happen through chance or accident. Remember that coup I told you about that we made during the war — that meaningless message that 11 THE RADIO DETECTIVES passed all the censors and that, by pure accident, led to the capture of the worst lot of German plotters in the country?" But Frank had not heard the story and so, from radio, the conversation drifted to Mr. Pauling's ex- periences as an ofl&cer of the Department of Justice during the war and from that to his present prob- lem of tracing to its source the mysterious influx of liquor which was flooding New York and other ports despite every eff'ort of the government to stop it. It was on this work that he was leaving for the West Indies, and long after he and Mrs. Pauling had left the room, Tom and Frank remained, talk- ing earnestly, and with boyish imagination dis- cussing the possibilities of aiding the government through picking up some stray information from the air by means of their instruments. "We ought to have better sets," declared Tom. "These are all right for getting the broadcasted entertainments and spark signals, but we can't get the long waves from the big stations. And we don't always get farther than Arlington or Pitts- burgh with this. Last night, we heard Balboa, but 12 TOM TAKES UP RADIO the night before that we couldn't get Havana. If we're going to hear Dad from Nassau or Cuba we want a set we can depend upon." "I'll tell you what we'll do," replied Frank. "Let's put everything that we both have together and have a fine set here in your room. I'll bring my stuff down and we can work together — have duplicate sets and everything — and I'll just keep that little old set of mine so I can use it when I happen to be home." "That's a good idea," agreed Tom, "Dad's so in- terested in our work I can spend a lot more money on instruments and he won't mind and school will soon be over and we can devote all our time to it. Gosh, I bet we have the best sets of any boys in the whole of New York! Say, won't it be great when we can hear messages from England and Germany and France?" "Yes, and we want to get busy on a sending set too. It's twice as much fun when we can talk to others as well as hear them. And say! my folks are going to Europe next month. If your mother and father don't mind I could stay here with you." '^That's bully! Of course mother won't mind 13 THE RADIO DETECTIVES and Dad will be glad to have you," declared Tom. "We're not going any place this summer and so we can give all our vacation to radio. Say, we may make some big discovery or invention. I was reading the other day about how many things there are to be done in radio yet and the fellow that wrote it said he believed some of the big things would be discovered by boys or beginners accidentally." Mrs. Pauling was very glad to have Frank plan to stay with Tom while his parents were absent and for several days the two boys were busy pack- ing up Frank's radio outfits and carrying them to Tom's house. When at last everything was there the boys had a veritable treasure trove of materials, for Frank had not been stinted in the amount he could spend on good tools, supplies and instruments and, while he did not possess the mechanical or inventive abil- ity of Tom, yet he wag a very careful and painstak- ing worker and everything he had was of the best. Tom, on the other hand, preferred to make everything himself and, although his father was willing to let him have any sum within reason to 14 TOM TAKES UP RADIO carry on his radio work, he spent most of the money for tools and supplies and had built a number of special instruments which even Frank admitted were big improvements over ready-made devices. In addition, he had a very complete library of radio books as well as scrapbooks filled with clip- pings from the radio columns of the various news- papers and periodicals. Hence the two boys made most excellent partners for carrying on their ex- periments and building their sets. Fortunately, too, they were not the type of boys who soon be- come tired of a subject and take up one fad after another and, while they were both strong, red- blooded, out-of-door boys, always ready for the most strenuous games, long hikes or hunting and fishing, they found radio so much more fascina- ting than football, baseball or other sports that practically everything else had been abandoned. CHAPTER II MYSTERIOUS MESSAGES FOR the next few days the boys were very busy perfecting^ their instruments and, when Mr. Pauling bade Tom and his mother good-by and sailed southward, Tom as- sured him that he would be able to pick up any messages he sent. "Maybe I'll surprise you by sending a message," he declared. "I'm going to apply for a license next week and make a sending set. Of course it won't be able to send clear to Cuba or Nassau, but freak messages do go long* distances sometimes and any- way, I can get in* touch with your ship before you reach port coming back." "Great!" exclaimed his father heartily. "And don't forget about stray messages — ^you may help us out yet. I spoke to Henderson about your idea that the bootleggers were using radio and he says he should not be a bit surprised. They're right up to date in their methods, you know." 16 MYSTERIOUS MESSAGES That evening, Tom and Frank hurried to their sets promptly at 7:30 accompanied by Mrs. Paul- ing who seemed as interested as the boys in the re- sult of their first attempt to pick up a message in- tended for them. She was rather disappointed, however, when Tom clamped on his phones and told her she wouldn't be able to hear anything. "You see," he explained, "if the message comes in, it will be just code signal — dots and dashes in International Morse — and wouldn't mean anything to you and I might miss it if I used the loud speaker." Slowly the minutes slipped by. From out of the silent air came various sounds to the boys' im- patient ears — little buzzing dots and dashes from local stations; the faint sounds of a phonograph from some amateur's radiophone; fragments of speech from a broadcasting station. Carefully the two waiting, expectant boys tuned their instru- ments, for they had taken the precaution of asking the wireless operator on the ship what wave length he used and with their sets tuned as nearly to this as possible they cut out the amateur senders with their short wave lengths and the broadcasting 17 THE RADIO DETECTIVES stations with their evening entertainments on 360 meter waves and heard only the meaningless or un- interesting Morse messages passing from ships to shore or vice versa. Over and over Tom and Frank glanced anxiously at the little nickel-plated clock ticking merrily on its shelf, until at last the hands pointed to 7:45 and the boys fairly thrilled with excitement. Would they hear the message from the speeding ship? Would they pick up that one message that they were expecting? Would they, in a moment more, be listening to the dots and dashes that represented Mr. Pauling's words? Neither boy was yet ex- pert at reading Morse if sent rapidly, but the wire- less man aboard the Havcaia had laughingly agreed to send Mr. Pauling's messages slowly and the boys were not worried on that score. Suddenly, to Tom's ears, came a sharp buzz — faint and blurred, and with trembling fingers he tuned his set, adjusted the variable condenser and as the short, staccato sounds grew sharp, loud and clear he knew that the long-hoped-for message was coming to his ears. "Dah, dab dah dab, dab dah, dee dah dah dee, dee dah, dee dee dah, dee dah 18 MYSTERIOUS MESSAGES dee dee, dee dee, dah dee, dah dah dee," came the dots and dashes, sent slowly as if by an ama- teur and mentally Tom translated them. Yes, there was no doubt of it, TOM PAULING were the words the dots and dashes spelled and Tom's heart beat a trifle faster and his face flushed with excitement as he heard his own name coming out of space and realized that, across a hundred miles and more of tossing sea, his father was talk- ing to him and steadily he jotted down the letters as they buzzed in dots and dashes through the air from the distant ship. "Hurrah!" he fairly yelled, as with the final "dee dah dee dah dee" the operator signified that the message was finished. "Hurrah! I got it. See, here 'tis. Mother!" Frank also had received the message on his set and the two compared the letters they had written down. "Of course we made some mistakes," explained Tom as his mother puzzled over the unpunctuated, apparently meaningless letters. "See," he con- tinued, "you have to separate the letters into words and sentences and this one should be an "N" in- 19 THE RADIO DETECTIVES stead of an "A" and I guess this is a "D" instead of a "B," Frank's got it that way. One's a dash and three dots and the other's a dash and two dots." As he spoke, Tom was busily copying the let- ters and forming words and presently showed his mother the finished message. "That's it," he an- nounced proudly. "Just think of Dad talking to us — and he'll do it every night all the way down and after he gets there. Gosh! It's funny to think we can hear from him that way. Say, isn't radio great?" "But I thought you could hear him talking," said his mother in rather disappointed tones. "He could send messages that way by the regular radio companies or by cable." "Of course he could," agreed Tom somewhat disturbed because his mother was not more enthu- siastic over his achievement. "But you see the fun is in getting it ourselves this way. It wouldn't be any sport to have the messages brought in an envelope like ordinary telegrams. Gee! I just wish we could hear him talk over the phones. Some of the ships have talked with the shore far- 20 MYSTERIOUS MESSAGES ther away than he is, but I guess the Havana* s radio isn't up-to-date." "I think it's fine and splendid of you boys to be able to do this," declared his mother. "What I meant was, that I had expected to hear your father's voice and I really was disappointed when I found it was so different." "Well, I'm going to fix a set to talk back to him," said Tom. "And just as soon as I get the sending set done we'll get to work and make a better re- ceiving set, won't we, Frank?" "You bet!" agreed Frank. "Perhaps by the time your father is on the way back we can really talk to him." "Now let's have some music," suggested Tom, and for the next hour they all listened to the broad- casting station's program as the loud speaker filled the room with the sounds of music, singing, speeches and news. For the next three nights the two boys picked up Mr. Pauling's messages regularly and were as proud as peacocks when they managed to get the first message from Havana telling of his safe arrival in Cuba. And by their enthusiastic studies 21 THE RADIO DETECTIVES and the practice they gained by deciphering the messages, the boys were successful in passing the required examination and proudly exhibited their license to maintain and operate a sending station. - It was a red letter day in their lives when they at last had the transmitting set in working order and flashed a message into the night, to have it promptly answered by an unknown boy in Garden City. Each night, too, they sent out messages di- rected to their father in the vain hope that, by some chance or by the same mysterious combina- tion of conditions which had wafted other mes- sages to vast distances beyond the range of the in- struments, their words might be picked up in Havana or Nassau; but no reply came and at last they gave up in despair. Then, their sending set being no longer a nov- elty, the boys set diligently to work on other mat- ters and worked early and late. "What on earth is that?" asked Tom's mother, when finally the new idea had assumed concrete form and she was invited to witness a demonstra- tion. "It looks like some sort of a huge bird- cage," she continued as she seated herself and 22 MYSTERIOUS MESSAGES glanced at the wooden framework wound with wire that stood on a small table. "Well, I don't suppose you can understand," replied Tom, with the superior air of one who is master of an art beyond ordinary comprehension, "but ril try to explain. That's a loop aerial." "But I thought the aerial was that wire clothes- line-like affair on the roof," objected Mrs. Paul- ing. "You see," she laughed, "I am beginning to learn a little." Tom grinned. "Oh, yes, that's an aerial, too," he replied. "But this is another kind. With this we don't need any ground or lead-ins or light- ning switches. And it's directional too. That is," he hastened to explain, "by turning it one way or another we can pick up signals from certain directions and not from others. Some people call them compass aerials and they're used on ships for locating other vessels or for finding their way. And besides, they cut out a lot of static." "Now please, Tom, what is all this you're talk- ing about? What is static?" "Well that's mighty hard to explain," said Tom, scratching his head reflectively. "It's a sort of 23 THE RADIO DETECTIVES electricity in the air — lots of it around when there are thunderstorms and lightning." "Lightning!" exclaimed his mother. "Do be careful, fooling with all these things, Tom. I'm always afraid you'U get a fearful shock or some- thing." "Nonsense," laughed Tom. "Static doesn't hurt any one and lightning won't do any harm. An aerial is just like a lightning-rod and if it's struck the lightning is just carried down to the ground harmlessly; but this loop aerial's different. Now let's hear how it works." Adjusting the instrimients and attaching the loud-speaker, Tom slowly turned the cagelike affair about and suddenly, as it faced the west, the sounds of music burst out from the horn. "There 'tis!" cried Tom, exultantly. "That's Newark. Now, see here." As he spoke, he swung the loop aerial to one side, and instantly, the music died out. "Now, listen carefully," he continued and turned the loop slowly around until, somewhat fainter, the sounds of a human voice came from the loud-speaker. "That's Pitts- burgh," declared Tom. "Now you see how it 24 MYSTERIOUS MESSAGES works. If it's turned towards Newark we get Newark and if towards Pittsburgh we get that.'* "Yes, it's all very interesting," admitted his mother. "But what advantage is it? You used to hear both Newark and Pittsburgh with the aerial on the roof." "Oh, it's no advantage for ordinary work," re- plied Tom. "But it's a fine thing in some ways. Now, for instance, if we heard a fellow's message and didn't know where it came from we could tell by turning this back and forth until we got his direction. Then, if we wanted to locate him ex- actly, we could put it up somewhere else and in that way we could find out just where he was. Frank and I have a particular scheme in hand, but that's a secret and I'm not ready to tell it yet." His mother laughed. "I'm not a bit curious," she declared. "I suppose some day I'll wake up to find you two boys have astonished the world." But had Frank and Tom told Mrs. Pauling what their secret was she would have been both curious and surprised. Several times within the preced- ing weeks the boys, listening at their instruments, 25 THE RADIO DETECTIVES had received messages which they could not locate. At first they had given no heed to these, thinking they were merely from some amateur, but when, after repeated requests for the unknown's call let- ters, no answer was received and the messages abruptly ceased, the two boys began to be cur- ious. "There's something mighty funny about him," declared Frank. "Every time we answer him or ask a question he shuts up like a clam. Say, Tom, maybe he's a crook or a bootlegger." "More likely some amateur sending without a license and afraid the government inspector will get after him," suggested Tom. "But I would like to find out who it is." A few days later Frank, who was poring over the latest issue of a radio magazine, uttered an exclamation. "Gosh! here's the scheme," he cried. "Now we can find out who that mysteri- ous, chap is." "What's the big idea?" queried Tom, who was busy making a new vario-coupler. "Loop aerial," replied his chum. "Here's an article all about it. It says they're used aboard 26 MYSTERIOUS MESSAGES ships to find the location of other vessels and are called compass aerials." Tom dropped his work and hurried to Frank's side. "Well," he remarked, after a few moments' study of the article and the diagrams, "I don't see how that would work in our case. It says one ship can find another or can work its way into port by using the loop aerial like a compass, but the trouble is the ship's moving and so the thing will work, but we can't go running around New York City or the state with a set in one hand and a big loop aerial in the other." "No," admitted Frank rather regretfully, "but we can tell in which direction his station is." "Yes, and it will be fun to make one and experi- ment with it," agreed Tom, "especially as the ar- ticle says the thing cuts out static and interfer- ences and it's getting on towards warm weather now when the air will be full of static." "Well, let's make one then," suggested Frank. As a result, the boys had constructed their loop aerial and a special set to go with it and the very first time they tested the odd affair they were over- 27 THE RADIO DETECTIVES joyed at the result. Again they had picked up the messages which had aroused their curiosity and, by turning the loop one way and then another, they were soon convinced that the sender had a station to the southeast of their own. "Well, that's settled," announced Tom, "and the only things southeast of here are the East side, the river and Brooklyn. That fellow is not far away — he's using a very short wave and his messages are strong. I'll bet he's right here in New York." "I guess you're right," agreed Frank, "but that doesn't do much good. There's an awful lot of the city southeast from here." "Sure there is," said Tom, "but, after all, what do we care. I still think he's just some unlicensed chap — probably some kid over on the East Side who can't pass an examination or get a license and is just having a little fun on the quiet." This conversation took place two days before Tom received his father's message telling of his safe arrival in Cuba and no more messages from "the mysterious stranger were heard until the day after Mr. Pauling's message had been received. Then, as Tom was listening at the loop aerial 28 MYSTERIOUS MESSAGES set and idly turned the aerial about, he again picked up the well-known short-wave messages. Heretofore the messages had been meaningless sentences in code, dots and dashes which the boys out of curiosity had jotted down only to find them devoid of any interest — items regarding shipping which Tom had declared had been culled from the daily shipping lists and were being sent merely for practice — and so now, from mere habit, Tom wrote down the letters as they came to him over the instruments. Suddenly he uttered a surprised whistle. "Gee Whittaker!" he exclaimed in low tones. "Come here, Frank." The other hurried to him and as he glanced at the pad on the table beside Tom he too gave an ejaculation of surprise. The letters which Tom had jotted down were as follows: LEAR P IN HAVANA ARRIVED YESTERDAY GET BUSY. "They are rum runners!" cried Tom as the sig- nals ceased. "Gosh, I believe they are!" agreed Frank. "But of course," he added, "it may not mean your father by T' and we don't know the first part of 29 THE RADIO DETECTIVES the message. Maybe they were just talking about a ship — that 'lear' might have been something about a ship clearing for some place." "You are a funny one," declared Tom. "Here you've been insisting all along that there was some deep mystery or plot behind these messages and I've said it was just some amateur and nothing to it and now, just as soon as we get a message which really means something, you shift around and say it's only about some boat." "Well, if it's anything secret why do they talk plain English?" asked Frank. "That's what makes me change my views. When they were sending things that sounded like nonsense I thought they might be code messages, but now that they send things that are so plain it doesn't seem mysterious." "Yes, there's sense in that argument, I admit," replied Tom. "But perhaps there was just as much sense in the others — if they are bootleggers. Of course as you say, they may not mean anything about Dad, but it would be a mighty funny coinci- dence if any one or anything else beginning with 'P' arrived in Havana yesterday and it happened 30 MYSTERIOUS MESSAGES to come in with this message and with a 'get busy' after it. I'll bet you, Frank, they're smugglers and that's a message to some boat or something that the coast's clear and to unload their stuff. Let's go down and tell Mr. Henderson about it." "No," Frank advised. "He'd probably laugh at us and it wouldn't be any use to him anyhow. We'll keep the message and all others we hear and if anything else is going on we'll get some more messages, you can bet. And I've a scheme, Tom. I know a fellow down at Gramercy Park and we can go down there and set up a loop aerial and see if this chap that's talking is still southeast of there." "That's a bully scheme!" cried Tom with enthusiasm. "We can turn radio detectives — that'll be great! And if we find he's north or west or east of Gramercy Square we can try some other place. Probably your friend knows fellows who have sets all around that part of the city." The next day they visited Frank's friend and after making him promise secrecy they divulged a part of their plan, omitting, at Tom's suggestion, any reference to their suspicions of the messages 31 THE RADIO DETECTIVES coming from a gang of bootleggers. Henry fell in readily with the idea of locating the messages, which he had also heard repeatedly, and was deeply interested in the loop aerial. He had an excellent set and numerous instruments and sup- plies and the three boys soon rigged up a compass set in Henry's home. "Now, you listen with this and try to pick him up," instructed Frank. "Keep turning the aerial about in this way and, as soon as you hear him, write down what he says. We'll listen too, when- ever we have a chance, and will let you know. Then, if you haven't picked him up, you can turn the loop until you do. Too bad you haven't a sending set so you could tell us." "But he'll hear you and quit," objected Henry, '*and how can I hear you if I don't happen to have the loop pointed your way or am listening to this fellow?" Frank looked puzzled. "Gee!" he ejaculated, "I hadn't thought of that. "Oh, that's easy," declared Tom. "You'll hear us over the other set with the loud-speaker you have. That works with a regular aerial and is 32 MYSTERIOUS MESSAGES entirely separate from this set. And we'll arrange a code so he won't know what we're talking about. Let's see, I guess we'd better use the phone and not send dot and dash, we'll just say 'we've got the message' and you'll know what it means." "No, that's no good," declared Frank. "That's not a bit mysterious or exciting. We're radio de- tectives, you know. We must have something like a password or code or something. Say, let's begin with 'loop', then Henry'll know we mean him. We'll say 'loop, be ready to receive.' " **Yes, and have him know something's wrong when we don't begin to send anything," said Tom. "I have it!" exclaimed Henry. "Say, 'loop, com- ing over,' and then any one'll think you are tell- ing me you are coming over here. But say, how'll I get your message if I don't sit at my set and tune to you?" "That's easy," said Frank. "Just as soon as we get home to Tom's we'll begin to send and you listen and tune until you get us good and loud and then mark your knobs so you can set 'em when- ever you want to hear us. Then ring us by regular phone and tell us it's 0. K." 33 THE RADIO DETECTIVES Thus, all being arranged, Tom and Frank went up town and as soon as they reached Tom's room began to send calls for Henry as they had agreed. Very soon the telephone bell rang and Tom ran to the instrument. "It's all right, Frank," he announced as he re- turned to the room. "Henry says he got our calls finely and has marked his knobs. He's going to turn them about and then set them back at the marks and we're to call him again. Then if he gets us right off he'll know he won't miss us next time." When, a few minuts later, the phone rang again and Henry told Tom that the message had come in on the adjusted set the boys felt sure that their fellow conspirator would not miss any calls they might send him. So, having nothing else to do, they worked at another step of amplification for their new set, and listened for any signals or mes- sages that might come in from the person whom they were endeavoring to trail by means of radio. Evidently, however, the mysterious stranger had no business to transact and no message from him was received. When at last they were obliged to 34 MYSTERIOUS MESSAGES leave for dinner they phoned to Henry who re- ported that he had been listening all the after- noon, but had heard nothing. "We'll get at it again to-night," said Tom. "Most of the messages we've heard come in just when the broadcasting stations are giving their concerts. I'd bet he takes that time so nobody will hear him, or pay attention to him. If they're all tuned to 360 meters they'd never know he was talking, you see, and if they just chanced to hear him they'd be too busy with the music to bother with him." As Tom had suspected, the mysterious mes- sages did come in that night and so interesting and exciting did they prove to the boys' imaginative and suspicious minds that they were thankful they had foregone the pleasure of hearing the con- cert on the chance of the supposed smugglers talking. CHAPTER III THE RADIO DETECTIVES THE instant the boys recognized the long- awaited signals, Frank called Henry and notified him as agreed and, to their delight and satisfaction, the mysterious stranger continued to talk, evidently paying no heed to the seemingly innocent words of the boys, if indeed he had heard them. As heretofore, much that was said meant noth- ing to the boys, but wisely they jotted every thing down nevertheless. However, both Tom and Frank were more puzzled than ever, for now that their minds were concentrated on the messages they suddenly realized that a true conversation, an in- terchange of messages, was going on, but, for some inexplicable reason, they could hear but one of the speakers. It was like listening to one individual talking to another over an ordinary tele- phone and the boys could merely guess at the words of the inaudible speaker. 