Yellowfin Sidescan Sonar

[Gonyo]

Blurry

Just nicer pics.

[Rickard]

Specs

Don't know if it helps but the -3 dB beam width at 455 kHz in the Humminbird SI (the older one) transducer is about 1.4 - 1.5 degrees. That can be computet from the length of the transducer. Imaginex, on their hand, don't tell at which dB-level they specify the beam width. It's probably the conventional -3 dB level. In all, the systems seem to perform about equally well with respect to resolution limits caused by beam widths. -3 dB is just an indication figure. Sounder systems' displays seem to show intensity levels down to about -10 dB which corresponds to a much wider beam. Moreover, dB-figures refer to transmitted energy. When transmitted sound comes back as an echo it is formed once more into a narrower beam as compared to when it was transmitted. In the end it's what you see on the display that counts.

Rickard

[Clart]

I posted this elsewhere so apologies if you've read it twice.

Another modification suggested to me by two people who should know about these things (equipment hire and sales people) is the use of a 'depressor wing' for supposed deep tow and stability.

It's a wing shape, sort of looks a bit like a Stingray, but made of lead and attaches to the tow cable in front of the fish. The idea is it sinks the fish and prevents the fish from rolling and yawing by damping the cable ahead of the fish.

I've yet to try it but should be able to report back within a month how it goes. My gut feeling is a preference for the body modification mentioned earlier in the thread ie to go for an extended body filled with lead and i'll be trying that out also as I have two Yellowfin to play with.

Has anybody else tried this method?