Transducers for shallow water

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Anonymous

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I am a commercial salmon troller and we are using a Furuno FCV 1150.
I have a Airmar R99 transducer installed and also two ca50B-9B transducers installed and angled at about 18degrees, one on each side of the Vessel.
The R99 gives great definition, but a lot of the fish we catch and are looking for are at 60 to 180 feet from the surface, and the cone angle is pretty narrow at those depths.
The ca50b-9b gives us a wide view and marks bait well, but It does not give the definition to tell when Salmon are chasing the bait and have it broken and scattered.
Have you tested the new Airmar B275 LH-W ?
I also think that two of the B260s or B265s mounted in tandom should be a better choice than the ca50-9B or maybe just add another R99.
I like being able to change kHz but generally I find that my r99 works best at 52khz and 185.
I know that there are trade offs, What would you recommend to give the best definition and still have decent coverage in the 60 to 180 foot range. Thanks, Kimbo
 
Kimbo,
Yes, we have tested the 275LHW. When you say the R-99 has great definition what frequency are you using, the 52 or 185Khz? Also the term "definition" (like resolution or discrimination) can have a lot of different meanings. Can you clarify what definition means to you?

Snips
 
Snips,
As a example, if I run one ca50b on 50khz, and the R99 on 52khz at the same time,and go over a haystack of herring or other hard bait that has salmon in or around it. The R99 will show the bait as multiple smaller bait schools with hollow centers. The ca50b tends to show the same bait school as a larger soild mass of baitfish.
I have been doing this for 40 seasons (and am still learning) but King / Chinook salmon are very hard to mark and the most consistent way to find them (for me) is to look at the feed pattern. This pattern varies depending on the type of bait and even year to year, but by looking at the sounder when you are getting bites you will begin to see a pattern, and this is what we look for when, the fish are not biting, (are they still here) or traveling/searching for a better spot.
So to sum up, if the R99 is showing me what I am looking for at 200 to 400 feet, is there a transducer that will give me that same look at 200 and up ?
 
Snips,
We fish in a pretty wide variety of conditions and depths. At times the 200 kHz works the best, but when the fish are near the surface the beam angle is so narrow that we don't see enough to get a true picture of what's there.
So maybe the best option would be to add another sounder with two wide beam transducers and run it at the same time as the 1150. Thanks, Kimbo
 
Kimbo,
So are you saying that the R-99 doesn't show you the same fish target separation in shallower water as it does in deep? Target separation is a combination beam width and power. The R-99 is a much better transducer than 50B-9. Below are a couple of screen shots with similar transducers.DSCN0233.JPGDSCN0229.JPG In the second screen shot you can clearly see that the wider beam of the 526T doesn't separate the targets that are close to the fish school.

Snips
 
Snips,
Sorry, I haven't done a very good job of phrasing my question.
The R99 shows me the targets I want to see top to bottom. I would like to see more coverage near the surface. Kimbo


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Kimbo,
There's the rub, to see more off to the sides you will need a wider beam transducer. However the wider the beam, the less side-to-side target separation. The only way around that is to use two R-99's and point them more off to the sides, like you are doing with the 50B-9's.

Snips
 
Snips,
Thanks, that will be a good option provided I can get the existing R99 removed and reinstalled at a angle without damage.
With the 28 degree beam on the 50B-9 I mounted them at a 15 degree angle and it seemed like they had overlapping coverage. What angle should I mount the R99,s at ? Thanks, Kimbo
 
Kimbo,
The R-99 has an LF beam width of 17 degrees which gives you a 60ft foot print at 200ft. If I had to pick an tilt angle I would start at 10 degrees just to see how it worked. I would also see if there were any way I could make the mount with an limited tilt adjustment range.

One thing to be aware of is that you "may" start getting false echoes from the transducers side lobes the more you start tilting them.

Snips
 
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