Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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When conducting communications using a portable radio station in stationary conditions, it is advisable to power it from a network power supply and use an external stationary antenna. But at the same time, certain inconveniences arise due to the fact that power cables and antennas will interfere. These inconveniences can be eliminated by using an external microphone PTT or headset. In this case, you can install the radio station in a place convenient for you and control the RX / TX mode remotely. Most modern portable radios allow this mode to be implemented. The proposed schemes can help you assemble remote headsets or a PTT for radio stations with a two-pin switching circuit.

The diagram of the microphone tangent is shown in fig. 1, and for its manufacture you will need an electret microphone, a small-sized button (for example, PKN-150 or PKN-159), a plug suitable for the connector on the radio station, and a shielded wire of the required length.

The microphone and button must be placed in a metal or metallized housing, which must be electrically connected to the shielded wire braid. For electrical and acoustic isolation of the microphone, it must be wrapped with a strip of foam rubber and only then fixed in the case. To allow sound waves to pass through, make several small holes in the case. Almost any electret microphone can be used in the design, for example, from a Chinese-made telephone set.

To free your hands while working on the air, it is useful to use a headset that combines a microphone and headphones, as well as an RX / TX switch, which is most conveniently made in the form of a pedal. A possible scheme for connecting such a headset, consisting of a multimedia (computer) micro-headset and a pedal, is shown in fig. 2.

It contains jacks for connecting stereo phones XS1 (Jack 3.5 stereo) and microphone XS2 (Jack 3.5 mono), placed in a separate metal (metallized) housing. The socket XS2 must be electrically isolated from the housing. Connection to the radio station using the XP1 and XP2 plugs, corresponding to the sockets on the radio station case, and the pedal button is made with shielded wires.

Before the final assembly of the devices, you must first assemble the layout and check the performance of the microphone - the volume and quality of the modulation.

Author: I. Nechaev (UA3WIA), Kursk

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