Author Topic: scaning in 455 than 800 khz  (Read 3337 times)

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Offline abraquelebout

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scaning in 455 than 800 khz
« on: June 11, 2011, 07:07:03 PM »
2 days scaning in salt wather over  30 m, towfish with 60 m cable
i thing that scaning in salt water is possible in 455 khz but difficult in 800 because in 800 a little wave or interference make a very bad picture, problem with current to take the target in 8 or 10 meter range
i join sampleila_rendered in 455 khz, good picture
[ Specified attachment is not available ]
in 800 khz there's more noise (wave, motor...) the picture is not good
800 khz is very nice in river
i hope that a double ducer in 455 khz is a good solution in salt water...
as anybody get experience in this type of search


Offline abraquelebout

  • volunteer rescue diver, surfer, publicist
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  • Accessories: towfish lowbird /LSS2-hdsi, 60mcable
Re: scaning in 455 than 800 khz
« Reply #1 on: June 11, 2011, 07:08:51 PM »
picture in 455ila_rendered

Offline Rickard

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Re: scaning in 455 than 800 khz
« Reply #2 on: June 12, 2011, 05:28:33 AM »
Hi Abra,

Interesting to see your experiences. I seems as if waves is the main issue when scanning at sea. I mostly scan in lakes and in the Baltic where conditions are rather easy to cope with (some days conditions are terrible, though..).

When I see your results I recall having seen systems where the towfish is almost boyant and towed 10 - 20 m behind a heavy depressor. Waves which affect the boat will affect the depressor, but the effect on the towfish will be small. Perhaps this would enhance the results more than a doubleducer would?

Regards,
Rickard

Offline abraquelebout

  • volunteer rescue diver, surfer, publicist
  • Sr. Member
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  • Joined: Apr 2010
  • Location: france
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  • Unit(s): 898, 1198, helix G2
  • Software: deep,,drdepht,reef.
  • Accessories: towfish lowbird /LSS2-hdsi, 60mcable
Re: scaning in 455 than 800 khz
« Reply #3 on: June 12, 2011, 07:42:50 AM »
ok rickard
i think making a eavy profiled lest 15 m behind towfish (5 kg seem's a good solution)
towfish 5,7 kg an 5 kg lest i hope that it may be working...
i test it and publy result...

Offline Rickard

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Re: scaning in 455 than 800 khz
« Reply #4 on: June 12, 2011, 08:09:51 AM »
Abra,

Here you have one among many examples of how this can be arranged.
http://www.openseas.com/stabs-tow.htm
They say a neutrally boyant towfish is ideal.

Rickard



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