Side imaging

[Humminbird_Greg]

Pete,

You must have missed my post about the latest software update (3.740) for the 987c Si and other Humminbird units. It’s not listed but the Zoom while in Side Imaging and the Sonar Record features are in there along with the rest of the changes. This is where you would really notice the differences in what the 987 and 997 units can do Si sonar wise.

No directions on how to use the Si Zoom, Sonar Recording and other features on the Humminbird web site and I don’t know if they will have any. You can download the operations manual for the 997 as the directions for these are in there and are the same for the 987.

[ShilohRed]

Pete,

You must have missed my post about the latest software update (3.740) for the 987c Si and other Humminbird units. It’s not listed but the Zoom while in Side Imaging and the Sonar Record features are in there along with the rest of the changes. This is where you would really notice the differences in what the 987 and 997 units can do Si sonar wise.

No directions on how to use the Si Zoom, Sonar Recording and other features on the Humminbird web site and I don’t know if they will have any. You can download the operations manual for the 997 as the directions for these are in there and are the same for the 987.

Thanks Greg. Yes I did miss it.
But have been to the website and looked at the 997 manual and have it worked out. Now to get out on the water and find some more great stuff with it.
Pete

[Cane Pole]

Cane Pole,

I can’t recall my electrical theory right now but I know that there is a relationship of 8 when converting RMS to P-t-P in an AC circuit. If you were to look back in time you would see that we used to only use the RMS measurement – not sure why we never used an average measurement. When our competitors started using p-t-p measurements in their advertising and started brain washing the public into “more power is better” we had to end up following suit.

It would be nice to have an industry standard for the power rating and also for the sonar beam widths – another area where the public has been mislead. As an ex-Quality Tech I can tell you that there are a great number of things in this business that there is no industry standard for and that the customer could profit from if there was.

I am glad you understand where I am coming from on these issues and are honest with your answers.

I get quizzed about power and cone angles often. A lot of folks get confused on the coverage of the view at certain depths. Some go by the 1/3 depth area coverage. This is somewhat true for a 20 degree cone angle, but not so close for larger or smaller cone angles.
It is a trig function. It is hard to explain to folks. I wish there was a chart for cone angles/verse coverage at depths. Do you know of such a chart?

Also, when adjusting the sensitivity of the sonar, are we adjusting the amplifier receive level or the transmit amplitude or both? I can’t seem to find the answer anywhere.

These are questions I am asked quiet often.

Thanks,

Tom

[Humminbird_Greg]

Cane Pole,
1/3 the depth is a good rule of thumb for a 20 degree cone angle transducer and there is a formula for figuring the approximate area of coverage for transducers with different cone angle widths. We used to have some depth multiplier numbers on the Humminbird web site for all of the transducers and beam widths that we made but I could not find it when I looked today. If there were a chart available the problem with it would be that you would have to be aware of at what sound level point (db) that the transducer you are interested in was measured at. Some will tell you that the industry standard for this is at the -3db point or that this is where the US Navy measures transducer beam widths at – this is not true. Sure the Navy measures their transducers at the -3db point, but they also measure them at the -6db and -10db points as well as others. It all depends on what the system is being used for and how sensitive the detection criterion is. We specify our transducer beam widths at the -10db point since this more accurately reflects the what the depth sounder is being used for (to show the bottom, structures and any fish that may be between the surface and bottom). The – (minus) in front of the db numbers means that the sonar signal has degraded to this point with the -3db point being what is called the half power point or where the sound level is only half of what it is when directly under the transducer, and the -10db point being where the sound level is one-tenth of what it is when directly under the transducer. Directly under the transducer would be the loudest or strongest sound level area. So you can see that a transducer that measures 20 degrees at the -3 db point would actually show sonar returns over a wider area than a transducer measures 20 degrees at the -10db point. A transducer that measures 20 degrees at -3db would measure 24 degrees at -10db. A transducer that measures 20 degrees at -10db would measure 16 degrees at -3db. So when you compare one product to another, you would need to be aware of what sound level point (db) the transducer beam width was measured at.

Our (Humminbird) more popular cone angle measurements and the approximate area covered are:
20 degrees (@-10db) = depth X 0.35
60 degrees (@-10db) = depth X 1.00
90 degrees (@-10db) = depth X 2.00

This is all nice, mathematical, cut and dry – but this is not telling the whole story. The problem with transducers is that they do not always focus all of their sonar energy in one nice conical area. Although Engineers try to minimize it, they can produce side lobes of sound energy. If enough energy from these side lobes gets reflected back to the transducer, it effectively increases the cone angle of the transducer. Add to this other factors that may be out of our control that can also bring about a change in the effective sonar beam width (water quality, bottom composition and angle, composition of objects in the water, water depth, angle of the transducer to the bottom, transmit power, receiver sensitivity,…).

When attempting to explain transducer beam widths and coverage (that I may have just managed to mangle and confuse everyone with) I like the analogy of the flashlight:
Turn the flashlight on and the light goes out in a ‘beam’. We don’t see the light beam itself but what gets reflected back to our eyes – much like a transducer. We could measure how wide this beam is and use this measurement to calculate just how large of an area the flashlight beam will be covering at a certain distance – just like sonar. Even with the focusable flashlights, we have all seen how there are objects, while not directly in the main beam of the flashlight, that can be seen off to the sides – all due to those pesky ‘side lobes’ of energy and because these objects reflect enough light for us to see them. Objects that are at a right angle to the flashlight beam tend to reflect more light back to you as do objects that naturally reflect more light – same with sonar and sound. Now that flashlight beam does not go on forever and so diminishes with distance, but before it does, the area that we are able to view objects in narrows back up – just like a sonar beam narrowing up at deeper water depths. If you were to use the flashlight in an area that was smoky (or poor air quality), you would find that you could not see as far – just like water quality for sonar. Want to see farther? Let’s increase the amount of light that the flashlight produces or its power. Now we can not only see farther but we can also see smaller objects that we could not see before because they did not reflect enough light for us to notice. Light too bright for you or not bright enough to see something that does not reflect a lot of energy? You can partially close or fully open your eyes just like increasing or decreasing the relative sensitivity of a depth sounder. Maybe you are getting a lot of glare? Put some sunglasses on to block some of that unwanted light – much like a filter would work for sonar.

In our products when you adjust the Sensitivity menu setting you are not actually adjusting the receiver gain or the transmitter power. The receivers is basically wide open and all signal level adjustment, filtering other signal processing typically occurs in the computer. So while you may have the sensitivity menu on its lowest setting, the unit is hearing all that it can but only displaying what it is directed to through the unit’s programming. Think of it like this; we assign certain colors (or levels of grayscale) to certain levels of returned sonar signals through programming. Some of these may not even be shown when the sensitivity menu is set to its nominal setting. When you change the sensitivity menu setting, you are changing which color levels relate to which returned sound levels. Each color may now represent more different sound levels (if you turn the sensitivity up) or fewer different sound levels (if you turn the sensitivity down) while at the same time being skewed to either lower or higher sound levels. – Okay, I’ve retyped this like three times and it still sounds like gibberish! It all looks so clear when I draw it out on my white board…

My intention was not to confuse anyone but I feel that I may have done so.

[Cane Pole]

Believe it or not Greg, I understand this stuff. Your answers are clear to me. I see that you use the Tangent function to calculate coverage diameter. I am glad to see that I am not the only one who struggles to explain this stuff. I was hoping you had a Silver Bullet hidden somewhere.

Thanks for the sensitivity lesson. I overlooked the processor possibility as a gain control factor. Now I can “pitch” algorithms as the sensitivity setter. Maybe.

Tom

[Humminbird_Greg]

Thanks Tom. One of those days where everything seemed to be harder than it should be. I struggled with the explanation I gave but am glad that you understood it.

[rockmike]

Do any of you use the SI units in rivers? Does the current distort the imaging.

[Humminbird_Greg]

rockmike, good question. The answer is no, water current does not distort the Si (Side Imaging) sonar. Si is sonar just like the more conventional downwards (or 2D as some are calling it) pointing sonar that many of us are familiar with. Water current does not affect 2D sonar and so will not affect the Si sonar as they both have to obey the same laws of physics - wouldn;t want to get busted for producing a product that breaks the law! What current can do though is interrupt or impede the movement of your boat by either not allowing you to maintain a straight path and/or slowing the speed of the boat. These can distort the Si image. The current can also carry sediment, other water impurities or even objects that will all reflect sonar by some amount. This could make it harder to understand what it is you are seeing on the display of an Si unit but it will not stop the sonar from working.

[gahunter]

I posted before and didn't get a response so I'll try it again and see if anyone will reply with a answer.

With a cost of $2K I was wondering about the length of warranty and how good it is. I'd hate to spend that klnd of money and the unit go belly up in 3 years. Do they offer an extended warranty? For a cost of $2K, I'm not a tournament fisherman so I'd want to be certain I could get at least 10 years
($200/yr) useage if not more. I'd be curious how many years most fishermen get out of their units now.

[ShilohRed]

I posted before and didn't get a response so I'll try it again and see if anyone will reply with a answer.

With a cost of $2K I was wondering about the length of warranty and how good it is. I'd hate to spend that klnd of money and the unit go belly up in 3 years. Do they offer an extended warranty? For a cost of $2K, I'm not a tournament fisherman so I'd want to be certain I could get at least 10 years
($200/yr) useage if not more. I'd be curious how many years most fishermen get out of their units now.

Mine was covered for one year. Could have bought the extended warranty that the place I bought the unit from. but did not.
I think mine should last between 5 and 10 years. I take it off the boat. So its not staying on the boat all the time.
Also if the unit dies in a year or so. I have always had great luck with Humminbird. Not sure if they still have the program. But used to you pay so much and its fixed or replaced.. Looks like the 987c-SI is $249.95 to fix or replace . Yes they mailed me a new unit years back. That hooked me on there customer service. Also that is the reason I did not buy the extended warranty. It was $250..
http://www.humminbird.com/normal.asp?ID=946
Pete