Thread: This Dumb, But?

Yep, thats what I understand too, they run at 100% but we control how sensitive the receives set. By turning up or down the gain we're kind of steering the horse by the tail. Turning the sensitivity down increases how much minimum signal it takes to register on the graph, meaning your seeing down a narrower area.
I suppose its because every thing is digital and nothing is really turned up or down, just at what value the software is suppose to start showing marks. You can see that by playing with the Sonar Viewer. All the data is stored, weakest to strongest, you just change the settings for min/max.

I guess its the ham radio operator in me that wishes I could control the output power too but that ain't going to happen. I forgot to say hi to Team9nine back there too. Hope I got it right, maybe Bruce will jump in later and correct me if I'm wrong.
WarrenMN

Just a few things I would add to this discussion:

First off - John I was trying to keep it simple for you. I should have stuck with the flashlight beam analogy but was afraid it would start off the discussion that followed. Not that it is a bad thing but sonar can be pretty complex to understand and most of us don't need to understand it to that level. My point was that just because the sonar displays a fish at 10 feet deep it may not be and without more directional elements in the transducer you just don’t know where the fish is within the beam - just how far away from the transducer it is.

Humminbird uses the -10db point and not the half power point that some other manufacturers use. We feel like this is more of an accurate depiction of what is actually being shown by the unit most of the time. True, objects that reflect more sonar energy back to the transducer can be well outside the -10db area but we felt like the -3db point was not an accurate point to measure from. You will find that the measurement point used is normally determined by what the sonar will be used for. Since the intention was to display sonar targets (hopefully fish) we decided upon the -10db point.

Increasing/decreasing the sensitivity setting on most modern sonar units acts you are turning on and off a filter. Adjusting the sensitivity says: unless you are at least this loud of a sonar return, I’m not going to display you. You turn it down and only the louder returned sonar signals are displayed, turn it up and more are let through to be displayed. Not actually what happens but it’s easier to understand it when you think about it in this way. With monochrome (black and white) units you are also changing what level of greyscale shading you are assigning to each group of returned sonar signal levels. The same happens with color units but most have combinations of colors and can therefore display more signal strength levels at one time. Turning the sensitivity up tells the processor to display a particular signal strength level with a stronger color (if that is how the unit is set to display the sonar returns) while turning down the sensitivity tells the processor to use a weaker color – possibly the same color as the background which effectively makes it disappear.

Although Warren touched upon it, we really haven’t discussed ‘effective cone angles’, how water quality can affect this, and how some materials and fish can be better reflectors of sonar than others… :rolleyes:

Lowrance does have a very good sonar tutorial. Many years ago one of our Acoustical Engineers wrote one as well but for the life of me I don’t understand why our Sales/Marketing folks have not had it added to the Humminbird web site!

Originally Posted by Humminbird_Greg

Just a few things I would add to this discussion:

First off - John I was trying to keep it simple for you. I should have stuck with the flashlight beam analogy but was afraid it would start off the discussion that followed. Not that it is a bad thing but sonar can be pretty complex to understand and most of us don't need to understand it to that level. My point was that just because the sonar displays a fish at 10 feet deep it may not be and without more directional elements in the transducer you just don’t know where the fish is within the beam - just how far away from the transducer it is.

Humminbird uses the -10db point and not the half power point that some other manufacturers use. We feel like this is more of an accurate depiction of what is actually being shown by the unit most of the time. True, objects that reflect more sonar energy back to the transducer can be well outside the -10db area but we felt like the -3db point was not an accurate point to measure from. You will find that the measurement point used is normally determined by what the sonar will be used for. Since the intention was to display sonar targets (hopefully fish) we decided upon the -10db point.

Increasing/decreasing the sensitivity setting on most modern sonar units acts you are turning on and off a filter. Adjusting the sensitivity says: unless you are at least this loud of a sonar return, I’m not going to display you. You turn it down and only the louder returned sonar signals are displayed, turn it up and more are let through to be displayed. Not actually what happens but it’s easier to understand it when you think about it in this way. With monochrome (black and white) units you are also changing what level of greyscale shading you are assigning to each group of returned sonar signal levels. The same happens with color units but most have combinations of colors and can therefore display more signal strength levels at one time. Turning the sensitivity up tells the processor to display a particular signal strength level with a stronger color (if that is how the unit is set to display the sonar returns) while turning down the sensitivity tells the processor to use a weaker color – possibly the same color as the background which effectively makes it disappear.

Although Warren touched upon it, we really haven’t discussed ‘effective cone angles’, how water quality can affect this, and how some materials and fish can be better reflectors of sonar than others… :rolleyes:

Lowrance does have a very good sonar tutorial. Many years ago one of our Acoustical Engineers wrote one as well but for the life of me I don’t understand why our Sales/Marketing folks have not had it added to the Humminbird web site!

Greg,

Thanks for the explanations. They are well written and at a level of technical detail appropriate for our discussion.

Thanks for all the info.

I just purchased the 777c and really like it thus far but a long way from understanding it.

When the users guide says " fish id will show a fish image when a certain criteria is met" or words to that effect, what is the criteria??

can you tell any size of a fish??

Johns

I cannot tell you what the criteria is that the unit looks for to consider a sonar return a fish or not. This is not just that I don't want to get fired but because I don't know. I do know that they do not automatically assume that every sonar target that is not connected to the bottom is a fish. There is something more that they look for but I don't know what that something is.

In short: No.
The sonar return from a fish is influenced by many factors with size and species being just a few of them. The location of the fish within the transducer's sonar beam will also help determine how much sonar signal gets reflected back. So, although we may have set the Fish ID Symbols to display a small sized Fish ID Symbol for a 1 pound Largemouth Bass, a medium sized Fish ID Symbol for a 3 pound Largemouth Bass and a large sized Fish ID Symbol for a 5 pound (or above) Largemouth Bass; this does not always mean that a specific Fish ID Symbol guarantees a fish will be a specific size.

What you may find though is that viewing the Fish ID Symbols (or the sonar without Fish ID) gives you a good indication that a fish is a certain species and possibly a certain size. This is all due to your fishing experience and not just the electronics you have on your boat.