Sonar Power

[3's]

Just wondering what difference the power makes in shallow water lakes?

For instance, Average lake depth is 8 feet with the deeps at around 35. What are the advantages of 4000 watts over 2000 watts if all other features are the same??

[Team9nine]

Just my opinion, but in a lake that shallow there are no real advantages to having the extra 2000 watts. In some cases the extra power can cause some problems reading in shallower water. I've got two units I'm running now, one at 1500 watts and one at 3000 watts and both do great in the depth range you've stated. I don't think you'd have any problems with the 2000 watt unit for the circumstances you've stated.

-T9

[slabbandit]

Correct me if I am wrong but I think more power translates into better target separation.

[Team9nine]

Correct me if I am wrong but I think more power translates into better target separation.

Transducer frequency and vertical pixel count get you better target separation. Power just gets you those things to greater depths. :D At least that's my understanding. As an example, check out a Hummingbird catalog some time. Their 750 watt unit has the same stated target separation (2.5") as their 2400 watt unit.

-T9

[slabbandit]

I wasn't sure but I believe you are right. Higher pixel counts and zoom features probably help with target separation more than power.

[Humminbird_Greg]

More transmit power allows you to read to deeper water depths but it can also allow you to receive sonar returns that a lower power sonar unit may not. The problem with this is that not many units transmit at their highest power level when in shallow water. Doing so would cause shallow water reading problems.

If two units had the same transmitter power and used a transducer with the same beam width, the one with the lower frequency would read to a deeper depth but at the cost of giving up sonar resolution. The reverse is also true: a unit with a higher frequency would only be able to read to a shallower depth but could do so with better sonar resolution.

There are other factors that can affect sonar resolution as well but many get “sonar resolution” confused with “displayable resolution”. The displayable resolution is the vertical distance of the water column that each vertical pixel represents. For a unit that has 120 vertical pixels; when in 50 feet of water, each pixel equals 5 inches of vertical distance. A unit with 320 vertical pixels in 50 feet of water; each pixel represents 1.88 inches of vertical distance. A unit with 480 vertical pixels in 50 feet of water; each pixel represents 1.25 inches of vertical distance. A unit with 640 vertical pixels in 50 feet of water; each pixel represents 0.94 inches of vertical distance. Now if any of those units had a zoom feature that allowed you to look at any 10-foot section of the water column these numbers change to: 120 pixels = 1 inch, 320 pixels = 0.38, 480 pixels = 0.25, 640 pixels = 0.19 inches. Not so many years ago the displayable resolution was a factor in being able to show the available sonar resolution and many remember this but as we can see, the displayable resolution of most of today’s units is no longer a factor since most have a zoom feature of some type. So the vertical pixel count of a sonar units display does not affect its sonar resolution capabilities but it can affect whether it can show them to the fisherman without having to resort to using a zoom function or not. Of course the higher vertical pixel count units do show a ‘prettier’ smoother appearing display due to their smaller sized pixels!

Sonar frequency and some other unadvertised factors (transmit pulse length, transducer Q, receiver filter Q,…) are what determine sonar resolution of Target Separation.