Concealed VHF radio stations.

Concealed VHF radio stations..

Ovchinnikov Andrey Mikhailovich

CONCEALED VHF RADIOS

The article provides comparative characteristics of foreign portable VHF radio stations that allow the possibility of their concealed wearing, based on the technical characteristics provided by the suppliers of these radio equipment. Some recommendations are given on the selection of radio stations and their adaptation to the tasks of concealed carrying.

Professional VHF radio communication equipment is widely used in the practice of security and safety services. At the same time, it is often necessary to organize their use unnoticed by others, i.e. to provide visual and acousticradio communication secrecy. Along with the use of special accessories for covert radio communication (miniature remote control panels for radio stations, wireless receiver-phones, small microphones, etc.), the size of the radio stations themselves plays an important role. They should allow the radio station to be placed on the operator's body without being noticed by others. A radio station for covert wearing is placed either on the belt, or in the inside pocket of a coat or jacket, or in a special case (like a belt) under the operator's clothes.

Since the domestic market does not offer radio equipment that is specifically designed for concealed carry, security services have to choose from miniature and subminiature radio stations of foreign manufacture. In the catalogs of various foreign companies engaged in the supply of special technical equipment, standard professional radio stations from manufacturers such as Motorola, Icom, Standard, etc. are presented as means of radio communication for concealed carry.

Naturally, when comparing radio stations only by their overall dimensions, the most miniature products will have an advantage. However, since the comparison should also be made by other technical parameters, as well as by cost, it is advisable to identify the criteria by which a VHF radio station can be classified as a means for concealed carrying. With a sufficient degree of conventionality, a radio station can be considered as satisfying the requirements for concealed carrying if its overall dimensions do not exceed:

• height — 120 mm;
• width — 60 mm;
• thickness — 30 mm,

and the weight is within 350 g. For a clearer classification, we will consider a radio station as allowing for concealed carry if its parameters meet at least three indicators, and the thickness requirement is mandatory, since this parameter is the most critical for this class of radio equipment.

Radio stations that meet these requirements are produced by a number of foreign companies, the leading ones being Motorola, Yaesu, Standard, Icom and Alinco.

One of the leaders in this class of equipment in terms of its operational characteristics is rightly considered to be the radio station model VISAR by Motorola. The operational parameters of this radio station comply with the requirements of the MIL STD 810 standard (US military standard) for vibration and shock resistance, dust protection, high temperature and humidity, and low pressure.

The station can be supplied in a “professional” version: with a minimum of controls and a convenient, durable carbon fiber housing. Depending on the frequency modification, VISAR can operate in the following frequency ranges: 146-174 MHz, 403-470 MHz, 450-520 MHz and even 806-866 MHz. The radio station has 16 memory channels. With a certain type of battery, the transmitter output power reaches 5 W, with a battery that provides minimal dimensions, the transmitter power is 1 W.

Photo 2. Radio station C408 from Standard

The excellent technical and operational characteristics of the station determine its significantly higher cost compared to other radio equipment of this class (about $1000).

A wide range of miniature radio stations, which, however, do not meet the requirements of the military standard, is offered by the company Standard. The most popular models are C108 (144-174 MHz) and C408(420-474 MHz). The stations have various scanning modes, 20 memory channels. The products are powered by two AA batteries. Standard output power is 230 mW. Current consumption in all modes (compared to other radio stations of this class) is small. This allows you to operate the radio station without changing the elements for a fairly long time (for a nickel-cadmium battery type CNB401 with a capacity of 500 mAh with a ratio of the station's operating time in the modes «transmission: reception: standby reception» as 1:1:8, the operating time is within 13 hours). Radio stations have the lowest cost among similar products.

The C156 radio station has greater functionality, but also significantly larger dimensions (the height of the station is 1.5 times higher and the weight is 2 times higher than the C108).operating in the frequency range of 130-174 MHz. 100 memory channels, 3 output power gradations, 3 types and 7 scanning modes, built-in tone call device (DTMF), the ability to receive and transmit short, so-called status messages and other functional capabilities.

With a battery that provides minimum dimensions, the transmitter output power is up to 1.8 W, the maximum power is 5 W. Just like the C108, it has a low cost.

Photo 3. Radio station C508 from Standard

Dimensions similar to the C108, and a unique set of functional capabilities with such dimensions are provided by the radio station C508. It operates on reception and transmission in the ranges of 140-174 and 430-470 MHz, and also has the ability to receive in the ranges of 300 and 800 MHz. The radio station allows the ability to work in 2-range half-duplex, has 60 memory channels, Set-mode for programming 23 settings of built-in functions. C508 has 3 types of scanning of receiving channels with the ability to listen to all 4 ranges with a width of 100 MHz, which practically allows considering the radio station as a scanner. Power is supplied by two AA batteries or by a CNB401 battery, allowing the station to remain operational for 10 hours (with a ratio of the time of reception and transmission modes of 8:1 and an output power of 280 mW). With such characteristics, the cost of the station is not significantly higher than that of the C108.

The radio station C510 has similar characteristics with slightly expanded functionality and slightly larger dimensions.. This is also a dual-band radio station (140-174 and 430-470 MHz) with the ability to scan in the 300 and 800 MHz ranges. The station is equipped with a full keyboard and a built-in DTMF encoder and a selective access device (CTCSS). Maximum output power is 3 W.

Another manufacturer of miniature radio stations — ICOM — also, like Standard, produces stations that can be used as radio equipment for hidden carry, without meeting the requirements of military standards. IC-T22 and IC-T42— single-band radio stations, focused mainly on the amateur radio frequency range: IC-T22 operates on transmission in the range of 144-148 MHz (reception — 136-174 MHz), and IC-T42 — in the range of 430-440 MHz (reception 400-470 MHz). The stations have wide functionality: up to 80 memory channels, reception and transmission of status messages, CTCSS, DTMF, etc. With batteries that provide minimal dimensions, the output power is 2 W, the maximum transmitter power is 5 W.

Kenwood produces radio stations of the TH-22AT and TH-42AT models, which are practically identical in technical characteristics and functional capabilities. These are single-band radio stations, also operating in the amateur frequency range. In addition, Kenwood produces a dual-band radio station TH-79A(D), which has dimensions that are only slightly larger than the single-band stations. According to operational characteristics, these models belong to the class of amateur radio stations.

Yaesu produces a large number of models of miniature radio stations that can be carried covertly. At the same time, it produces both reliable professional radio stations that meet individual requirements of the MIL STD 810 standard, and stations aimed at the amateur level. FT-10R, FT-11R, FT-40R, FT-41R — single-band radio stations that differ in frequency range and compliance with military standards: FT-10R, FT-11R — operate in the range of 144-148 MHz (FT-10R also provides reception in a wider range of 140-174 MHz), FT-10R — meets the requirements of the MIL STD 810 standard, FT-11R — is designed for less severe operating conditions;

FT-40R, FT-41R — are designed to operate in the frequency range of 400 MHz; FT-40R, which meets military standard requirements, receives a signal in the range of 420-470 MHz and transmits — in the range of 430-450 MHz; FT-41R — has a frequency range of — 430-440 MHz.

The radio stations differ slightly in size and weight and have almost identical functionality: various scanning modes, a full keyboard and the ability to transmit tone signals, a CTCSS encoder, up to 100 memory channels, etc. At the same time, the cost of stations that meet the requirements of military standards is slightly higher than the cost of amateur radio stations, although it should be noted that the FT-10R and FT-40R stations only meet the requirements for mechanical impacts and dust and moisture protection (unlike, for example, VISAR, which also meets the requirements for resistance to high temperature and humidity).

FT-50R (MIL STD 810) and FT-51R— dual-band radio stations that provide the ability to operate in both 140 and 400 MHz ranges. Like their single-band counterparts, they support a full range of additional functions, in addition, a special feature of these models is the ability to digitally record audio signals.

Photo 5. DJ-C1 radio station by ALINCO

The smallest dimensions among the known miniature radio stations are the DJ-C1 (reception — 118-174 MHz, transmission — 144-148 MHz) and DJ-C4 models.(reception and transmission — 420-450 MHz) by Alinco. Despite the unique dimensions (94x56x10 mm) and weight (75 g), the stations have 20 memory channels, a CTCSS encoder, the ability to scan and transmit a tone call, and other functional capabilities. Alinco models are not equipped with a built-in speaker (which is not so important for hidden carry radio equipment) and are equipped with a small-sized earphone. DJ-C1/DJ-C4 radio stations have a telescopic antenna, as well as the ability to install a flexible wire antenna. The delivery set includes a lithium-ion battery (500 mAh) and a charger for it. Despite the known shortcomings of lithium-ion technology, according to suppliers, more than 100 charge-discharge cycles of the battery are provided. The output power of the station is 300 mW.

The main drawback of these radio stations is the lack of a State Communications Committee certificate for them at present. However, certification work is underway, and there is hope that the station will be certified in the first half of 1998. Upon receipt of the certificate, Alinco models will undoubtedly take one of the leading positions in the market of miniature VHF radio communication devices.

The characteristics of portable VHF stations manufactured by foreign companies, which can be used as radio equipment for covert wearing, are presented in Table 1.

Table 1.

All radio stations presented in the table have the ability to connect headsets to them, oriented towards hidden placement on the operator's body: for some radio stations, such headsets are produced directly by the manufacturers, for others, headsets produced by other companies can be used.

The range of prices for radio communication equipment presented in the table is explained by the presence of different modifications of products and some variations in the cost of radio stations from different suppliers.

When choosing any radio stations, including those that are intended to be used for concealed carry, it is necessary first of all to take into account the frequency resource available, since any security structure must use radio communications only legally. (When using radio equipment legally, it is necessary to first obtain permission from Gossvyaznadzor to use one or more operating frequencies, and then register each of the acquired radio stations with the regional office of Gossvyaznadzor.) If there is a specific frequency, it is quite possible that the choice will narrow, for example, when receiving a frequency outside the 144-148 MHz or 430-440 MHz bands, it is no longer possible to use radio stations oriented to work in the amateur frequency range.

If it is possible to work in any band or if there is a frequency in the amateur range (all radio stations listed in the table operate in it), the choice of equipment is determined by those factors (technical characteristics, reliability, dimensions, cost, etc.) that are most important to the user.

With high requirements for reliability of radio equipment(especially to mechanical strength), and if the cost factor is not decisive, the best choice would be to use VISAR radio stations from Motorola.

If the determining factor is visual stealth of radio communications, it is best to choose stations with minimal dimensions: either micro-miniature models DJ-C1/C4 from Alinco (if problems with certification of these radio communications are solved), or models C108, C408, C508 from Standard.

If it is possible to work in two frequency ranges (140 and 400 MHz) and in cases where in certain situations it is necessary to ensure secrecy of radio communication channels(i.e. to have the possibility of applying some measures against radio monitoring equipment), it is preferable to use dual-band radio stations such as the C508 and C510 from Standard, the TH-79A(D) from Kenwood, or the FT-50R and FT-51R from Yaesu. These stations also have the greatest capabilities for scanning various frequency ranges.

If the determining factor is cost, then the greatest savings in financial resources can be achieved by purchasing the C108/408, C156 from Standard, the IC-T22 from Icom, or the DJ-C1/C4 from Alinco.

According to their functional capabilities (when working in one frequency range), the best indicators are the models C510 from Standard, IC-T22/T42 from Icom, FT-50R/51R from Yaesu.

At the same time, if it is supposed to use radio stations mainly for covert carrying, some factors do not play a significant role. The issues of adapting radio equipment for the tasks of visually covert communication are of greater importance.

For example, wide functionality of radio stations is practically not required when they are carried covertly. On the contrary, if the station has a keyboard and numerous controls, then this is rather a negative factor, since there is usually some possibility of accidentally reprogramming the station or switching the working channel. From the point of view of ergonomic criteria, for security services (especially when carrying radio communication equipment covertly), it is preferable to use the simplest radio stations without a keyboard, without a display, with a minimum of controls. Volume and noise reduction should be adjusted by turning convenient knobs, and not electronically by pressing any buttons. When carrying radio stations covertly, the quality of their work will largely depend on the technical and operational characteristics of the headsets: microphone sensitivity, nonlinear distortion coefficient of the earphone, strength of wire connections, reliability of contacting devices, etc.

Visual stealth is also largely determined by the type of headset used. To ensure maximum stealth, it is preferable to choose headsets that use small-sized omnidirectional microphones, control panels made in the form of a cylindrical drum-type switch with a silent button and having a flesh-colored color, and wireless miniature inductive receiver-phones.

The overwhelming majority of services have extremely limited frequency resources (one or several frequencies in one range) with a limited territory of its use. In such a situation, the use of dual-range stations becomes absolutely unjustified.

A much more important issue is the design of antennas for small radio stations. Except for the DJ-C1/C4 models from Alinco, none of the presented radio stations have flexible wire antennas as a standard delivery set. The use of standard antenna devices makes it extremely difficult to use the stations as radio equipment for concealed carrying, since the significant linear dimensions of the antennas create great difficulties and inconveniences when the operator moves and changes the position of his body. Perhaps only the C108, C408, C508 models from Standard can be camouflaged under the operator's clothing due to their low height. Nevertheless, even for these miniature radio stations it is advisable to use special flexible wire antennas, which can have various designs.

It should be noted that when carrying radio stations covertly, the communication range will always be shorter than when using radio equipment openly. This is explained by the fact that when carrying radio stations covertly, the height of the station antenna is usually less than when using radio equipment openly, and the propagation of radio waves is significantly affected by the human body (for openly carried radio stations, the shielding effect of the human body is much weaker). For radio stations of covert carry, it is extremely difficult to achieve a circular pattern of the electromagnetic field, which is explained by a significant decrease in the communication range in the direction that is “shielded” by the operator's body. It is not always possible to take the most advantageous position for communication in situations involving the covert use of radio equipment. As studies have shown, on averageThe communication range between covert radio stations using flexible wire antennas is 2-3 times shorter than that of conventional stations (with the same power and sensitivity of radio equipment). The shielding effect of the human body increases with increasing nominal operating frequency.

The communication range can be increased by increasing the power of the radio stations. However, with prolonged use of radio equipment and a relatively high intensity of negotiations, for medical reasons it is advisable to limit the transmitter power to 0.5-0.7 W. Therefore, for covert radio stations, it is advisable to achieve an increase in the communication range not by increasing the output power, but by other means.

In general, as in any issue related to the acquisition of technical equipment, when purchasing radio stations that are supposed to be used as covert communication equipment, it is advisable to approach the problem comprehensively: clearly define your requirements for radio communication equipment, think over the necessary measures to adapt the stations to the tasks of covert carry, assess your financial capabilities, etc. If necessary, please consult with technical specialists.