Depth Finders Peak-to- Peak Difference

[settymn]

What is the difference between 2400 peak-to-peak verse 4000 peak-to-peak. My boat runs along about 45mph, will the 2400 keep up with the depth as well as the 4000?

[Greg Walters]

settymn,

A depth sounder with a transmit power of either 2,400 or 4,000 watts Peak-to-Peak should be more than adequate to get the job done. It isn’t always a matter of power though.

The problem normally associated with being able to get and maintain an accurate depth reading at high speeds is that air passes across the face of the transducer – this is true if the transducer is mounted on the transom of a boat or inside the hull of a boat. What normally determines this is the shape and composition of the boat hull, speed of the boat, and how much (if any) of the boat hull is left in the water when running at these high speeds.

A depth sounder doesn’t know or care if it is travelling at a high rate of speed. All it does is transmit a sound wave and listens for the return echoes of this sound wave. Air reflects this sound wave and so the depth sounder does not ‘hear’ where the bottom is and therefore loses the depth reading.

Now it isn’t always possible to get a depth reading at high speed but this is almost always related back to the boat.


Greg Walters at Humminbird

[GU]

Greg,

Does power affect a finders ability to identify fish on the bottom or is it all processor?

TIA,
GU

[GU]

Greg,

Does power affect a finders ability to identify fish on the bottom or is it all processor?

TIA,
GU

[Dodge1]

IMHO, a high vertical pixel count and proper use of the zoom are the most important features for marking fish on the bottom.

[Dodge1]

IMHO, a high vertical pixel count and proper use of the zoom are the most important features for marking fish on the bottom.

[Greg Walters]

GU,

Excuse the lateness of this reply but I’ve been busy with my ‘normal’ job.

No, a depth sounder with a higher power output will not allow it to identify fish near the bottom better than another depth sounder that has a lower power output. This is one of the many depth sounder myths and has been used as a marketing tool for many years now. What a higher power output does is allow the same sonar signal to travel a greater distance (i.e. work to deeper depths) – sort of like the old saying: it isn’t the voltage that kills you, it’s the current”.

There are many things that can affect a depth sounders ability to show a fish on or near a bottom. One is the transducer beam width (a wider transducer beam will have a larger “dead zone”), transmit pulse width, sampling rate (ping rate) and frequency. The processor does play a part in this and so does any filtering or software as well.


Greg Walters at Humminbird

[Greg Walters]

GU,

Excuse the lateness of this reply but I’ve been busy with my ‘normal’ job.

No, a depth sounder with a higher power output will not allow it to identify fish near the bottom better than another depth sounder that has a lower power output. This is one of the many depth sounder myths and has been used as a marketing tool for many years now. What a higher power output does is allow the same sonar signal to travel a greater distance (i.e. work to deeper depths) – sort of like the old saying: it isn’t the voltage that kills you, it’s the current”.

There are many things that can affect a depth sounders ability to show a fish on or near a bottom. One is the transducer beam width (a wider transducer beam will have a larger “dead zone”), transmit pulse width, sampling rate (ping rate) and frequency. The processor does play a part in this and so does any filtering or software as well.


Greg Walters at Humminbird

[JimH]

Greg, glad you popped up here on WC. A quick question? I've had a Legend 3000 for about two years now, it was great on my old boat, an older Starcraft deep V. The dealer added it onto my new one, a Lund 1800 Explorer. I've noticed that I'm getting either a lot of clutter at high speeds or it basically reads blank. I'm sure it's with the postion of the transducer. Am I not getting clean water through it, or am I losing the angle on it, because the bow is slightly higher at high speeds. Any thoughts?

[JimH]

Greg, glad you popped up here on WC. A quick question? I've had a Legend 3000 for about two years now, it was great on my old boat, an older Starcraft deep V. The dealer added it onto my new one, a Lund 1800 Explorer. I've noticed that I'm getting either a lot of clutter at high speeds or it basically reads blank. I'm sure it's with the postion of the transducer. Am I not getting clean water through it, or am I losing the angle on it, because the bow is slightly higher at high speeds. Any thoughts?

[Greg Walters]

Jim H,

Since the unit has been moved to another boat, let’s first make sure that you are not getting interference from something else while you are running:

Start by turning everything else that is electric off. If the problem goes away, turn each piece of equipment back on until the problem shows again. Depending on what is causing it will depend on what you do to eliminate it.

If that does not fix the problem, check to see if it is your main motor that is interfering by revving it while out of gear (don’t get carried away here). If you get interference on the screen of the Legend 3000, try the suggestions in our troubleshooting guide on our web site (http://www.humminbird.com/generic2.asp?ID=434 ).

If none of this points to something else causing an interference problem, than you are most likely getting air under the transducer. You’ve got two adjustments available to you: height and trim angle adjustment. I would start by slightly angling the back end of the transducer downwards. If that does not help (or help enough), try lowering the transducer so that it will run deeper. Other than these adjustments, you would have to experiment with new transducer positions on the transom.


Greg Walters at Humminbird

[JimH]

Thanks Greg, will try your suggestions this weekend.

[GU]

Greg,

Thank you. Very helpful.

GU