Patent GB-191329946-A (GB)
Title: Improvements in and relating to Transmitting Arrangements for High Frequency Telegraphy and Telephony.
Inventor: ARCO GRAF GEORG VON
IPC: H03B19/03
Filed: 1913-12-30
Granted: 1915-07-15
Abstract: 29,946. Arco, G. von, and Meissner, A. Dec. 30. Frequency, changing; transformers.-Relates to methods of producing electric oscillations by the polarized transformer method in which the frequency of the supply current is doubled or multiplied by static transformers having directcurrent magnetizing-windings which saturate the cores so that the transformer units act as unidirectional alternating-current resistances. Various methods of producing the odd and even harmonics of the supply current are described, and several transformer units, each capable of producing at will either odd or even harmonics, may be associated so that by a suitable adjustment of various switches, a large range of frequency may be obtained in the aerial without varying greatly the speed at which the supply generator is driven. Each unit 10, Fig. 1, consists of a ring-shaped core having primary and secondary windings 14, 15 and a direct-circuit auxiliary winding 18 which saturates the core, so that the transformer acts as a unidirectional alternating-current resistance. The closed iron core is built up of insulated layers of laminations separated by air spaces, the windings being arranged with air spaces between the individual layers and windings. The whole may be immersed in oil which flows between the windings and between the layers of iron. The effective (R.M.S.) ampere turns of the high-frequency windings should be approximately equal to the ampereturns of the direct current. In the system shown in Fig. 1, currents from the generator 1 having a frequency of the order of 10,000 are doubled in frequency by the unit A, and these currents then have their frequency doubled by the unit B, a final doubling of frequency being effected by the unit C, the secondaries of which are connected to the aerial. The transformer units 29, 30, 31, 32, Fig. 5, may be arranged in the four arms of a Wheatstone bridge, one bridge connexion containing the supply generator 1 and the other a transformer 34, which supplies current of doubled frequency to a similar set of units. This bridge arrangement may be modified so that two of the units are replaced by an inductance, in which case the windings 36, 37, Fig. 6, of the two other units may be wound on a single core 38, which also has two directcurrent windings 39, 40. The windings 36, 37 are wound in opposite directions, so that for a half wave one is of high, and the other of low, inductance depending on its direction, with the result that the successive half waves pass through the transformer 34 and give a double frequency wave. If one or more unidirectional alternating-current resistances are arranged with their alternating-current windings in an oscillation circuit, it is found that higher frequencies may be filtered out from this circuit by connecting to it an oscillation circuit tuned to this higher frequency. In the arrangement shown in Fig. 7, the two units 12, 13 are connected with their alternating windings 14, 16 in series in the circuit of the high-frequency machine. The direct-current windings 18, 19 magnetize the cores 12, 13, in opposite directions. By means of the transformer 41, it is possible to obtain all the higher frequencies, particularly the third, fifth and further odd harmonics. If a single unit 10, Fig. 8, is connected in series in the alternating-current circuit, the second and other even harmonics are specially strong. In the modification shown in Fig. 9, the alternating-current windings 14, 16 are arranged in the supply circuit, and the direct-current windings 18, 19 are provided with a " tuned short circuit " 43, which is adjusted to twice the primary frequency. As shown in Fig. 10, a tuned short circuit 44 is connected to additional windings 15, 17 so as to be independent of the direct-current circuit. Each unit may be used several times for increasing the frequency, as shown in Fig. 11, in which the secondary current from the units B is led back to the primary windings of the units A. The circuit 27 is provided with means 22, 23 and 47, 48 for tuning it to the two frequencies which it carries. In another arrangement, the disadvantages arising from the use of sharply tuned circuits are avoided by making the damping of the intermediate circuits high so that they become approximately aperiodic. The methods of obtaining the odd and even harmonics of the fundamental frequency which have been described, may be associated in such a way that a large range of frequency can be obtained with the use of few transformer units. In the arrangement shown in Fig. 12, the units A, B, C, the windings of which are shown without iron cores, can be connected as desired with one another, and with the generator 1 and aerial 2 and other tuned circuits through switches D, D', D<2>, D<3>, E, E<1>, E<2> and F. Thus, if the switches D, F are connected to the contacts a, the aerial receives double the frequency of the generator 1, while if the switches D, D<1> are set to contacts a and the switch F to the proper contacts, the aerial receives the four-fold frequency. Similarly if the switches D, D<1>, D<2> are all set to contacts a and the switch F to contacts c, the eight-fold frequency is obtained. The system shown in Fig. 7 can be obtained for the first unit A by setting the switch D to contacts b and the switch F to contacts d. A threefold frequency is thus obtained, which can be raised to nine-fold by closing the switch E so as to bring in the tuned circuit 42. Similar arrangements for the units B, C can be obtained by moving the switches D<1>, D<2> to contacts band by closing the switches E', E<2>. The system shown in Fig. 10 can be obtained for the unit A by setting the switches D to a, D' to c and F to g. Similar circuits can be made for the units Band C. By setting the switch G, the direct-current source 21 can be connected at will to the units A, A and B, or A, Band C as required. The switch G and its associated keys &c. are used for telegraphy, while the switch H, microphone 76, &c., are used for telephony. In order to facilitate the tuning of the various circuits, adjustable ohmic resistances are preferably provided in the various circuits and in the aerial, which at the beginning of the tuning operation are in series with the circuit and can be gradually cut out as the condition of resonance is obtained. Troubles due to the necessity of sharp tuning may be minimized, as previously described, by increasing the damping of the intermediate circuits so as to make them practically aperiodic.