Depth vs Speed (mph)

[Albertan]

Originally Posted by Waxy

P.S. For those running Lowrance units - your sonar settings will also affect your ability to read bottom at depths greater than about 60-70'. If you're set to "Shallow Water", it will cut out at those depths, you have to switch over to "Fresh Water".

So then what advantage does the shallow water setting offer running in under 60'? For those of us who fish shallow (<40') and deeper (100'+), is there a disadvantage to just setting our MFDs to "Fresh Water"? Thanks Waxy.

[Ozark Bob]

I have had Lowrance and Humminbird. I keep a bottom reading and can see the creek channel and trees in spots at 225' Going 52 mph(my top speed). Transom mount on a Lund 2025. the depth is not the problem. It is the transducer placement. Larger transducers are harder to tune. A separate small 2D ducer is easier, Bob

[Waxy]

Originally Posted by Albertan

So then what advantage does the shallow water setting offer running in under 60'? For those of us who fish shallow (<40') and deeper (100'+), is there a disadvantage to just setting our MFDs to "Fresh Water"? Thanks Waxy.

I think it gives you a little cleaner screen (I'd guess it adds a hint of surface noise rejection) and maybe amplifies the arches a bit, but I don't see a whole lot of difference between the two settings. Others may have more to add if they've experimented with them.

I prefer Shallow, but often run Fresh as my default when I'm bouncing between spots on lakes that are regularly over 60-70' ft deep so I'm not losing bottom and readout.

Waxy

[Waxy]

Originally Posted by Ozark Bob

I have had Lowrance and Humminbird. I keep a bottom reading and can see the creek channel and trees in spots at 225' Going 52 mph(my top speed). Transom mount on a Lund 2025. the depth is not the problem. It is the transducer placement. Larger transducers are harder to tune. A separate small 2D ducer is easier, Bob

Wow. The physics of seeing those objects in 225' of water at 52 mph are challenging.

That transducer must be placed and tuned perfectly.

Waxy

[Ozark Bob]

5 different transducers. Usually only a couple adjustments. Had more trouble with the mega transducer.(about 7 inches long) I did decide to hook up a "Y" cable to that and put on a 2D only and raise the expensive one a couple inches above the bottom of the hull. Smaller is always easier to dial in. Bob

[Ozark Bob]

As far as physics sound travels about 5 times as fast in the water. That's about a mile per second. Most 2D transducers fire 200 khz per second(that is 200,000). You are not going to outrun the returns.

[justaguy2454]

Like previously said that mega transducer is on a step hull so completely wrong placement for a good reading from that transducer. Look for a in hull transducer or put on in.

[Waxy]

Originally Posted by Ozark Bob

As far as physics sound travels about 5 times as fast in the water. That's about a mile per second. Most 2D transducers fire 200 khz per second(that is 200,000). You are not going to outrun the returns.

True, but the speed of sound is only a part of the equation.

You have to factor in signal frequency, signal strength, signal dispersion/loss, water density and clarity, bottom composition, etc... All important factors in being able to generate a meaningful sonar return and translate that to the screen.

There's also the factor of being able to display something you're passing over at 52 mph on a screen that's scrolling at about 0.02 mph. Doesn't leave a lot of room for resolution.

Waxy

[Ozark Bob]

Originally Posted by Waxy

True, but the speed of sound is only a part of the equation.

You have to factor in signal frequency, signal strength, signal dispersion/loss, water density and clarity, bottom composition, etc... All important factors in being able to generate a meaningful sonar return and translate that to the screen.

There's also the factor of being able to display something you're passing over at 52 mph on a screen that's scrolling at about 0.02 mph. Doesn't leave a lot of room for resolution.

Waxy

All factors. I don't see fish at speed(maybe little dots) but that's not what I need. I can see trees drop offs and creek channels. Don't need much of that either but it is there at 52. I think outboard noise at that RPM is the biggest factor. HB has an adjustable filter to get a better view. It also affects what shows up. Too much filter and no details,its a compromise any way you look at it. Another factor is the position of the ducer in reference to hull protrusions (strakes and rivet lines can roil the flow under the ducer) just an inch or 2 to one side or another makes a difference. Bob