Encyclopedia of radio electronics and electrical engineering / radio reception

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"Beacon" is designed to set up a training receiver for sports direction finding (TSSP) "across the field" in the absence of GSS. However, such a device is a useful addition to the IPRT. It is possible to make a "beacon *" on just one field-effect transistor, using a quartz resonator as a frequency-setting element. Placed together with a power source in a metal case, the "beacon" has small dimensions and can serve as a signal source, the strength of which can be changed by bringing the "beacon" closer to the receiver or moving it away, as well as changing the length of the antenna used.When the manipulator and a one-dimensional (or shortened, with an extension coil) antenna are used together, the "beacon" can serve as a "fox" in the near search zone (up to several hundred meters).

The "beacon" frequency (3579 kHz) was chosen close to the middle of the operating range of the TCP. and quartz resonators for this frequency are widely available.

The schematic diagram of the beacon is shown in Fig.1.

In such a scheme, it is possible to quite strongly connect the crystal oscillator circuit to the antenna without the risk of a significant change in the generation frequency. In addition, the circuit is not critical to the power supply voltage: its decrease from 9 to 3 V will only affect the output power of the "beacon", while the frequency will be practically unchanged.

The "beacon" can also serve as a calibrator: for example, in the absence of a GSS, a calibration point with a frequency of 3579 kHz can be plotted on the RTSP scale.

Details of the "beacon" are installed on the printed circuit board (Fig. 2 and 3).

The device uses resistors of the MLT type (or similar), capacitors - KM, K10-7, KSO (or similar). Transistor - any of the KPZOZ or KP307 series. The number of turns L3 depends on the generation frequency (frequency of the quartz resonator ZQ1). frame diameter (winding), winding length (number of layers), winding method (coil to coil, heap, etc.), frame material and ferrite core. Experimentally obtained values ​​for a coil with a 8 mm polystyrene frame from the IF circuits of an old tube TV with a ferrite tuning core: for frequencies of 1 - 1 kHz, the number of turns is 08, the winding length is 3500 mm. winding method - in bulk (turns lie crosswise at an angle to each other), winding in the lower part of the frame, at a distance of 3650 mm from the board, into which the coil frame is inserted with force (or glued) into the hole intended for this. Coil frame length - 42 - 7 mm.

The "beacon" starts working at a supply voltage of about 2.5 to 12 V. At the same time, of course, the radiated power and current consumption change (from 0,25 to 1,2 mA).

For the generation mode, the L1-C2-C3 circuit must be tuned to the frequency of the quartz resonator. Turning on the avometer ("tester") to the most sensitive limit of measuring alternating current, we connect one wire of the tester to the antenna jack (XW1), and the other to the body (common wire) of the "beacon". By applying the beacon supply voltage, rotating the ferrite tuning core of the L1 coil with a dielectric screwdriver, we achieve the maximum deviation of the avometer needle.

IF all the details of the beacon are in good order, the installation and winding of the L1 coil are done correctly, the beacon setting ends here. Otherwise, you should check the serviceability of the parts, the correspondence of the ratings indicated in the diagram, the correct installation, or adjust the number of turns of the L1 coil if all the parts (including the Z01 resonator) are in good order, and there is no generation. The same will have to be done if the maximum output voltage of the generator is obtained in one of the extreme positions of the core of the coil L1. If this situation occurs with the core turned out, then the number of turns of the coil is large, and you need to reduce it by 1-2 turns, and then repeat the setting. With the core completely screwed in, you should do the opposite - wind the coil or rewind it with a new number of turns. The maximum output voltage of the generator should be obtained with the position of the ferrite trimmer core in the coil frame L1, close to the middle.

The "beacon" can also be connected to the antenna with the help of a communication coil, connecting one end of it to the antenna socket, and the other to the common wire of the "beacon". The communication coil is wound over L1 and contains 2-3 turns of mounting or winding wire, the diameter of which is not critical (0.3 - 0.5 mm), capacitors C2 and C3 in this case can be replaced by one, calculating its capacitance from the total capacitance of series-connected capacitors C1 and C2 . For frequencies 3500 - 3650 kHz it will be: 89 (pF).

We choose the nearest value (91 pF) of the standard series.

Author: V.Besedin, UA9LAQ, Tyumen

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