Tips for users of portable radio stations. Scheme, description

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Tips for users of portable radio stations. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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In this article, the author gives a number of practical tips for those who use Chinese-made portable single-channel radios.

Low-power single-channel portable radio stations ("WALKIE-TALKIE", model "NS 881" and the like), made in China, have become quite widespread in our country due to their low cost, relative efficiency and ease of operation.

The author of these lines had to repair and tune up such radio stations at the request of friends and acquaintances. As a result, the proposed recommendations were born.

Many instances of stations have a weak, muffled sound, devoid of higher frequencies. This shortcoming, as it turned out, occurs due to the excessively strong pressing of the dynamic head, which simultaneously serves as a microphone, to the front panel of the case. Often these parts are fixed skewed, so the head must be reinstalled, making sure that the front diffuser is not pressed close to the decorative grille of the case, and the head itself is placed symmetrically and is not pressed against the body too much. To do this, any suitable gaskets can be placed between the head and the body. As a rule, after such refinement, the sound quality becomes quite decent.

If there are glue or varnish residues on the diffuser, then the head should simply be replaced with a suitable size.

With intensive use of the radio station, the fastening of the lower knee of the telescopic antenna is loosened, which causes a short circuit between the antenna and the printed circuit board. The manufacturer limited himself to carelessly gluing an insulating strip in this place on the lower knee of the antenna, but such a primitive insulation soon ceases to fulfill its functions. This insulating strip must be replaced with a piece of PVC tube, and the lower elbow of the antenna should be glued to the wall of the station housing with "superglue" (cyanoacrylate) or epoxy glue so that the antenna does not rotate.

In addition, sometimes the hole for the antenna in the upper part of the radio station case becomes loose. In this case, the use of a piece of a mechanically strong tube made of a solid insulating material (for example, polyvinyl chloride) of a suitable diameter and thickness will also help.

The radios in question use simple, high-bandwidth, super-regenerative receivers. Even a significant deviation in the frequencies of reception and transmission of devices from the same set does not make it possible to identify this drawback when checking in a store, when test communication is carried out at a distance of 3 ... 5 m. In some instances, the departure of the operating frequency from the nominal value (27,125 MHz) was up to 1,5 MHz (!). It was only possible to find out with the help of a measuring device. Fortunately, these products have only one frequency tuning element - the contour coil trimmer. Therefore, with a frequency meter or a well-calibrated receiver (for example, with a digital scale) and, of course, with the necessary skills, tuning can be done without much difficulty.

At the end of the tuning, the trimmer must be fixed in the coil with cerisin, wax, paraffin, stearin, or even just plasticine to ensure acceptable stability of the operating frequency.

In the instructions attached to such radios, unfortunately, there is no clear indication of the need to extend the telescopic antenna to its full length during operation. And this is very important, because it is an integral part of the only oscillatory circuit in the apparatus, and its dimensions significantly affect the accuracy of tuning the station to the operating frequency, which affects the communication range.

Author: Pavel Mikhailov (RV3ACC)

See other articles Section Civil radio communications.

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