Comparison Motorola DP4400 vs Motorola DP2400

The frequency range over which the walkie-talkie is capable of transmitting. This parameter is usually indicated if it does not completely match any of the standard radio operating ranges (see “Frequency Range”). For example, the transmission range is often specified for VHF and UHF models, as these bands themselves are quite wide, and individual walkie-talkies can only use a subset of these frequencies. The opposite option is also possible - wide-range models, whose specs go beyond the standards.

The frequency range in which the radio can receive transmissions. It is usually indicated if it does not coincide with one of the standard ranges of the radio; see "Transmission frequency range" for details.

The maximum power at which the radio transmitter is capable of operating. This parameter is one of the most important: it determines both the range of the device (see above) and the features of its use and registration (for more details, see "Frequency range"). For most models of the "amateur" (conditionally) class, the power level does not exceed 2.5 watts. More powerful walkie-talkies are, usually, professional models of the VHF and UHF bands (for more details, see "Frequency range").

The number of channels on which the radio can operate. Each channel is essentially a fairly narrow subband within the main operating band (see "Frequency range"). The division into channels allows several groups of users to work simultaneously on the same territory and in the same range so as not to overlap on the air and not interfere with each other. The more channels provided in the design of the walkie-talkie, the more likely it is to find a free channel and the better it is suitable for working in conditions of intense extraneous radio traffic. This is especially important for powerful "long-range" models. At the same time, simultaneous operation of several groups on one channel is also possible thanks to subcodes (see below).

— Headset connection. The ability to connect a headset to the walkie-talkie — an earpiece (or headphones) with a microphone. The main purpose of the headset is to free your hands during a conversation. In addition, in noisy environments, an earpiece is often more convenient than an external speaker.

— Bluetooth. Medium-range wireless technology (10 to 100 m, depending on version) for direct communication between different devices. The main and almost the only way to use this technology in walkie-talkies is to connect wireless headsets that allow you to free your hands when talking. Bluetooth can be provided in both portable and fixed radios.

— Speech masking (scrambler). The presence of a speech masking feature in the radio: the built-in encryption module (scrambler) encodes the sound and broadcasts an encrypted signal, which is decrypted by the similar scrambler at the receiving end. The main purpose of this feature is to protect against unauthorized listening and interception of “sensitive” information: even if an outsider tunes the radio to the appropriate channel (or subchannel, see “Number of subcodes”), he will hear only a set of meaningless noises. For correct operation in this mode, the scrambler modules for all users must be identical. Also note that speech masking walkie-talkies may be subject to licensing in so...me countries.

— Voice activation (VOX). The ability to control the walkie-talkie with the help of voice: during the silence of the user, the device works for reception, and when the microphone captures the voice, it switches to transmission mode. Usually this feature is implemented through a headset (see above), which allows you to completely free your hands and makes the use of the walkie-talkie as convenient as possible: you do not have to press the button every time to switch to transmission mode. And to avoid accidental activation due to extraneous sounds, many models with VOX have a sensitivity control that allows you to set the volume level for triggering the switch.

— Volume control. The ability to adjust the volume of the speaker, which allows you to choose the optimal volume level depending on the environment. This feature is present in most modern walkie-talkies, with the exception of only the most inexpensive models.

— Auto noise reduction. The function of suppressing noise generated on the air by extraneous sources of interference, when the radio is receiving. Such noises create a signature hissing sound in the speakers (the same one that is heard when the radio is not tuned). It's useless "ethereal garbage", because when talking, it reduces the intelligibility of speech, and when silent, it wastes the battery charge to reproduce a meaningless hiss (which is also unpleasant to hear). The noise suppressor blocks these noises, thus increasing speech intelligibility and providing silence between phrases. Usually, walkie-talkies with this feature provide setting the level of noise suppression — for optimal separation of the useful signal and background noise.

— Channel autoscanning. The ability to operate the radio in automatic channel scanning mode (for more details on the latter, see "Number of channels"). In this mode, the walkie-talkie independently tunes in turn to each channel in search of a transmission signal. Channels without transmitters are skipped, and when a signal is detected, scanning is suspended — for a while or until a special user command. Thus, the user can listen to all active channels and select the desired one.

— Channel monitoring. The ability to operate the radio in the channel monitoring mode. In this mode, noise reduction is completely disabled (see above), and the user can listen to the unfiltered signal on each selected channel. This allows you to evaluate both the traffic load of the channel with calls and the overall level of interference, and select the optimal communication settings.

— Roger-Beep signal. The presence of an automatic end-of-transmission signal on the radio, the so-called Roger Beep. Such devices, when switching from transmit mode to receive mode, broadcast a special sound signal (usually in the form of a short squeak, hence the name), indicating the end of the transmission. This eliminates the need for the user to specify the change of modes himself (for example, with the traditional word "over") — his interlocutors will receive a signal about this automatically.

— Power saving mode. The walkie-talkie has a special mode designed to maximize power saving and allow you to extend the work without recharging the battery (or changing batteries). This feature is especially useful if you have to carry the radio with you for a long time, only occasionally getting in touch. Specific features in different models may vary: for example, some walkie-talkies in this mode are almost completely turned off, only periodically “waking up” and scanning the channel for activity; in others, specific power saving features can be selected as desired by the user.

— Vibration. The walkie-talkie has a vibrating call feature similar to that used in mobile phones: when a signal is received on the selected subchannel, the body of the walkie-talkie starts to vibrate. This feature can be useful in noisy environments where it is difficult to hear the sound signal from the speaker — or vice versa, in silence, when any extra noise is undesirable.

— Keypad lock. The ability to block the keys of the radio from accidental pressing. This allows you to carry the device in your pocket or tight case, without fear that due to an accidental movement, the settings will go wrong, the transmission will turn on, etc. The lock itself is usually controlled in a way that excludes as much as possible the possibility of its accidental release — for example, by simultaneously pressing two buttons.

— On/off button sound. The ability to turn on and off the beep that sounds when each button is pressed. An audible signal serves as a convenient confirmation of a full press; on the other hand, it may not be appropriate in some situations.

— GPS module. It implies the presence of a built-in module for receiving GPS data from satellites, which allow you to determine the exact location of the user. The accuracy of work largely depends on the number of satellites that see the receiver at a particular moment, and weather conditions, but, usually, it ranges from one to ten metres. The functions of the portable radio with built-in GPS may vary depending on the specific model. So, the device can simply display the exact position at the moment on the screen (latitude, longitude, altitude), as well as the direction and speed of movement. More advanced models with a large screen can show locations on a map or, for example, transmit the user's coordinates to the dispatcher.

The capacity of the radio battery, in other words, the amount of energy that the battery can store. It is standardly measured in ampere-hours: 1 Ah means that the battery, when fully charged, is capable of delivering a current of 1 A for 1 hour. In portable electronics, measurements are typically made in a thousandth of a milliamp hour (mAh).

In general, the higher the battery capacity, the longer the radio is able to work; however, this is true only under otherwise equal conditions. In fact, due to differences in the specs of individual models (range, transmitter power, etc.), their power consumption can also vary significantly, and even situations when a model with a smaller battery capacity of two walkie-talkies will have greater battery life can happen. This is especially noticeable when comparing compact models of "urban" ranges and powerful "long-range" radios that require a lot of energy. Therefore, for walkie-talkies, the battery capacity itself is rather an auxiliary parameter — the operating time in different modes provided by this battery is of decisive importance (see below).

The walkie-talkie has an indicator showing the battery charge level. Its presence allows you to monitor the state of the battery, so that the charge does not run out at the most inopportune moment, and also, in some cases, control the charging process. In this case, the role of the indicator itself can be played by both a simple LED that changes colour or mode of operation if it is necessary to charge the battery, or a full-fledged info on the display (similar to those used in mobile phones).

Walkie-talkies with this feature have a special protected housing that prevents dust and moisture from getting inside and damaging sensitive electronic components. If you often have to be in adverse conditions, you should pay attention to such walkie-talkies. At the same time, note that the specific degree of protection in different models can vary markedly, and here it is most convenient to evaluate it by IP marking. This marking consists of the letters IP and two numbers; resistance to dust — the first digit, resistance to moisture is described by the second, last digit. You can find the following options for protection against moisture:

— 4. Protection against splashes from any direction. Thus, the walkie-talkie will be fine during rain of medium intensity, regardless of the strength of the wind
— 5. Protection against water jets from any direction. Allows walkie-talkie to endure a combination of strong wind with a downpour.
— 6. Protection against strong water jets and sea waves. It is considered the minimum level of protection that allows use near water.
— 7. The possibility of short-term (less than half an hour) immersion under water to a shallow depth (less than 1 m); continuous operation in immersed mode is not expected.
— 8. The highest level of water protection. Allows long-term (more than 30 minutes) immersion under water to a depth of 1 m or more, and even permanent work in a submerged position. However, note that specific restr...ictions on the use in such walkie-talkies may be different, they must be clarified according to the manuals.

Dust protection values are presented more modestly:
5 — dust resistance without full closure (a certain amount of dust can get inside, but it is small and does not affect the operation of the device)
6 — full protection (dust is not able to penetrate inside the case).

At the same time, there are situations when the manufacturer did not test the device for dust resistance, but limited itself to water protection. In this case, instead of the dust protection number, there is an X, for example IPX7.