Transducer angle

[rmitchel]

I am wondering what you think about the following:

Last spring, while at Cabela's, I was in the market for a new fish locator. I wanted a Garmin 160 with speed. The sales person suggested the Garmin Blue -- two transducer setting and the speed was included. Well I jumped on it.

But now in relation to a new trolling motor and corresponding fish locator the issue of transducer angle came up (see recent threads).

From these posts and e-mails with Garmin, I learned that a transom transducer is primarily 20 degrees and a trolling motor transducer is often 15 degrees.

I also learned that Blue series in the Garmin line is primarily marketed as a salt water model. With this in mind, the dual transducer for the Blue model is 45 degrees and 15 degrees.

I am wondering what you think of this. Any thoughts? Is this a good thing or not so good of a thing in freshwater (shallower depths)? I can do the math and understand the differences in the view.

In an earlier post, I referred to my fish locator as a "lying fish locator" -- never really sure if what I was seeing were fish. Well, perhaps such a wide angle contributed to this.

Trying to decide if I should buy a 20 degree transducer for the Garmin 160 that I have.

Bewildered.

Thanks.

[Thom]

Rick,

Let me say this before I go on, I have a dual frequency sounder and I need one for the type of fishing I do but my use is an awful lot different than your's is.

The salesperson should never have suggested to you that the 50 kHz side of the transducer would be of much value to you. It won't be. The 50 is great for shooting into deep water, and that is particularly important if the water happens to be salt, but you get that deep water penitration at a cost, and that cost is picture resolution. Simply put you won't get anywhere near the picture with a 50 as you will with a 200. There's not much reason to say any more about it than that other than this, you won't have any need for a 50 unless you regularly operate in water greater than about 250 feet deep. I don't even switch mine over until 250-300 feet and sometime not until much deeper. So with the only real advantage of the lower frequency transducer being its ability to penetrate deeper, but having the double drawbacks of having much worse target discrimination along with a very wide area of coverage it is simply a shame that the salesperson would have suggested one to you for shallow water operation.

As to the 15 degree cone angle vs. the 20 degree cone angel, the point is moot. The cone angle does not define what you can and can not see. That is one of the nastiest myths going. All the cone angle defines is the half power (-3dB) point. It is a convienent way to compare different transducer options but there is absolutly nothing on this earth that says that what your machine is capable of picking up and displaying is restricted by that angle. Simply put some machines have such poor sensitivity that they can't register stuff that is inside of the half power cone and some are so well made that they can easily 'see' targets that are outside of the same imaginary cone.

I wish this board was set up so I could see your original post while I'm trying to reply, because I know there is more to an good answer for you than you got here, but I just can't remember all that you asked. I do know this, I have seen some very knowledgable persons give some very good advice on this board but I have also seen some very bad advice given out here, some of it selfserving, so be careful about what you pay attention to.

Thom

[KP]

I have a dual frequency sonar but I'm not familiar with your Garmin. On mine, both frequencies operate out of one transducer. I frequently use the 50KHz (45 degree cone angle) in shallow water (6-50 feet) while moving at higher speeds and looking for specific structure. The wider angle helps me find that structure quicker. It also will mark fish but not as accurately as the narrower angle cone. After I find an area that may hold fish or mark fish, I switch over to 200KHz (20 degree cone angle) to get a better look at whats below.

I wouldn't say the salesman did you wrong, but you don't need dual frequency for shallow water fishing. I wanted that wider angle as long as it would work in shallow water. The manufacturer said it would and it does.

[Hooky]

Thom is right. I also purchased the 160 Blue from Reeds Sports and after reading up on it, it was no use to me. They were kind enough to trade in in for the 160 Red. The dual transducer is of no use unless you fish deeper than 200-250 feet of water. Good Luck

[Gumbo]

Thom, I wish you'd expound more on the cone angle subject, as I always just thought in simple terms--20 degree cone, etc.

As for seeing the messaging you're replying to, just click "Reply with Quote" rather than just "Reply". The original message will appear as shown below.


>Rick,
>
>Let me say this before I go on, I have a dual frequency
>sounder and I need one for the type of fishing I do but my
>use is an awful lot different than your's is.
>
>The salesperson should never have suggested to you that the
>50 kHz side of the transducer would be of much value to you.
> It won't be. The 50 is great for shooting into deep water,
>and that is particularly important if the water happens to
>be salt, but you get that deep water penitration at a cost,
>and that cost is picture resolution. Simply put you won't
>get anywhere near the picture with a 50 as you will with a
>200. There's not much reason to say any more about it than
>that other than this, you won't have any need for a 50
>unless you regularly operate in water greater than about 250
>feet deep. I don't even switch mine over until 250-300 feet
>and sometime not until much deeper. So with the only real
>advantage of the lower frequency transducer being its
>ability to penetrate deeper, but having the double drawbacks
>of having much worse target discrimination along with a very
>wide area of coverage it is simply a shame that the
>salesperson would have suggested one to you for shallow
>water operation.
>
>As to the 15 degree cone angle vs. the 20 degree cone angel,
> the point is moot. The cone angle does not define what you
>can and can not see. That is one of the nastiest myths
>going. All the cone angle defines is the half power (-3dB)
>point. It is a convienent way to compare different
>transducer options but there is absolutly nothing on this
>earth that says that what your machine is capable of picking
>up and displaying is restricted by that angle. Simply put
>some machines have such poor sensitivity that they can't
>register stuff that is inside of the half power cone and
>some are so well made that they can easily 'see' targets
>that are outside of the same imaginary cone.
>
>I wish this board was set up so I could see your original
>post while I'm trying to reply, because I know there is more
>to an good answer for you than you got here, but I just
>can't remember all that you asked. I do know this, I have
>seen some very knowledgable persons give some very good
>advice on this board but I have also seen some very bad
>advice given out here, some of it selfserving, so be careful
>about what you pay attention to.
>
>Thom