SU42160A1 - Superheterodyne Radio - Google Patents

Description

In modern direct gain radio receivers, several tuning loops have to be applied to obtain sufficient selectivity. To simplify the setup, the capacitors of the individual circuits are paired, making it expensive and difficult to construct.

In superheterodyne, they tried to eliminate this drawback by using a very high intermediate frequency and eliminating the contours of preselection. However, at the same time, there was the disadvantage that the high intermediate frequency greatly complicated and degraded the quality of the intermediate frequency amplifier. Therefore, the distribution of such radios have not yet received.

The proposed superheterodyne radio receiver with one tuning loop does not have these disadvantages. The receiver has only one tuning loop, therefore there is no need for complex and expensive paired capacitors and for costly preparation and alignment of the circuits In view of the use of relatively low intermediate frequency, the receiver quality is not reduced. In addition, the setting of the proposed receiver pro (388)

worn out with one handle, since the entire broadcasting range (200-2000 meters) overlaps without a band switch.

On the proposed drawing shows a diagram of a radio receiver according to the invention.

In front of the lamp of the first detector, two filters are turned on, of which one consists of mutual induction coils. 1 and the capacitor 2, the second one from self-induction coils 5, capacitors 3 and 4, and resistances 6 and 7. This filter is equipped with a switch, the slider 9 of which is connected mechanically to the tuning element of the heterodyne variable capacitor 10 to obtain automatic action (as it is shown in the diagram).

The mutual induction coils 1 are turned on and calculated so that the voltage received on the secondary coil, for a frequency equal to the intermediate one, is equal and opposite in phase to the voltage on the capacitor 2. This filter eliminates interference directly at the intermediate frequency.

The intermediate frequency is chosen in the range from 450 kc to 500 kc (average 475 kc) and therefore at these frequencies the receiver has a dip, which, however, is not particularly important. When using the above intermediate frequency, the overlapping of the entire broadcasting range (wave from 200 to 2000 meters) is performed without switching in the heterodyne circuit, even if the capacitor 10 has a maximum capacity of not more than 500 cm.

A filter consisting of self-induction coils 5, capacitors 3, 4, and resistances 6, 7 is designed so that interference at the frequencies of the second interference channel (i.e., superheterodyne settings due to the double-digit setting) is not delayed by the first detector grid got into.

The use of a filter switch consisting of a slider 9 and contacts 8 allows the above conditions to be implemented over the entire broadcasting range. The operation of the receiver when this happens as follows. When receiving stations with frequencies below 900 kc (all figures are given approximately), contacts 8 are closed by slider 9 to the ground and capacitors 4 are driven parallel to capacitors 3, and resistance 6 is parallel to resistance 7. In this case, the filter delays frequencies more than 1000 u. the interference of the frequencies “of the second channel is impossible, since even the lowest frequency of the second channel is (in the case of the intermediate frequency 475 kts) 1504-2 - 475 1100 l: g, lies outside the filter passband.

When receiving stations with frequencies from 900 to 1500 / M, the slider 9, mechanically and electrically connected to the rotor of the capacitor 10, opens contacts 8 (all at once), and the filter in view of the capacitance decrease (capacitors 4 are disconnected) and the resistance increases (resistance 6 ) already blocks the path only for frequencies above 1500– 1600 k.

In this case, the frequencies of the second channel, as well as in the first, go beyond the limits of the filter pass and create no interference, since in this case the minimum interfering frequency will be 900 + 2 475 1850 kz.

B) Avoiding local station interference and eliminating the cross modulation phenomenon; the first detector should be taken with a linear response.

In conclusion, it should be noted that the intermediate frequency of 476 kz is not too high. Such a frequency is used in many modern superheterodyne (for example, the firms Telefunken, Siemens, and others) and the implementation of both sufficient selectivity and amplification at such a frequency is not a problem.

The subject matter of the invention.

A superheterodyne radio receiver with one tuning loop and a filter, characterized by the use of a switch for switching filter steps, the slide of which is mechanically connected to the setting element of the heterodyne circuit.