DE1103992B - Transmitter for delivering low or intermediate frequency signals in an inductive loop - Google Patents

Description

The invention is concerned with transmitters for such signal systems which are driven by the audio frequency (i.e. Low frequency induction are operated and a) an audio frequency transmitter with a transmitter loop, z. B. one arranged around a building and on a number of selected channel frequencies in the audible Area working cable, and b) contains a number of receivers operating on different frequency bands work and close to the transmission loop, e.g. B. inside a building or directly outside of the same, are arranged, and relates in particular to a transmitter for delivering Niederoder Intermediate frequency signals in an inductive loop using an oscillator whose Frequency changed with simultaneous antenna tuning by pressing one or more switches chosen from a group of switches.

In a system of the type specified above, it is possible to make a transmitter usable in which the transmission loop directly from a conventional audio frequency amplifier following an oscillator is fed. However, this method is ineffective if the loop is highly inductive and if the output transformer matched the loop at the lower frequencies used Amplifier produces a smaller current in the loop at the higher frequencies. If the The loop output is adjusted for higher frequencies, the current is adjusted at lower frequencies to be taller. Thus, the efficiency will also be low; with many amplifiers, the amplifier will overdriven if their amplitude is greater than required for the higher frequencies.

A well-known transmitter in which the oscillator circuit and the antenna circuit can be tuned at the same time and in which the antenna is adjusted at the same time, is intended for aircraft or ships and provided with a towing antenna. This arrangement is limited to a few frequencies, and the Loop is neither compulsory nor adjustable over a wide range.

These drawbacks have even more of another known arrangement, according to which also four antennas designed for different wavelengths with tubes connected in push-pull Use of a variable tuning capacitor are provided.

In a further known transmitter arrangement, a coarse tuning of the frequency can be carried out by means of a number of correspondingly coupled operating elements and thus the antenna can also be switched over at the same time and fine tuning can be effected by means of a number of other elements. Je transmitter for delivering low or intermediate frequency signals
into an inductive loop

Applicant:

Multitone Electric Company Limited,
London

Representative: Dr.-Ing. RK Löbbecke, patent attorney,
Berlin-Zehlendorf, Neue Str. 6

Claimed priority:
Great Britain June 26, 1956

Oswald Barber Sneath, London,
has been named as the inventor

however, a separate antenna is required for each frequency and can be used at a reasonable cost Control elements only have a very limited number of frequencies available.

The invention aims to provide a simple device for both the tuning of the loop and for the adjustment of the impedance to create an approximate match for the different frequencies to reach. In addition, the invention is directed to means that allow the transmitter to be preset, to adapt any transmission loop within a wide range.

This is achieved according to the invention in that two groups of buttons and an antenna in the form of a inductive loop are provided, which by actuating one of the first group selected Key is tuned by actuating a corresponding key contact, whereby depending on the actuated Button one or two assigned relays are energized, which respectively correspond to contacts Press to select the loop tuning capacitors and the respective matching taps on a main loop tuning inductor to turn on, furthermore with the pressed key of the first group also the oscillator matched to the same frequency range by actuating a corresponding switch contact is, whereby a corresponding capacitor in the circuit with the inductances of the oscilloscope

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lators is switched, and that the switch of the two-high current loop and therefore avoids problems shielded group independently and optionally operable. If the transmission loops are different, so that by pressing a button the two taps on the transformer are switched in order to tune the group to a certain intermediate oscillator in this way, the counter frequency is between each of those indicated by the first 5, which it is adapted to be proportional to the key row of certain frequency ranges due to impedance. This is usually enough to select a tap on the oscillator inductance if there is not a large change in it obtained as a result of actuation of contacts. Value of the capacitor used for the loop By pressing the second group of buttons there is a given, provided that both the impedance and the corresponding setting of the coordination of the io ohmic resistance are approximately proportional to the loop with the interposition of a button loop length for the extensive contacts under consideration Relay achievable by actuating a switch coming type of loops (or antennas) in order to select a tap on an auxiliary loop tuning inductance for an aluminum wire with a diameter. The device is 3.175 mm, the resistance is more than lines for tuning the loop can through 15 3 ohms and the inductance over 1 millihenry / actuation of a switch for the purpose of transmission of 1000 yards (= 914 m).
Language can be made ineffective. As a transformer, such a normal one can be used

In general, the figure of merit "Q" of a laminated low frequency type will be used in Send loop of the kind under discussion in which case it has such an impedance limited by two main factors: first, 20 would have its impedance when thru the loop resistance, which in fact in the correct system is a multiple of the transformed one The series with the inductance is and the quality »Q« of the (or reflected) impedance of the loop cause it to increase with the frequency and, secondly, to increase it, so that the effect of the iron losses by losses as a result of going through the loop in which practically does not matter. Optionally, such Earth or in the steel structure of a building 25 losses due to the use of magnetic oxide-induced Currents, whereby the loop resistance kernels are avoided.

in fact a shunt resistance to the part A fine adjustment to the preset other loop is and the magnitude of this match loop can be viewed as a first approximation as frequency _{independent oc} j _e r of an invariable impedance at by adding a variable stand. 30 the entire transformer or part of it

From what has been said above, it can be seen that with the same, the number of transformer windings can be switched in parallel to a loop tuned to the selected series in relation to the amplifier to the loop with the on. One of the advantages of the latter grow the frequency would decrease, although an arrangement is that _e 35 would in the transformer such decrease weaker than linearly with the frequency i _ne done only group of taps for both Anquenz as circuit by considering can be used to the loop as well as to the finestel of a loop made of an aluminum wire with a lungsspule, although the EinDiameter of 3.175 mm is obvious, whose position coil and the loop are of course independent adjustment impedance at 2 kHz a little under connected. The fine adjustment coil has a value that is twice the value of the direct current resistance of the 40 impedance and adapts itself to its functional loop, while at 10 kHz it has an almost effect on the superimposed fine adjustment on the increases linearly with the frequency. Wherever a considerable number of frequencies, e.g. B. fifty to transformer taps reached tuning frequencies between 2 and 15 kHz.

It is not important that the loop be fitted to each 45 In addition, a fine tuning coil for Fre frequency can be adapted; in this case it is off quenzabstimmung parallel to the whole Trans Ranging when the loop are switched thereof an average value for a formator or part thereof, is adapted group of three or four adjacent frequencies _{to e} j _ne fine tuning control only some. 'to effect the selected frequencies.

In one embodiment of the invention there are 50. Both fine tuning coils can fit without iron means be designed to switch on the transmission loop to a cores.

Variable number of turns of a transformer - where relays are used for switching, tor or autotransformer and for switching the _s j _{n (} i to reduce their number of relays with two outputs from the oscillator or, if necessary, from pairs of contacts; here, each amplifier connects through capacitors of different 55 relays either a single tap on the transformer values on different taps of the named mator with two capacitors or different AbTransformators, depending on the operating frequency grfff _e with different capacitors; in each of the transmitter (or transmitter), provided This arrangement is connected to the tuning of the loop output, while the other capacitor is connected at any single frequency through the capacitor 60 _only when an additional Resatorwert and the transformed (or reflected) circuit is closed, which the through the z Extremely inductance at the individual tap to which the said relay connected other capacitor capacitor is connected. causes, moreover, with the exit or instead

The required switching operations can either be connected to the former capacitor. on through special contacts on the switches or 65 in this way, five relays with two contact buttons each can be set up can be used to control the frequency of the control oscillator pairs to alternate eight tors or with the help of relays that result from such tuning states.

Switches or buttons are operated, carried out A further simplification when switching can

will. The latter method has the advantage of enabling the output with the transformer

part of the isolation of the control oscillator from the 70 by connecting some capacitor and the

leave the taps used for a higher frequency, when the contacts connect the capacitors for lower frequencies and the connection for the higher frequency continuously, i.e. under: saving a relay connection, can exist. Γη in this case the matching impedance will be below that for the taps, to which one the connection is established; in addition, the transformer is here both by the parallel and also matched by the series connection of the capacitors, and he has to do this be adequately dimensioned when choosing the values for the individual capacitors. Where it is desired To send both voice and simple frequencies, this can be borrowed with the help of an additional Relay or switch are made to the amplifier output with a suitable tap on Transformer to connect directly (as opposed to through a capacitor), being under one suitable tap is to be understood as the transformed inductive impedance of the Loop at a transmission frequency taking into account a modulated low frequency to the output impedance of the oscillator or amplifier. If the transmit amplifier is different than is operated for speech, it can work in C mode, provided that harmonic components are in the Loop can be greatly reduced as a result of the tuning of the loop. That way you can The output stages of the amplifier can be biased so that they are essentially as long no current flows until the oscillator is turned on or keyed. Assets of the company in class C it is also possible to use an output power several times for operation without speech is greater than for voice operation.

In the illustrated arrangement, an amplifier can have a total power of approximately 1000 watts Induce currents of several amperes in loops several hundred meters in length; the energy in the The loop can be around 500 VA.

It should be noted that the illustrated arrangement does not necessarily accurately loop the loop at each setting rather, it serves more to keep their vote fairly precisely.

The circuit diagrams according to FIGS. 1 and 2 of the drawing show exemplary embodiments of the invention. In Fig. 1, which shows the loop tuning, L ₁ denotes the output transformer of a normal low frequency amplifier; This transformer is connected to the various taps of an autotransformer L ₂ via capacitors C ₁ , C ₂ by the optional activation of contacts X ₁ , Y ₁ , Y ₂ , Z ₁ and Z ₂ in the manner described above through relays X, Y, Z , C ₃ and C ₄ connected. If the contacts F ₁ and F _{2 are} closed and the contact X _{1 is} open, the coupling takes place only via the capacitor C ₁ . If the contact X _{1 is} closed, the coupling also takes place through the capacitor C ₂ . When the contacts Z ₁ and Z _{2 are} closed and the contacts F ₁ and F _{2 are} open, the coupling is only present via the capacitor C ₃ . If the contact Z _{1 is also} closed, the coupling also takes place via the capacitor C ₄ . The circuit values are chosen so that the system, when coupled together by capacitors C ₃ and C ₄ , is tuned to a frequency that is between the tuned frequencies obtained when the coupling is only using capacitor C ₁ or C ₃ is used. The capacitors C ₃ and C ₄ normally have a lower capacitance than the capacitors C ₁ and C ₂ . Other frequencies in between are obtained by means of additional contacts W ₁ and Q ₁ operated by relays W ₁ X in the manner described above , with the aid of which a coil L ₄ can be connected in parallel _{to the transformer L 2 as} a whole or with its parts.

The system according to FIG. 1 can be preset for adaptation to any given loop length (antenna length) by means of a switch S ₁ , via which the transmission _{loop L 5 is} connected and with the aid of which the taps on the transformer L ₂ can be counted. An adjustment is effected by a switch ^ and a shunt coil L ₃ .

The contacts ^ are used for. direct connection of the transformer L ₂ to the amplifier output transformer L ₁ for speech transmission.

2 shows an arrangement of two groups of keys M, N, P, T and H, J, K, F for the selection of twenty different frequencies by actuating either individual contact pairs M ₁ , M.,; N ₁ , N ₂ ; P ₁ , P ₂ and T ₁ , T ₂ own call key M ₁ N, P and T without combining, or one of the further rows of contact pairs H ₁ , H ₂ ; J ₁ , J ₂ ; K ₁ , K ₂ and F ₁ , F ₂ having keys H, J, K or F. The actuation of the keys tunes the oscillator in the manner to be described and energizes two of the relays X, Y, Z, W and Q at the same time for the purpose of coordinating the transmission loop. When one of the first four keys M ₃ N, P and T is pressed, one of the contacts M ₂ , N ₂ , P ₂ or T _{2 is} closed and, in this way, a coil L _{6 is} tuned, which is a part of a control oscillator (not shown) with each a capacitor C ₅ , C ₆ , C ₇ or C ₈ forms. The last-mentioned capacitors are arranged according to decreasing capacitance sizes. By pressing one of the keys H ₃ J, K or F at the same time, one of the contacts Lf ₂ , J ₂ , K ₂ or F _{2 is also} closed and an impedance consisting of part of a coil L _{7 is} connected in parallel with the coil L ₆ to increase the frequency that way. The values are chosen so that the actuation of the key M and each of the keys H ₁ J ₁ K and F results in frequencies between those given by the key M operated alone and the N key operated alone.

The coils of the relays which close the respective contacts X ₁ , Y ₁ , Z _1, W ₁ and Q ₁ in FIG. 1 are denoted by the reference symbols X, Y, Z, W and Q. These relays tune the loop circuit in the following way to adapt to the transmitted audio frequency: When the key M or N is closed, the relay F is energized via the contacts M ₁ or JV ₁ , so that the contacts F ₁ and F ₂ in the arrangement of FIG. 1 close. When the P or T button is pressed, the relay Z is energized via the contacts P ₁ or T ₁ , so that the contacts Z ₁ and Z ₂ move into the closed position. When the M or P button is pressed, the coil of the relay X is also excited via the contacts M ₁ or F _{1 in} order to close the contact X _1. Pressing the button H or / is used by virtue of the contacts H ₁ or J ₁ to energize the relay Q. By pressing the button K or F, the relay W is energized via the contacts K ₁ or F ₁ .

In a system used for about 60 watts according to the specified circuit, the output impedance of the transformer L _{1 is} about 15 ohms; the transformer L ₂ has a core transversely

cut from about 25.4 to 38.1 mm ² and a total of about 300 turns; the coils L ₃ and L ₄ are coreless and each consist of 500 turns; the capacitance values of the capacitors C ₁ to C ₄ are approximately 0.7 to 0.05 μΥ.

The above is applicable to transmitter system for more than twenty different frequencies which are shifted from that described in conjunction with the drawing assembly ^1. So a total of fifty-six frequencies can be obtained with eight buttons instead of the four buttons M ₃ N ₃ P and T ₃ with six buttons instead of the buttons //, /, K and F, with four relays instead of the two relays Y, Z and with one relay corresponding to relay X , which gives eight capacitor settings.

Claims (3)

Patent claims: 1. Transmitter for supplying low or intermediate frequency signals in an inductive loop using an oscillator, the frequency of which is changed with simultaneous antenna tuning by actuating one or more switches selected from a group of switches, characterized in that two groups of buttons ( M, N ₃ P ₃ T and H ₃ J ₃ K ₃ F) and an antenna in the form of an inductive loop are provided, which is tuned by pressing a button selected from the first group (M ₃ N ₃ P ₃ T), by activating a corresponding key contact (M ₁ , N ₁ , P ₁ or T ₁ ) , whereby, depending on the key pressed, one or two assigned relays (X ₃ Y or Z) are energized, which in each case have corresponding contacts (-Y ₁ , Y ₁ , F ₂ , Z ₁ or Z ₂ ) to activate the selected loop tuning capacitors (C ₁ , C ₂ , C ₃ or C ₄ ) and the corresponding taps on a main loop tuning inductance (L ₂ ), and with the pressed button of the first group also the oscillator is tuned to the same frequency range by pressing a corresponding switch contact (M ₂ , N ₂ , P ₂ or T ₂ ) , whereby a corresponding capacitor (C ₅ , C ₆ , C ₇ or C ₈ ) is switched into the circuit with the inductances (L ₆ , L ₇ ) of the oscillator, and that the switches of the second group (H ₃ J ₃ K ₃ F) can be operated independently and selectively, so that By pressing a key of the second group, a certain intermediate oscillator frequency between each of the frequency ranges determined by the first row of keys is obtained by selecting a tap on the oscillator inductance (L ₇ ) as a result of actuation of contacts (Jf ₂ , / ₂ K ₂ , F ₀ ) . 2. Transmitter according to claim 1, characterized in that by pressing the second group of buttons (H, J ₃ K ₃ F) a corresponding setting of the tuning of the loop (L ₅ ) with the interposition of a relay (W or Q), which is controlled by key contacts ( H ₁ , J ₁ or K ₁ , F ₁ ) is excited, can be achieved by actuating a switch (W ₁ or Q ₁ ) to select a tap on an auxiliary loop tuning inductance (L ₄ ). 3. Transmitter according to claim 1, characterized in that the devices for tuning the loop can be made ineffective for the purpose of transmitting speech by actuating a switch (V). Considered publications:
U.S. Patents Nos. 2,063,248, 2,186,068,
438 116. 1 sheet of drawings © 109 539/407 3.