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Modulting transducer beam width?

Old 03-21-2007, 12:09 PM
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Default Modulting transducer beam width?

It is possible to use the settings of a depth sounder head unit to modulate the beam width of a transducer?

This question occurred to me as I was looking at a comparison of transducer technical data from the Airmar technical data catalog. I was comparing the beam patterns of a B60 and a B258 and noticed that there are specific beam widths listed for a given dB level. Let's compare the 200 kHz frequencies. (B258 has two numbers because it is a an oblong mulit-element array)

Beamwidth in degrees

B258
-3dB 3 x 5
-6dB 5 x 7
-10dB 7 x 10


B60
-3dB 11
-6dB 16
-10dB 21

Those dB numbers look to me suspiciouly like gain. There's a gain setting on most fishfinders, so by adjusting the gain can you also adjust the beam width? If I could dial the dB back to -10, I'd have a beam width closer to the B60 unit.

I'm interested in this from the perspective of creating a wider beam in shallow water. With the pencil-thin beam of the B258, you can only see a tiny little spot under the boat in the typically shallow water I boat and fish in. I'd love the use a 1 kW 'ducer for the resolution but also need the beam width of a 600 W unit. It looks like both the tilted SS164 and the new wide-beam unit Airmar is developing is going to be out too late to be any good to me this season, so my options look to be a B60-20 or a B258.

Anyone?
Old 03-21-2007, 12:31 PM
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Default Re: Modulting transducer beam width?

That a interesting question. When I went though the set up on the Simrad CX44-E you can change the unit for fresh or salt water. What it changes I really cant remember but it does make a difference.
I know the change has to do with the salinty in the salt water....Mark
Old 03-23-2007, 09:07 AM
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Default Re: Modulting transducer beam width?

Anyone... someone's got have an inkling, or is this just nuts?
Old 03-26-2007, 05:01 PM
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Default Re: Modulting transducer beam width?

I got the answer from Airmar today: no. I guess it was too much to hope for.

The over all beam pattern of a ceramic cannot be changed. The dB readings on the tech data are not relating to gain on the sounder but rather they are particular sections of the pattern.
They suggested I wait for the SS270W - it'll have a 25 degree beam at 200 kW. The question for me is availability. Aimar's answer on that:
It originally was coming in the spring but it's looking more and more like Summer 2007. Samples need to be sent out to our OEM customers, the OEM then tests and qualify the new product. At that point production should start.
I won't hold my breath since it requires lots of outside companies to test and get back to them.

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