Transducer Angle - Diameter of Coverage

[servocam]

I know your Flasher manual will (should) have this in it, however, if you want to make your own Diameter of Coverage table for your flasher based upon your transducer angle, here is the simple formula to use in a Spreadsheet (or by hand)

By Hand/Calculator: =TAN(ConeAngle) x DepthOfWater
By Spredsheet: =TAN(ConeAngle*PI()/180)*DepthOfWater
Where ConeAngle is you angle of your transducer and DeptofWater is Depth of Water

Solve Diameter of Coverage:
Known: 
Depth of Water = 20 feet
Cone Angle = 10 degrees

Diameter of Coverage = TAN(10) x 20
                                    = 0.176 x 20
                                    = 3.52 feet

Example table I created:


Download XLS file to get you started:   https://docs.google.com/open?id=0B6F9ixuU2UqbNjIwZWUyMzQtZjYwMy00MmU2LWE5ZGQtZjZmNWJmYmQxNWZl

[Fisherman 1]

Nice, I'll have to print that off.  Thanks for the effort.

[Fishrmn]

There ya go.  You're gonna make all of the guys who spent an extra hunnert dollars on their LX-7s mad.  They spent all that money to have their fish finder tell them that.
That is one of the new fangled features that everybody is hyping.
Fishrmn

[jigginPig]

There ya go.  You're gonna make all of the guys who spent an extra hunnert dollars on their LX-7s mad.  They spent all that money to have their fish finder tell them that.
That is one of the new fangled features that everybody is hyping.
Fishrmn

[servocam]

Here, i posted the XLS file - go download and then just modify as needed.  https://docs.google.com/open?id=0B6F9ixuU2UqbNjIwZWUyMzQtZjYwMy00MmU2LWE5ZGQtZjZmNWJmYmQxNWZl

[icontact]

Easiest to remember is about 1 ft coverage for every 3 ft of depth with a 19/20 degree transducer, with a 10 degree of course would be half of that.

[Mudslide]

Yes: but are you aware that there is no industry standard for measuring cone angle? Humminbird measures their cone angle when the signal strength drops to minus 10 DB and Lowrance measures theirs at minus 3 DB. That's a big difference.  Not sure where the others are measuring them.

[JIMC_ND]

Yes: but are you aware that there is no industry standard for measuring cone angle? Humminbird measures their cone angle when the signal strength drops to minus 10 DB and Lowrance measures theirs at minus 3 DB. That's a big difference.  Not sure where the others are measuring them.

Oh, it gets worse than that...    

Just like in the movie "The Matrix" where the kid says "Do not try and bend the spoon. That's impossible. Instead...only try to realize the truth.  There is no spoon."

There is no "cone".

Or at least the "cone" often depicted in diagrams and charts in some of these companies marketing materials. 

That nice and neat diagram where, if a fish is marked on the display in 20' FOW it must within 3.5487 feet of your lure... 

Really?   

The cone angle is actually an arbitrary measurement which relates little to actual sonar performance.

It relates only to coverage in that a "wider" cone angle transducer will of course have a wider coverage area. 

To measure cone angle you must first locate the Peak power point under the center of the transducer. Then you locate the Half Power Point (which is -3dB for Lowrance) on both sides of the peak power point. This is the "cone angle" which is used ONLY to identify the transducer element.

Outside of the Half Power Point in decreasing levels is still usable power. The other half of the total transmit power.

Now the power weakens at an exponential rate the wider the angle, but usable sonar power and useable sonar echoes are received up to 60º on a standard 20º cone angle Lowrance  transducer.

That is why the cone angle is only a measurement to identify the transducer, and does not indicate what will or will not be seen as an echo return.





The better your receiver, the more refined and sensitive it is, working in concert with a good transducer capable of transmitting efficiently and receiving the smallest of return echoes will be able show you sonar detail in a larger area than what the transducers "cone angle" would indicate.

And, oh, what's really going to bake your noodle later on (sticking with "The Matrix" theme here) is this diagram below depicting what sound waves really look like under water with a "20 degree" transducer. 

See the side lobes?

Remember...There is no spoon. 

Jim Carroll NPAA #13

[vtshantyman]

wow thats alot to think about but all good stuff thanks guys

[Gillfisher]

servocam- thank you this will come in handy for an estimated coverage area. Awesome job on the spread sheet.



Jim - good info that most do not realize, how do you determine where the fish are if they are actually in the side lobes? They will show on the flasher at their distance from the transducer letting you think they are actually deeper than what they are. Do those ehcoes show up as weak marks (green on vex) or will they still show up as strong marks?



I think it also depends on your gain setting as well, the gain depending on what you believe is either increasing the power output or increasing the reception of the return signal effectively increasing or decreasing the "cone".

[servocam]

Oh great....we opened the can of worms now.  I was going for the KISS method - Keep It Simple Stupid.     Yes, there is a lot more too it, agreed there.  Just like HiFi and Lasers.  Pull up a chair and have a few...



 

[JIMC_ND]

LOL - My only point was to not get stuck in absolutes with regard to cone angles. 

What you see on your display, and how much area you are actually looking at is very much determined by the quality of your sonar unit.  And not some arbitrary "cone angle".

I use Lowrance HDS units on water and ice. 

I'll never forget seeing for the first time how sensitive an HDS really is on the water.  I dropped a jig over my bowmount trolling motor on a windy day on Lake Sakakawea, and watched the jig drop to the bottom in 60' FOW on the screen. 

OK, I've seen that before, lots of times. 

But what I had never seen before was seeing the jig falling on the HDS display, despite the "crazy" angle my line made in the water as the boat drifted away in the wind.

And I realized in an instant just how much more sensitive the HDS series is over the older Lowrance LCX series sonar (which was excellent sonar BTW).  The broadband digital signal processing in the HDS is the real deal.     

Jim Carroll NPAA #13

[fishlessman]

tan (cone angle/2) x the depth x 2 = cone diameter coverage. you have to start with a right triangle which is half the cone angle, take the tangent and multiply by depth for the radius of coverage, then double it for diameter of coverage on bottom.

[servocam]

tan (cone angle/2) x the depth x 2 = cone diameter coverage. you have to start with a right triangle which is half the cone angle, take the tangent and multiply by depth for the radius of coverage, then double it for diameter of coverage on bottom.

I guess it depends on how the manufacturers define the beam angle.   I didn't think to question when it matched what I found in my Vex manual.  See page 21  http://vexilar.com/pages/support/pdf/vexilar_fl-8slt.pdf.  Mabye you have to use 4.5 degrees in your case (if 9 degree beam)?

[vtshantyman]

I guess it depends on how the manufacturers define the beam angle.   I didn't think to question when it matched what I found in my Vex manual.  See page 21  http://vexilar.com/pages/support/pdf/vexilar_fl-8slt.pdf.  Mabye you have to use 4.5 degrees in your case (if 9 degree beam)?

that explains alot thank you

[MitchMeyers92]

dang you guys, when i got home from fishing the other day i broke out some high school trig and figured out how much bottom i was seeing using some S=O/H C=A/H T=O/A to figure out the distances and angles....when all i had to do was look here! 

[potatomansoup]

Are we really so bored waiting for ice we're doing math and arguing cone angles and bent spoons.... We better get some cold weather soon before we start trying to build flux capacitors to go back to a colder December! Fish Nerds are awesome! Thanks for the information it really is great

[servocam]

Thin ice, no snow, forecast of 40'sthe this weekend.....we are all going

[Gillfisher]

Are we really so bored waiting for ice we're doing math and arguing cone angles and bent spoons.... We better get some cold weather soon before we start trying to build flux capacitors to go back to a colder December! Fish Nerds are awesome! Thanks for the information it really is great

But there is no spoon   

Sorry Matrix fan here as well

[servocam]

But there is no spoon   

Sorry Matrix fan here as well

Well, my last name is Anderson:  As you can see, we've had our eye on you for some time now, Mr. Anderson. (Matrix fan as well)

So, since we are all bored, how about a lecture on harmonic cancellation, or bode plot analysis?

[Gillfisher]

I think I might reorganize my jigs for the umpteenth time instead.   


On a brighter note it looks like it's freezing up again by the house, I may be able to get out again on Sunday 

[vtshantyman]

ok i am down with the flux cap plan it is getting rather stupid now i just want ice