Comparison Humminbird PiranhaMAX 197c vs Rivotek Fisher 25 Dual

the maximum depth at which the sonar locator (see "Type") is able to operate effectively — in other words, how deep underwater the device is able to "see".

It is worth choosing an echo sounder according to this parameter, taking into account the actual depths at which it is planned to be used. Of course, this does not place a certain margin, but within reasonable limits (15-20%, less). For example, it hardly makes sense to specially take a model with a scanning depth of 200 m for a lake with pits of 30-40 m — such devices are expensive, while there will simply be nowhere to realize their full potential, and a powerful signal can also scare away the fish. But for marine or oceanic applications, a depth of a kilometer or more may be required; the most advanced echo sounders are quite capable of providing it.

The frequency(s) of radiation at which the device with the echo sounder function is capable of operating (see "Type").

The higher the frequency, the better the resolution and noise immunity of the device, the better it is suitable for working at high speeds, but the range and coverage suffer. Low-frequency (up to 200 kHz) sensors, on the contrary, "reach" deep and cover a wide angle, but are sensitive to interference and do not work well with fine terrain details and small objects. Accordingly, the first option is considered optimal for shallow depths and high-precision topographic measurements, while the second option is for deep water bodies, as well as for searching for fish and other tasks that require wide coverage.

Models with several radiation beams (see “Number of radiation beams”) often provide different frequencies for individual beams, which allows you to combine the advantages of different options in one device and compensate for their disadvantages.

The angle covered during operation by the transducer of the echo sounder (or an instrument with such a function, see "Type").

Technically, the wider the angle, the better the echo sounder is suitable for finding fish and other underwater objects, because. a large coverage area reduces the likelihood of missing prey. On the other hand, to accurately determine the depth, the beam must be as narrow as possible. This is due to the fact that the depth is determined by the maximum protruding point that fell under the beam; thus, if the size of the hole at the bottom is smaller than the spot from the beam, the device simply will not notice this hole. The smaller the angle (and, accordingly, the projection of the beam onto the bottom) — the less likely this phenomenon is.

However, it should be taken into account that all of the above is unambiguously true only for single-beam echo sounders (see "Number of radiation beams"). But multibeam models, usually, combine beams of different widths, thus compensating for the shortcomings of narrow and wide angles. In them, the total radiation angle describes only the dimensions of the space covered by the device.

The power output by the fishfinder (or fishfinder-chartplotter, see "Type") when operating.

The more powerful the emitter, the more “long-range” the device turns out, the greater the depth at which it can work normally (see above). However, do not forget that the practical capabilities of an echo sounder depend on a number of other parameters, ranging from operating frequencies and angles (see above) to the quality of the receiver and the features of signal processing algorithms. In addition, different manufacturers may indicate different types of power in the characteristics: in some cases it is peak (maximum power at the time of a single pulse), in others it is RMS (rms power calculated over a certain period of time and obtained below peak). Therefore, we can say that the role of this parameter is usually purely reference, and when choosing, it is worth focus on moments that are closer to practice (for example, the same scanning depth).

— Screen size. Diagonal screen size in inches. The larger the screen, the more information can be displayed on it and the more detailed this information can be. On the other hand, this parameter noticeably affects the dimensions of the device, and large screens are expensive, especially since you need the appropriate resolution for normal image quality (see below).

— Touch. The presence of a sensor in the design of the display. This feature allows you to control the device by touching the icons on the screen — similar to how it is done in smartphones and tablets. Touch control provides more options than the classic one, using buttons and switches, besides it is more visual — however, such devices are more expensive.

— Display resolution. Display size in dots (pixels) horizontally and vertically. The higher the resolution, the more detailed image the screen is able to produce, the smaller objects can be clearly displayed on it and the more comfortable viewing. At the same time, the specificity of echo sounders is such that too high resolution is not required even for high-end models: for example, modest by the standards of smartphones or tablets 640x480 with a 5" screen are considered quite sufficient even for an advanced device.

— Colour. The ability of a screen to display colours. In this case, the simplest division is used:

Monochrome.... Displays that display information only in shades of one colour. Theoretically, the main colour can be any, but in this case, the vast majority of monochrome screens are black and white. Their advantages are low cost and energy consumption, as well as good visibility in the sun; at the same time, such an image allows you to work with quite a variety of types of data, which is enough even for very advanced echo sounders (see "Type"). However, this variety is not as wide as for colour displays, as a result, for chartplotters (see ibid.), such an image is not suitable — if it is impossible to display different colours, some of the important information on the maps is lost.

Coloured. Screens capable of working with multiple colours. The variety of colours can be quite small, but the image still turns out to be more informative than black and white: different colours can indicate different depths on the map, water temperature changes, etc. Due to this, this type of display is found in all types of navigation devices (see above). Its main disadvantage can be called a higher cost than that of monochrome screens.

— Backlight. The screen has its own backlight system. This feature makes the display independent of ambient light and allows you to see the information on it even in complete darkness. At the same time, the backlight increases power consumption, which is important during long-term operation from an autonomous source (for example, a boat battery). Therefore, it can be turned off.

— 3D maps. Support for maps rendered using 3D graphics. This provides additional visibility in the work: the relief on the screen can be seen not in the form of conditional lines and colour spots, but in the form of protrusions and depressions, the shape of which most closely matches the real shape of the surface. In this case, the three-dimensional image can be supplemented with colour and/or numerical indication to clarify additional data (for example, specific depth values). This feature is typical for high-end models with the chartplotter function (see "Type").

— Sound alarm. The presence of an audible alarm in the design of the device. The types of alarms and their triggering situations can be different: fish detection, critical depth reduction (see “Shoal/Shoal” below), reaching a checkpoint, man overboard(see below), etc. However, anyway, this type of notification is more reliable than graphic indication on the screen — the user does not have to look at the device to hear the sound. This greatly reduces the risk of missing an important message.

— Determining the distance to the fish. Ability to determine the distance to the fish detected by the echo sounder. Usually, we are talking about the distance in depth, and the indication itself can be carried out in different ways: in some models, fish marks are displaye...d opposite the depth scale, in others, a specific value can be given for each mark separately.

— Indication of symbols in the form of fish. The ability to display on the screen a signal from a fish detected by an echo sounder in the form of, in fact, “fish” icons. This option is better suited for non-professional users than standard icons in the form of arcs of various shapes: working with arcs requires some practical knowledge to distinguish fish from other signal sources, and in the case of “fish”, the device itself solves this task for the user. Of course, no such system is perfect, and therefore false positives are not ruled out; on the other hand, recognition technologies are constantly improving. Many echo sounders with this function even have a gradation according to the size of prey — large, medium, small.

— Indication of fish in real time. In devices with this function, fish signals are displayed on the screen when a fish enters the echo sounder beam — and disappear when it leaves the beam. This allows you to track the movements of potential prey as quickly as possible and evaluate the prospects of a particular location — while models without real-time indication display marks constantly, upon detection of fish, and make it difficult to assess its movements.

— Fast screen refresh. The refresh rate of the echo sounder screen determines how evenly the relief “visible” by the device is drawn on this screen. This parameter is important when moving at high speed: if the screen is updated slowly, there is a high probability of the appearance of "steps" with sharp drops — due to the fact that the device did not have time to process and display data on the bottom section passed. By “fast” update is meant a mode that allows you to comfortably use the echo sounder at high speed; for different manufacturers, the specific values \u200b\u200bof this speed may vary, however, usually, we are talking about at least 30 – 40 km/h, developed by powerful motor boats.

— Shallow water/shallow. This function provides an indication of a critical decrease in depth, fraught with grounding with all the associated unpleasant consequences. The depth at which the alarm is triggered can most often be set at the request of the user.

— Automatic change of depth scale. Automatic change of scale of the image on the screen depending on the depth "seen" by the echo sounder. This function adjusts the screen of the device so that the entire scanned volume of water from the surface to the bottom is completely visible on it, and it is not necessary to move the image up and down to assess the situation. For example, at depths of 35-40 m, a model with auto-zoom can use a 50-metre scale, and when reaching greater depths, switch to 80- or 100-metre, at smaller depths, to 20-metre, etc. At the same time, automatic adjustment "makes life easier" for the user, eliminating the need to adjust the scale manually.

— Displayed depth range. The ability to manually set the device to a specific depth range shown on the display — so that the space above and below this range will be outside the screen. This function can be useful, for example, to search for fish walking in a certain depth range; while limiting the range allows you to get an image on a larger scale than when viewing the entire space from the surface to the bottom.

— Determination of bottom density. The ability to use an echo sounder to determine the density of the bottom surface. A device with this function allows you to determine what is under the vessel — stone, sand or soft silt; this information may be useful when catching some types of fish. In addition, bottom density data is useful when searching for underwater objects — for example, sunken ships are often distinguished by "hard" spots on a soft surface.

— Indication of water temperature. Possibility to display the water temperature on the device screen. The specific features of such an indication can be different: some models show only data on the water in direct contact with the sensor (that is, in fact, the temperature on the surface), others are also able to display data on the thermocline (temperature jump layer).

— Indication of speed. The ability to display the speed of movement on the screen of the device. This feature provides additional information and can be useful even on boats equipped with their own speedometers — getting speed data directly on the sonar / chartplotter screen is often more convenient than being distracted by a separate device. This data can come from different sources — for example, from a GPS module or from a specialized sensor (log).

— Display of the distance traveled. The ability to display the distance traveled on the screen of the device. Features of this function may vary depending on the model: in the simplest devices only the total distance traveled is shown, more advanced ones (usually with a chartplotter function, see "Type") can also draw the route on the map.

— Function "man overboard". As the name suggests, this feature facilitates rescue operations in the event of a person falling overboard. The specific functionality associated with this may vary in different models, but usually there is at least the ability to quickly fix the scene in the device and switch it to the navigation mode to this point. And in more advanced models, DSC maritime radio communications may also be provided, as well as the reception and processing of similar signals from other ships.

The presence of a key illumination system in the design of the device.

The role of this function is similar to the backlight of the display (see "Display"): it makes the keys visible even in complete darkness, allowing you to accurately control the device's functions. Yes, even in twilight conditions, the backlight can come in handy — not all buttons have markings that are clearly visible in low light.

The presence in the design of the device protection against dust and moisture.

This function is realized due to the body of the appropriate design, which prevents the ingress of moisture and dirt on the sensitive elements of the device. It is practically mandatory for modern fish finders and chartplotters (see "Type"), as such devices are originally designed to work near water, where the likelihood of splashing is very high. At the same time, note that the specific degree of dust and water protection may be different.

The IP standard is often used to describe it. The classic designation according to this standard includes two digits, one of which corresponds to the degree of protection against dust and foreign objects, the other against moisture (IP54). Here are the most common options for the first digit in modern devices:

• 4 — protection against objects more than 1 mm (most wires, tools, bolts and nails, etc.)
• 5 — full protection against solid objects, dust resistance (some dust may get inside, but it does not interfere with the satisfactory operation of the device).
• 6 — full protection against dust ingress into the case.

For the second digit, the options are:

• 4 — resistance to water splashes from any direction;
• 5 — resistance to water jets of medium power from any direction (protection against powerful splashes during storms);
• 6 — resistance to powerful water jets from any direction (protection agains...t sea waves)
• 7 — resistance to complete immersion in water to a shallow depth and for a relatively short time — but not less than half an hour to a depth of 1 m.
• 8 — resistance to prolonged immersion in water to a depth of more than 1 m. Possibility of submerged operation.

A specific option is a marking with one number and the letter "X" in place of the second — this means that certification has not been carried out for this parameter. In the case of fish finders and chartplotters, "X" is usually put first — for example, IPX4. This is due to the fact that dust resistance for this class of devices plays a secondary role, and many manufacturers prefer not to spend money on certification of this parameter.

It should also be said that dust and moisture resistance is indicated for the main unit of the device placed on board; external sensors that are lowered into the water during operation must, by definition, be waterproof, so they are not discussed in this case.

The supply voltage required for the normal operation of the device. This parameter allows you to determine compatibility with the intended power supply.

Note that usually a certain voltage range is indicated in this paragraph, which ensures versatility. Of course, it is impossible to go beyond this range: too low a voltage can simply “not start” the device, and too high a voltage can damage the electronics. And even seemingly normal operation with a “non-native” voltage (for example, when an unsuitable power source is accidentally connected) is not an indicator in this case: an abnormal mode anyway will accelerate the failure of the device, and besides, it can lead to displaying incorrect readings .