Re: Fish Finder Tutorial
Good source 5-cents.
Here is a number of questions I asked a Gregg Walters at Techsonic (Hummingbird) and his reply.
Let me try to answer your questions one by one:
"First, how does the PTP wattage affect the performance of a fish finder and is there really a visible difference between 1,500 and 2,000 watts PTP?" PTP or Peak-to-Peak is one way to measure the amount of power from an AC signal. If you had two sonar units that were otherwise identical, the one with the higher output power rating (PtP) would be able to read to deeper depths. Think of it as someone yelling and someone else yelling even louder. Which would you be able to hear from farther away? If you have need of a deep water sonar unit, buying the one with the more powerful transmitter rating (PtP) could be the best choice. Unfortunately it is not this easy as there are other factors that come into play. The biggest being how sensitive the receiver is and how much power loss there is in the conversion of the electrical AC signal energy into acoustical (sound) energy and back again. These specifications are seldom ever printed, hence, transmitter power rating - whether stated as a Peak-to-Peak wattage or an RMS wattage - is a Marketing tool to sell depth sounders. It does not always make a difference. For instance; we use a 800 watt PtP (100 watts RMS) transmitter in another product to be able to read down to 600 feet. However, sometimes a more powerful transmitter can allow you to detect smaller sonar signals that a less powerful transmitter may not. More transmitted power into the water means that the signals reflected off of a target should also be louder. Objects in the water that are smaller, will generally reflect less acoustical energy back to the sonar units transducer. If the sonar unit's receiver is capable of processing these additional signal levels and if the display is capable of showing them, than a difference could be seen. There is really more to it than this but I did not want to get too deep (excuse the pun) into depth sounder operation. With all that said, I doubt that you would be able to see little if any difference between a 1,500 watt PtP sonar unit and a 2,000 watt PtP sonar unit while in 20 to 100 feet of water.
"What does RMS stand for and how does this affect the performance of the finder?" RMS stands for Root Mean Square and it is another way of measuring the amount of power from an AC signal. Purists will tell you that RMS is the only true way to measure the amount of power from an AC signal. The relationship of RMS to Peak-to-Peak is RMS x 8 = Peak-to-Peak. So when you are selling depth sounders, the Peak-to-Peak rating sounds more impressive. Marketing strikes again!
"What is the advantage of the RTS?" One of my favorite subjects and a vastly underrated feature! RTS stands for Real Time Sonar. It is a display of what is under the transducer at that instant. "That instant" being that it can be updated at 40 times a second (according to the depth). What this shows is much like the old bulb type flashers except that instead of the presentation being in a circular format, it is in a vertical format. RTS has the advantage over older flashers in that it not only updates faster (old style flashers updated at 30 times a second), it can show signal strength that non-color flashers could not and it can also show a history of that information (the normal chart portion of the display). The RTS window can show signal strength in two ways: with differing shades of grayscale (16 at present) or as a horizontal line that is longer for stronger signals and shorter for weaker signals (at present 180 different signal strength levels).
"What is the advantage of having more vertical pixels than horizontal (i.e., why 640x320)." The idea behind having more vertical pixels is so that you have better "displayable resolution". If you had two depth sounders that were showing 40 feet of the water column and one had 480 vertical pixels and one had 640 vertical pixels, each Pixel in the 480 unit would equal 1 inch while each pixel in the 640 unit would equal 0.75 (3/4) inches. The formula to figure this out is: Vertical Water Distance/Vertical Pixel Count (remember to convert feet to inches). This does not mean as much in shallow water as it does in deeper water: 200 feet of the water column - 480 equals 5 inches per pixel, 640 equals 3.75 inches per pixel. If the sonar of a depth sounder can 'see' two targets that are only 4 inches apart, the 480 unit would show them as one target while the 640 unit would show them as two separate targets. Horizontal pixels only show a history of columns of vertical pixels - more horizontal pixels means that a depth sounder will show more history, less vertical pixels means the depth sounder will show less history.
Whether or not you would see a lure or any other target under a transducer is determined more by its reflective shape when viewed from above than by what material it is made from. Lures that are thin when viewed from above will reflect little sonar signal back to the depth sounder's transducer. Normally when our Engineering Department tests this, they use a BB which always has a surface that is perpendicular to the depth sounders transducer due to its curved surface. So if you are using a round-head jig, it will be easier for it to reflect the sonar signal back to the transducer than if you were using a flathead jig.
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The two best times to be fishin is when its raining, and when it ain't - Rancid Crabtree.
I am haunted by waters.
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