Author Topic: Image Frequency  (Read 4703 times)

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Offline Dieago

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Image Frequency
« on: January 29, 2014, 07:11:54 PM »
What is a instance you would want to use 800 instead of 455 and 455 instead of 800? If you never scanned over 60' would it be better to leave on 800? I was looking through menus and thought to myself Its on 455 and Ive never tried it on 800 ever.
I'm trying to think, but nothing happens!


Offline Bob B

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Re: Image Frequency
« Reply #1 on: January 29, 2014, 07:57:08 PM »
800Khz is better for clarity and 455 is better for SI range and better sensitivity.  You could find something on 455 and switch to 800 to go back and take a better look at it.

If you are always using a fairly narrow range....you should try out the 800Khz.....I'd probably still leave it on 455 for general scanning.
**Looking for the one that makes it all worthwhile**

Offline rnvinc

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Re: Image Frequency
« Reply #2 on: January 29, 2014, 08:42:04 PM »
Here's a frequency comparison I did for a seminar...

*455kHz brighter out to the edges of the screen ...but fuzzier...
*800kHz darker out to the edges of the screen...but crisper...

I use 455kHz when searching for new structure ...the brighter image makes it easier to see structure out to the edge of the display...

I use 800kHz when my boat is closer to "on top" of structure...the crisper image makes it easier to define details of the structure...



Rickie
« Last Edit: January 29, 2014, 08:43:38 PM by rnvinc »

Offline Dieago

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Re: Image Frequency
« Reply #3 on: January 29, 2014, 08:47:45 PM »
Thanks this helps. Would I be better to leave it in 800 then if lets say in 15-20' water and si range less than 60' ? or does the outter edges stay dark no matter the range? Also if main objective was searching for fish?
« Last Edit: January 29, 2014, 08:52:52 PM by Dieago »
I'm trying to think, but nothing happens!

Offline rnvinc

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Re: Image Frequency
« Reply #4 on: January 29, 2014, 10:26:36 PM »
Depth and SI Range are just part of the equation...

Bottom composition will have a big effect on how bright the image will be...

A hard bottom will reflect sound very well...so a lower Sensitivity can be used to garner an acceptable image...(this shot was at about 12 SI Sensitivity)..



A soft bottom will absorb sound...so a higher Sensitivity may be needed to garner an acceptable image..(this shot was at 19 SI Sensitivity and the edges were still dark)...



As I mentioned before...

When I'm looking for new structure...I want to be able to descern the entire display ...so I will run 455kHz to brighten the image...(and use SI Sensitivity to adjust the 455kHz brightness)..

Then when I see something interesting to the side...I drop a waypoint on it...

Then I will reposition the boat to pass closer to the structure while using 800kHz to descern the details of the structure....(and use SI Sensitivity to adjust the 800kHz brightness)...

Rickie

BTW...even tho I use 455kHz about 50% of the time on the water...I post very few 455kHz images...because the 800kHz makes much prettier images to post into the forums...


« Last Edit: January 29, 2014, 10:49:40 PM by rnvinc »

Offline rnvinc

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Re: Image Frequency
« Reply #5 on: January 29, 2014, 10:34:37 PM »
I forgot to address your question about searching for fish...

If the fish species you are searching for are bottom fish like in the orange image above...800kHz works fine for that...

But if you are searching for suspended fish out to the sides...the 455kHz is going to be the best tool...because the 455kHz beam angle reaches all the way to the surface out to the side ...(while the 800kHz beam angle only reaches part of the way to the surface-missing fish suspended higher than the 800kHz beam angle can reach)...



Frequency choices are tools..each with certain attributes...

*Frequency beam shape should be used as a tool depending on what part of the underwater world one is targeting...(the target has to be in the beam shape or it's not going to show on the display)...

*Frequency clarity should be used as a tool depending on the detail needed..(do I want to see it out at the edge of the display-455kHz... or do I want to see the details of it closer to the boat-800kHz...?)

I would hope no one limit the capabilities of the unit's available tools by using only 1 frequency....

Frequency choices (455kHz vs 800kHz) are very important tools...used for very distinct different tasks....

Rickie
« Last Edit: January 29, 2014, 11:08:51 PM by rnvinc »

Offline Dieago

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Re: Image Frequency
« Reply #6 on: January 29, 2014, 10:55:14 PM »
Oh! I get it the si freq also determines wide and narrow cone angle just like in 2d. Thanks!
I'm trying to think, but nothing happens!

Offline rnvinc

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Re: Image Frequency
« Reply #7 on: January 29, 2014, 11:10:17 PM »
Oh! I get it the si freq also determines wide and narrow cone angle just like in 2d. Thanks!

Your getting it now...(even tho the SI beam shapes are fan shaped slices and not cones like 2d...you still have the concept now)...

Use each frequency for what it does best...

Rickie
« Last Edit: January 29, 2014, 11:18:21 PM by rnvinc »

Offline rnvinc

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Re: Image Frequency
« Reply #8 on: January 29, 2014, 11:14:39 PM »
Your getting it now...

Use each frequency for what it does best...

Rickie

I just wish HB would put the frequency setting in the SI Xpress menu...(where I wouldn't have to go all the way into the Sonar tab to change it...oh well...)

Rickie


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