Fishing Victoria Forum

gday all now i will start off by saying i have no idea with sounders of today as my last one was 10 years ago , now the boat i just bought

has a lowrance chirp 5 in it and from matching the picks on the web it looks like i have a 83 200 now what i would like to know is is this

the best one for my use range .

that would be river and estuary so up to 10m for here and when off shore up to 60m in bass strait i also use the down scan function as well

if that makes any difference at all and thats 455khz . TIA

cheers TAC

I have 83/200/455/825khz elite 5 downscan. For the money it is probably the best tinny sounder for around here. The downscan high frequency is good around the lake looking for bait fish and Salmon/ Taylor. it gives a lot finer detail. 200khz is good for offshore snapper fishing.
Unless you intend to start fishing deep water off NSW it will do everything you want.

83 has a bigger cone but not as good resolution as the 200 and is best used in shallow water.
200 is the better one but has a smaller cone but lot better resolution so need deeper water to take advantage of it.


same with 455/800
455 bigger cone cone
800 smaller cone but finer detail

its all about the cone size. google the frequencies and cone sizes for some more info

See if I can explain this clearly. Beam angles on transducers are mostly circular. The angle quoted is worked out by physical measurement representing the point at which the power measured below the transducer is reduced by 6db. So in the middle of the beam X power is measured out at 12deg for a typical small 200khz it would be 6db less.
Who cares? well it makes a lot of difference to the picture you see.
Imagine a typical 2kw 200khz commercial sounder. 5degs. As you travel forward on your vessel and a single fish goes underneath. The narrow beam means. Before you get to the fish you see nothing as it isn't in the beam. Then you get a few pings on it as it passes directly below. Then nothing once you pass it. So on your display you see a single dot. Now imagine there is a bunch of fish. As you pass across them you will see a bunch of dots. Ok do the same thing with a transducer that has 40deg beam. Single fish , BEFORE the boat gets to the fish you will see a dot, as you get closer you will continue to see dots at each ping until it has disappeared out of the beam behind you. But wait there is more. The first ping will be at a longer distance which is represented as lower down on your display. As you approach each ping will be a little closer till you pass over the fish then each ping will be a little further again till the fish is outside the beam. Bingo fish arches. So now a single fish has appeared much bigger than on a narrow beam transducer and is arched. Do the same on a bunch of fish and you get heaps of arches. This is a typical advertising pic. Looks great but really it is telling lies. It shows much more than is really there.
So what about showing the bottom? Well imagine going over 2 rocks close together. If you do it with the 5deg transducer you will see 2 rocks distinctly, with the wide beam you will see one larger rock as the beam will cover both rocks. However because of the arch effect, before you are over the rocks you will see a distinct tail below the normal bottom echo it will arch up to a point when you are over the rock and then back down for another tail as move passed.

Typical Lowrance small sounder beams are 200khz/83khz 20deg and 60deg. 200khz/50khz 12deg 35deg.
The 455khzis not a cone, it is a slice 2.8degx56deg the 825khz is 1.6x32deg. This is done to give you pinpoint discrimination as you move forward, with the wide angle to the side used by the computer to process the bottom shape. i.e it allows for the longer distance, to the sides, and figures a way of presenting it as shapes.

Typical advertising pic. Made by using wide beam angle and travelling slowly over some fish.

If you want to take the "slice" type transducer to it's limits and pay a $200,000, then you can play with something like our work scanning sounder. Slice is 1degx 120deg. It is fed survey quality GPS accurate to 10mm with roll pitch and heave compensation and tide compensation to 20mm.
Then you get this. It has had fish and noise edited out to produce the bottom shape only. Colour is depth.
This is what we survey the bar and channels with.

thanks mike all very useful info and that pic if the ideal beam funnily enough

looks just like the radiation pattern on a 450mhz 20 element yagi right down

to the side lobes .

Yes just in sound instead of electromagnetic.