Radio Detector Development by H. Winfield Secor, A.I.R.E.
While wireless telegraphy is a far cry from the philosophy and traditions of the Hindus, it may not be inopportune to cite, for purposes of comparison, an ancient tradition of the Hindu priests which brings out in a marked and comprehensible manner the gigantic loss existing in wireless telegraphic transmission, with especial regard to the infinitesimal amount of energy that is received at the wireless receiving station with which to actuate the detector.
The Hindus, with all their profound philosophical deductions, were never able to figure out the age of the earth any more definitely than our geologists and scientists have to-day. But they did have a very good example by which to live a practical idea as to this vast stretch of time. Said they:
让我们假设我们有一个大理石立方体1英里x1 mile wide and 1 mile long. Suppose, also, that a lady wearing a shawl visits this marble cube once in every hundred years (presumably not the same lady), and that she brushes the marble once with her shawl. In time, of course, the marble will be worn down to the size of a pea, and he who can figure out the length of time in years required for this to be accomplished, would know the age of the earth. And the Hindus called this period of time one Marcalper, and the actual age of our planet as one Marcalper times one Marcalper.
This is a homely little story which may help by comparison to instill in the lay mind something of the enormous loss of energy which takes place in the transmission of Radio signals over great distances.
We will not deal exhaustively, or even attempt to, in the present discussion, on the efficiency of wireless transmission for any given condition or set of conditions, but an example of the amount of energy utilized at a typical trans-oceanic or trans-continental radio station and that arriving at the receiving station may be illuminating.
我们很容易假设功率x射线检验的数量ated at a transmitting station for a 3,000 or 4,000 mile range is 50 K.W. or 50,000 watts. Bearing in mind that a watt is equal to 1 volt times 1 ampere, and that it is considered excellent when 20 micro-amperes or about .01 micro-watt is registered at the receiving station with which to actuate the detector, then we have some idea as to how all-important the radio detector is and we have an analogy to a degree, with the Hindoo philosophy cited above. With 50 K.W. used at the radio transmitter and but .01 microwatt received, we find that this is but onefive-trillionth（L / 5,000,000,000,000,000,000,000）的能量发出。在留下这一点之前，请提及10个微安培（1个微安培（1微米等于Ampere的一个单Mi1lion），被认为是一个弱信号，20微安培接收电流强的信号。从技术上讲，无线电探测器通常被电能的量评级ergsnecessary to actuate them.
One of the first, and, so far as we know, really the first wireless detector which would manifest and interpret the electro-magnetic waves sent thru the ether by a spark discharge such as that from a static machine or induction coil, is theHertz Micrometer Spark GaporResonator, shown at Fig. 1.
This comprised simply an insulated handle on which was mounted a flexible metal loop and the abutting ends of which carried spark points or balls, which could be separated or brought very close together by a fine micrometer screw attachment as shown. For short distances such as in laboratory tests over a few hundred feet, the spark gap resonator proved successful and showed Heinrich Hertz the way to his important deductions on which is based to a very large extent the wireless telegraph that we know today. The gap is regulated when in use until tiny sparks are seen to pass between the points every time the transmitting key is depressed.
Next we come to theFilings Cohereras used by Guglielmo Marconi in the first commercial radio sets which he built and installed on a number of vessels. The coherer is shown at Fig. 2 with its magnetic taper, resembling a vibrating type electric bell, which, having its circuit closed by the relay connected with the coherer, served to shake the glass coherer tube and the metal filings within it and to de-cohere the filings or shake them apart. The coherer was then ready for the next signal.
某些金属屑和精确的比例as found by lengthy experiments (after the method of Professor E. Branly of France) are placed within the evacuated glass tube as shown. This is carried on an ivory rod. Normally, and before the arrival of a wireless impulse from the transmitting station, the filings lie loosely in the tube and the resistance of the coherer is very high, causing the relay to remain neutral. When a wireless signal arrives, the current induced in the antenna passes thru the coherer to earth and causes the minute metal filings (usually a mixture of nickel and silver) to “cohere” or stick together. This has the effect of lowering the resistance of the coherer quite markedly and permits sufficient battery current to pass thru it and thus close the relay armature.
同时脱孔或锥形电路关闭，并且在Marconi开发的这种类型的最终无线电接收组中，Morse卷筒记录器也连接在电路中，记录了输入点和破折号，然后操作者可以破译它们休闲中。此外，在这种情况下收到的每条信息都有一个永久记录，这通常是至关重要的，特别是在军事和海军工作中。然而，同性恋者在几种缺陷中，它不是很敏感，并且难以调节。它经常在许多情况下进行调整，在其调节或设置后一两分钟。
Referring to Fig. 3, we have what is known as theAuto-Coherer。Several types of this detector have been evolved, but are practically extinct nowadays, owing to lack of sensitivity and other untoward features. One of the principal auto coherers developed was that known as theCastellicoherer and is said to have been used at one time by the Italian navy. It employed one or more globules of mercury within a glass tube, this globule (of 1.5 to 3 m.m. diameter) being placed between iron and (polished surface) carbon electrodes, preferably, as shown in the illustration. A modification of this arrangement, first used by Mr. H. Gernsback, involved the substitution of polished carbon granules between an iron and carbon electrode. These detectors were used with a telephone receiver and battery (one dry cell). They possess the faculty of establishing decoherence automatically, and thus are always ready to receive the next signal upon the cessation of the previous one. Their resistance falls upon receipt of a signal.
The detector illustrated at Fig. 4 is the well-known Rutherford-Marconi磁探测器。This instrument operates on a very unique principle, viz., that of the reduction in any hysteresis effect occurring in an iron core, when this core is subjected to the effect of a Hertzian wave current passing thru the receiving circuit, according to the researches of C. Maurain. The complete detector is so arranged that a band of fine insulated iron wires constantly revolve about two rotary drums, driven by a spring or electric motor, and a pronounced hysteresis or magnetic frictional effect is produced in that section of the traveling iron wire band directly under the poles of a set of steel magnets mounted as shown. At this point there is also placed a small transformer containing a primary and secondary coil. Thru the primary coil is past the aerial current induced by the incoming electro-magnetic wave, while to the secondary coil is connected a pair of low resistance telephone receivers.
It is evident, from the foregoing explanation, that at every incoming signal there will be a sound heard in the ‘phones as the Hertzian wave currents flowing around the primary coil cause partial cessations or reductions in the hysteresis effect produced in the moving iron wire band.
The铅的过氧化物detector devised by S. G. Brown of England is illustrated at Fig. 5. This detector has proven quite successful and is used with a pair of sensitive telephone receivers and a critically adjusted battery current. The instrument comprises a peroxid of lead pellet mounted between an upperleaddisk and a lowerplatinumone; the pressure on the peroxid of lead pellet being adjustable by means of a thumb screw and spring in the usual fashion. This detector has been termed, more or less correctly, thedryelectrolytic detector and its action is supposed to depend upon the fact that an incoming oscillation intensifies the counter-electromotive force set up by the cell (electro-chemical action due to lead-peroxid lead-platinum couple) and which opposes the applied battery current (1.5 volts about), thus causing the detector to increase its effective resistance. This results in a drop of current in the ‘phone circuit; as soon as the oscillation ceases the ‘phone current increases.
The裸点电解探测器illustrated at Fig. 6 has been the subject of much discussion among radio men as to who really was the basic inventor of it. But most writers of the day give credit, jointly, to Dr. Michael I. Pupin (1899), Professor Reginald A. Fessenden (1903) and W. Schloemilch (1903).
该探测器的作用基于以下事实：如果允许在直径少千分之一的英寸的极细铂金属焊丝将其部分浸入酸性溶液中（例如由五个零件水组成的颗粒）部分地浸入其末端一种部分硝酸），即进入的赫兹波电流将倾向于捕捉到围绕细铂金属线的强偏振（产生精细气泡的产生），这通常使电池电路中的阳极成为阳极。Further, the electrolytic detector has been found by Professor G. W. Pierce to act as a rectifier and that the inherent action is also based on polarization capacity at the electrodes as first described by Pupin in 1899. Dr. L. W. Austin and others have found that the fine platinum wire may be positive or negative for feeble oscillations with equal results. The acid solution is contained in a glass or carbon or zinc cup as shown, and this acts as the cathode in the battery circuit. This detector possesses the function of acting as its own battery when a carbon or zinc cup is used, as this forms a miniature cell–carbon (or zinc) acid, platinum. This inherent battery action was intensified considerably by using a special amalgam in the acid solution in a detector of this class developed by H. Gernsback several years ago. The self-excited electrolytic detector has never been found (Pierce) to be as satisfactory as the externally excited one, for feeble oscillations.
Another form of electrolytic detector which will stand considerable rough usage is that known as theSealed-Point Electrolytic Detector。The commercial form of this instrument, as here illustrated, is known as theRadioson, Fig. 7. The operation is the same as in the bare-point electrolytic type of detector and a battery of two dry cells is used with it, together with a pair of high resistance telephone receivers and having the battery potential preferably regulated by means of a high resistance potentiometer. The advantage of this type of electrolytic detector is that the acid is sealed in, consequently does not spill or evaporate.
A detector of novel design and termed by Professor Fessenden, its inventor, a哈雷特, is shown at Fig. 8. This works on the heat or thermal principle. An extremely fine platinum wire, about .003 inch in diameter, was first embedded in the middle of a silver wire having a diameter of about one-tenth inch. This compound wire was then drawn until the silver wire had a diameter of about .002 inch; as the platinum wire within it was reduced in the same ratio, it would be drawn down to a final diameter of .00006 inch. As shown in the illustration (Fig. 8), a short piece of this extremely fine platinum wire is supported on two heavier silver wires, and the leads are taken out thru the outer glass bulb for the purpose of connection in the radio receiving circuit. The tip of the fine platinum wire loop had previously to be immersed in acid to dissolve away the silver before the whole device was finally sealed up and the air exhausted from the containing bulb.
当振荡电流通过极细的铂线圈流动时，它变得加热并迅速增加其电阻。其中一些哈雷特swere usually arranged in parallel and shunted by a telephone receiver joined in series with a source of current, such as a single dry cell. Hence, any variation of resistance of the barretter loops due to the heat produced by the Hertzian wave currents, would be manifested in the telephone receivers owing to the change in the amount of battery current past thru the circuit.
TheCarborundum Detector, discovered by General H. H. C. Dunwoody, U.S.A., (Fig. 9) involves a marvelous characteristic possessed by a number of minerals, viz., that of rectifying an oscillating (alternating) current of practically any frequency. The carborundum detector in its usual form comprises two rather stiff springs, adjustable as to pressure, between which the carborundum (carbide of silicon) crystal (preferably an extremely jagged, greenish specimen) is placed. A pair of high resistance telephones are shunted across the detector and the incoming Hertzian wave oscillations, representing the dots and dashes of the telegraphic code, are manifested as short and long signals in the phones owing to the fact that the carborundum crystal will pass currentsseveral hundred times在一个方向上比在反向方向上更好。通过将晶体安装在大截面的杯子或夹具中来提高该动作，使得非常小的接触面积的第二电极。用钢针有效地使用，因为小电极，并且在一个商业仪器中，较小的电极由几个与木炭接触的钢针制成。
Thus, the high frequency oscillations, or, rather,groupsof oscillations, are rectified and the summation of each train of waves reacts on the ‘phones. Battery current usually intensifies the action of the carborundum detector but its polarity must be watched, as also the potential applied. A potentiometer is best employed to regulate the current applied to the detector.
一个最着名的无线电探测器之一，而且现在正在广泛使用的之一是硅探测器。This is illustrated at Fig. 10 and employs a piece of the mineral Silicon embedded firmly in a brass cap. A solder or low heat alloy such as, Hugonium metal is best used in mounting such minerals, so as not to injure their radio detecting properties or sensitivity.
The Silicon detector is generally used without any battery and acts as a rectifier, similarly to the carborundum detector. A pair of 2,000 ohm ‘phones or higher resistance ones, are shunted across the detector usually and owing to the rectifying action already described, the incoming Hertzian wave currents are manifested as short and long sounds in the ‘phones.
At Fig. 11 we have thePerikon Detectordeveloped by G. W. Pickard. This detector consists of two crystals–copper pyrites (Cu Fe S2) and zincite (zinc oxide ZnO), held in firm contact against each other in the manner shown. The copper pyrite crystal is mounted in a cup mounted on a spring-actuated rod provided with a suitable knob, by which it can be swung in any direction. Zincite crystals are mounted in a large cup containing several pockets, the mounting of both of the minerals being effected with a low fusing solder, Wood’s metal or Hugonium alloy. The action of the Perikon detector is supposed to be based on the rectifying principle previously described; that is, it will pass current in one direction but not in the other, and thus the incoming radio frequency oscillating (alternating) currents in the aerial are rectified and caused to give a sound in the high resistance ‘phones connected to the detector. This detector is invariably used with a battery of about two cells and the potential applied regulated by a potentiometer. When using a battery the polarity of the current must be such that the positive wire is connected to the copper pyrite crystal.
最敏感的探测器之一，而且由于其极端简单，最受广播业余流行之一，是Galena Detector, Fig. 12. In this instrument a piece of Galena (lead sulfide) is mounted in a brass cup by means of solder or other low fusing alloy and a light phosphor bronze wire called acatwhisker在矿物表面上轻轻地休息。有时难以找到伽利纳的敏感标本，但是这是一个记录问题和经过验证的事实，当获得真正的一流标本时，它几乎没有其他探测器，甚至没有审计。通过Galena探测器和简单的设备接收消息，包括调谐线圈，锡箔和纸张冷凝器和单个高电阻电话接收器，在距离仅为5 K.W的情况下，在距离的距离为2,500英里。Galena探测器实际上从未与电池一起使用，并通过已经讨论的矿物质的矫正原理作用。
TheCrystaloi Detector(Fig. 13) is a very novel instrument and comparatively young as detectors go. The detector does not require a battery and has a sensitivity on par with the average run of mineral detectors. It comprises a hollow drum, or rather disk, as shown in the illustration. This is supported between two vertical spring clips so that the drum may be rotated on its axis until the maximum sensitivity is attained. Practically all mineral detectors and also the Crystaloi are adjusted to maximum sensitivity by a “buzzer test.” An ordinary buzzer and battery, together with a key or push button, completes this important piece of apparatus, and a single wire from the contact screw in front of the buzzer armature is connected to the detector circuit or aerial circuit
Crystaloi检测器有两个金属盘或插入硬橡胶旋转滚筒的两侧的金属盘或插头，其中一侧包含一小块敏感矿物质。两个金属盘之间的空间部分地填充有某些轻金属件的特殊混合物。在调整该检测器时，将旋转滚筒一次移动一点，直到金属件占据其适当位置，在一侧的普通金属盘和另一侧的敏感矿物之间接触。通过蜂鸣器测试电流通过电感的电气电感快速将此动作迅速达到最大。应与该探测器一起使用一对高电阻的手机。与其他矿物检测器相反，只使用一个“CATWH蓟”接触线，Crystaloi使用备件的许多接触点。
TheFleming Valve Detector赫兹的振荡(图14)是基于the principle that if we have a hot or incandescent electrode, and also a cold electrode, both mounted within an evacuated glass chamber, a rectifying action will be created, i.e., that negative electrical charges, such as those from a battery of 30 to 40 volts or even less, can pass from the hot filament to the cold electrode but not vice versa. In the Fleming Valve, the cold electrode takes the form of a metal cylinder surrounding the incandescent filament. This arrangement acts as an electrical valve for oscillating or alternating currents of any frequency. The space between the cold cylinder and the hot filament is therefore said to possess unilateral conductivity. The Fleming Valve possesses a fairly high sensitivity; it is used with a pair of high resistance head ‘phones, a suitable battery and auxiliary regulating apparatus. The wireless receiving phenomenon occurring will be evident from the foregoing and is in a sense of a rectifying nature similar to that possessed by the mineral detectors.
TheAudion Detector(Fig. 15) employs three distinct electrodes as shown, viz., a filament–a grid–and a wing or plate. The grid, composed of a wire member as indicated, is p laced between the filament and wing. The oscillations when they pass thru the Audion detector are subjected to a similar action to that occurring in the Fleming Valve; that is, they are rectified, but in so doing they are claimed to also effect a relay action with respect to a high voltage battery of 40 to 50 volts potential, connected to a pair of high resistance telephone receivers in the wing circuit. Thus, with the Audion it is seen that, owing to the suggested relay action inherent in its operation, it is quite possible and practical to have such an action occurring of considerable magnitude; that is, the ratio, between the amount of energy passing in to the Audion from the antenna circuit, and the amount of energy controlled by the relay or trigger action in the high voltage ‘phone circuit may be quite large. Several years ago, when the first radio transmission was being tried out between Honolulu and San Francisco by the Federal Telegraph Company, it was found that due to the extreme sensitivity and amplifying action of the Audion, the signals could be copied several hours longer each morning than with any other detector; the signalsfadingas dawn approached, owing to the supposed ionization of the upper atmospheric strata by the sun’s rays.
There was, for a number of years, a great controversy on between the de Forest and the Marconi experts as to the validity of the Audion patents. This matter was discust in the November 1916, and also in the December 1916, issues of this journal and those interested had best read both of these excellent articles as well as a very exhaustive article explaining the action of the Audion which appeared in the August 1916, issue of THE ELECTRICAL EXPERIMENTER.
从本次审查中省略的一个重要早期探测器是“不完美的接触”，其中一个常见的形式包括一块在金属上轻轻搁置的碳棒。这是提供信号的音频接收的第一技术之一，并且在大约1900到1905中使用，直到由更敏感的电解和晶体检测器供应。
