Author Topic: distance between 800 khz and surface  (Read 2634 times)

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Offline sjefsrafsern

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distance between 800 khz and surface
« on: June 18, 2012, 04:13:45 PM »
hi. im looking for a way to figure out how deep the fish on side imaging is, when im out in the open water. and thougt i might be able to narrow down a little bit by switching between 455 and 800 khz. so my question is: if im  in a place where the lake is 600 feet deep, and got my unit set to 90 feet to eatch side im going to see 180 feet wide and 90 feet deep. (with 455 khz) with the 800 khz i would still see 180 feet wide, but what would be the distance(depth) between what i see and the surface? at 22,5 feet, 45 feet, 67,5 feet and 90 feet of to one side? and will i be able to see the fish as good with the 800 khz as i can with the 455 khz?


stig






Offline sonar2000

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Re: distance between 800 khz and surface
« Reply #1 on: June 18, 2012, 04:38:35 PM »

Offline sjefsrafsern

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Re: distance between 800 khz and surface
« Reply #2 on: June 19, 2012, 12:50:28 AM »
i didnt really understand that, but is it possible to calculate where in the water column the fish are with that? i thougt if i knew the angle between the surface and where my 800 khz starts i could calculate the distance between the surface and my 800 khz beam. so if i see a lot of fish with 455 khz and they ddissappear when i switch to the 800 khz they would sit in the top of the water coulmn where my 800khz doesent "see" them? imight be far out on this one but it kind of makes sense inmy head. :) and its kind of hard to explain what im thinking, and my language skill doesent makein easier... :) and thanks for your reply sonar :)

stig

Offline SonarTRX

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Re: distance between 800 khz and surface
« Reply #3 on: June 19, 2012, 04:48:52 AM »
Hei sjefen (Rafsern),

Det at færre fisk er synlig når du bruker 800 kHz frekvens, istedenfor 455 kHz, er ikke nødvendigvis en sikker indikasjon på at den skjulte fisken ligger høyt i vannsøylen.

Selv om det er forskjeller på deknings vinkelen til siden (mellom 455 og 800 kHz mode), så har jo 800 kHz frekvensen også en mindre deknings-vinkel "front-to-back" slik at færre fisk til enhver tid er innenfor det skarpere 800 kHz lydbildet. (Fisken som dukker opp kan jo også være på dypere vann?)


Tore

Offline sjefsrafsern

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Re: distance between 800 khz and surface
« Reply #4 on: June 19, 2012, 07:13:05 AM »
hei tore, hvis jeg har forstått det riktig så vil ekkoloddet kun vise fisken som står over 30 meter så lenge jeg har satt det til og vise 30 meter til hver side. siden 30 meter ut til siden også er 30 meter nedover, vil vel dette bli en slags zoom som zoomer inn de øverste 30 meterene og de nærmeste 30 meterene ved siden av båten. og hvis jeg da skrur over fra 455 khz til 800 khz og kjører retur på sporloggen min antok jeg at jeg kunne få en indikasjon på hvor dypt jeg bør plasere agnene mine?? :)  og takk for bra svar. :)
mvh stig 


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