Humminbird Side Imaging Forums

Other Interest => DIY - Side Scan Sonar and towfish => Topic started by: Rickard on May 29, 2010, 05:31:27 AM

Title: Scanning at 262 and 455 kHz
Post by: Rickard on May 29, 2010, 05:31:27 AM
time for 265 kHz as well
hendirk

Yes Hendrik, we shouldn't forget about the 265 kHz option (or is it 262?) in the old SI transducer. Unfortunately, I have the HDSI transducer permanently mounted to my towfish, and I have my SI transducer hull mounted, so I can't test the SI transducer with the towfish. But, this winter I used the SI transducer for sector scanning under ice and made some comparisons between 265 and 455 kHz. I used two 10 m HB original extensions, if I recall correctly. Anyway, the 360 degree scans shown below are obtained at 265 and 455 kHz, respectively. Depth from the transducer is 5.5 m (16 ft) and range (radius) is 50 m (150 ft). Both images are transformed from rectangular to circular with slant range correction (the water column is thus eliminated). What you see are some 80 years old concrete barges close the Stensborg island outside the city of Luleå in Sweden. To me they tell that the 265 kHz frequency can be very useful in some situations. Perhaps it's much better than 800 and 455 kHz in a towfish application with long cable?

Sector scan at 265 kHz.
[attachment=1]


Sector scan at 455 kHz.
[attachment=2]
Title: Re: Scanning at 262 and 455 kHz
Post by: Jolly Roger on May 29, 2010, 05:39:09 AM
Wow Rickard,
these pictures are amazing! Congratulations!

Regards / Harry
Title: Re: Scanning at 262 and 455 kHz
Post by: sonar2000 on May 29, 2010, 07:59:00 AM
Nice slant range.   I guess the transducer must be moving and not stationary???????

Chuck
Title: Re: Scanning at 262 and 455 kHz
Post by: Rickard on May 29, 2010, 08:57:39 AM
Chuck,

The transducer is rotated at a stationary position (a hole through the ice). Last year there was a long discussion on this method here: http://www.xumba.scholleco.com/viewtopic.php?t=851&postdays=0&postorder=asc&start=30 (http://www.xumba.scholleco.com/viewtopic.php?t=851&postdays=0&postorder=asc&start=30)

Rickard
Title: Re: Scanning at 262 and 455 kHz
Post by: abraquelebout on May 29, 2010, 10:50:53 AM
nice images, i hope that the 255 khz and 455 for  more width, and 455 - 800 for detail
in 455 there 35 m left and right in 800 khz no more than 15 meters
today bad weather, more wind and waves... the sea is not ok for test :'(
the towfish is now conected at 55 metres of clear signal cable...i'm waithing better condition
Title: Re: Scanning at 262 and 455 kHz
Post by: sonar2000 on May 29, 2010, 02:55:20 PM
thanks, Rickard.  I had not thought of this.  good picture...
Chuck
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