Looking for a little insight, any help appreciated.
I'm considering either the new Lowrance Mark 5 or Mark 5 Pro for an inexpensive bow finder for my aluminum boat.
Other than power (this I understand fairly well) the main difference for the extra $$$ is the transducer frequencies and cone angles.
One is a 200kHz, 60 deg. the other a dual frequency 83/200kHz, up to 120 deg. angle.
I understand the effect of cone angle given a depth of water, but can anyone fill me in on the dual frequency systems, what the accomplish, and the advantages/disadvantages?
Thanks all
Transducer Frequency/Cone Angle Question
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The Captain
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eye-tracker
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Re: Transducer Frequency/Cone Angle Question
The easiest way to explain the advantage of dual frequency is if you are using one unit on your transom and another on the bow. With the rear transducer working at 200kHz and your front one working 83kHz you will get no cross talk or interference. Often when I am fishing at the bow my fishing partner will watch the back sonar as we are working structure, so this is a huge advantage of having two sonars on at the same time.The Captain wrote:Looking for a little insight, any help appreciated.
I'm considering either the new Lowrance Mark 5 or Mark 5 Pro for an inexpensive bow finder for my aluminum boat.
Other than power (this I understand fairly well) the main difference for the extra $$$ is the transducer frequencies and cone angles.
One is a 200kHz, 60 deg. the other a dual frequency 83/200kHz, up to 120 deg. angle.
I understand the effect of cone angle given a depth of water, but can anyone fill me in on the dual frequency systems, what the accomplish, and the advantages/disadvantages?
Thanks all
-sheldon
Sheldon Hatch
Just a guy that likes to fish walleye
Just a guy that likes to fish walleye
The answer to your dual frequency question varies or the type of fishfinder.
On some you have the option of choosing one or the other frequency. The wide beam marks fish further out but has less definition.
On my Hummingbird PiranhaMax 170 the 200kHz (20 deg) works all the time. Only when the Fish ID+ is turned on does the 83 kHz (60 deg) show information. When both are working the narrow beam fish show as a solid black & the wide beam fish show as an outlined fish indicating fish further to the side. Very seldom do I use this feature. I prefer to see my fish as arches or as lines when stationary, instead of fish symbols.
On some you have the option of choosing one or the other frequency. The wide beam marks fish further out but has less definition.
On my Hummingbird PiranhaMax 170 the 200kHz (20 deg) works all the time. Only when the Fish ID+ is turned on does the 83 kHz (60 deg) show information. When both are working the narrow beam fish show as a solid black & the wide beam fish show as an outlined fish indicating fish further to the side. Very seldom do I use this feature. I prefer to see my fish as arches or as lines when stationary, instead of fish symbols.
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West Lake Willows
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As sheldon said the dual frequency is nice if you are trying to run two units off separate transducers. You will also find the low frequency usually has a wider cone angle and although will penetrate deeper it gives less detail. The best analogy I have heard to explain this is sound.
A low frequency is like bass, it travels further but without a lot of definition. So you hear the bass of a car in the distance long before you hear the higher more detailed treble. So a lower frequency will penetrate deeper but doesn't have the detail of a higher frequency.
Something to consider with the cone angle is if you are bottom fisherman of fish a lot of structure a really wide cone may not be best for you as it will average the bottom. So with a 99 deg transducer (the calculator I am using is found here http://www.furunousa.com/LearningCenter ... lator.aspx and only takes up to a 99 deg cone) in 20 fow would cover 47 feet of bottom which is great if looking for fish but it averages the 47 feet of bottom it is viewing to give you one line on your sonar screen so it isn't going to be real accurate. Where as a 6 deg cone would see 2 feet of bottom so searching for fish in 20 fow would be almost useless, but you get a very accurate picture of bottom. Does this make sense?
One of the things guys do with a dual frequency transducer is run a split screen with one side on the wide angle cone and the other on narrow cone. This way you can search for both fish and see bottom structure. You can also tell if the fish is right under you or out to the sides if you see fish on the wide angle and not the narrow cone. Where as if you see the fish in both you know it is right under your boat. Works great.
Scott
A low frequency is like bass, it travels further but without a lot of definition. So you hear the bass of a car in the distance long before you hear the higher more detailed treble. So a lower frequency will penetrate deeper but doesn't have the detail of a higher frequency.
Something to consider with the cone angle is if you are bottom fisherman of fish a lot of structure a really wide cone may not be best for you as it will average the bottom. So with a 99 deg transducer (the calculator I am using is found here http://www.furunousa.com/LearningCenter ... lator.aspx and only takes up to a 99 deg cone) in 20 fow would cover 47 feet of bottom which is great if looking for fish but it averages the 47 feet of bottom it is viewing to give you one line on your sonar screen so it isn't going to be real accurate. Where as a 6 deg cone would see 2 feet of bottom so searching for fish in 20 fow would be almost useless, but you get a very accurate picture of bottom. Does this make sense?
One of the things guys do with a dual frequency transducer is run a split screen with one side on the wide angle cone and the other on narrow cone. This way you can search for both fish and see bottom structure. You can also tell if the fish is right under you or out to the sides if you see fish on the wide angle and not the narrow cone. Where as if you see the fish in both you know it is right under your boat. Works great.
Scott
Last edited by West Lake Willows on Sat Jan 23, 2010 8:56 am, edited 1 time in total.
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The Captain
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West Lake Willows; Thanks for the link to the Transducer-Beam-Angle-Calculator. 
The reason I went to the Hummingbird over the Eagle was the transducer angles. The Eagle's 60 & 120 deg angles seemed too high for my purposes compared to the Hummingbird's 20 & 60 deg set-up.
The calculator won't even calculate angles over 99 degs. By my calculations on a 120 deg transducer in 100' of water the bottom area covered would larger in diameter than the length of a football field or aprox. 350'.
On my Hummingbird & on Eagle units I researched the high frequency is the narrow beam to give better definition below the boat. Not sure which is most common though. Usually Lowrance & Eagles use similar set-ups but as the unit The Captain is inquiring about is new not all info is easily available.West Lake Willows wrote: You will also find the low frequency usually has a more narrow cone angle,
Scott
The reason I went to the Hummingbird over the Eagle was the transducer angles. The Eagle's 60 & 120 deg angles seemed too high for my purposes compared to the Hummingbird's 20 & 60 deg set-up.
The calculator won't even calculate angles over 99 degs. By my calculations on a 120 deg transducer in 100' of water the bottom area covered would larger in diameter than the length of a football field or aprox. 350'.
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West Lake Willows
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Woodsman,
Sorry, reading over that, not sure why I switched them. Your right, the higher frequency usually has the more narrow beam. Anyway, thank you for catching that.
I didn't really look for info regarding the unit Captain is looking for, but it does seem like a crazy wide angle transducer. It would seem that it is designed to search for bait and or fish in shallower water. So for a bowmount it might be a great idea as you are usually casting shallower water from the bow. It may not be your best option for finding and staying tight to weedlines though.
If you get it Captain, give us a review on it.
Scott
Sorry, reading over that, not sure why I switched them. Your right, the higher frequency usually has the more narrow beam. Anyway, thank you for catching that.
I didn't really look for info regarding the unit Captain is looking for, but it does seem like a crazy wide angle transducer. It would seem that it is designed to search for bait and or fish in shallower water. So for a bowmount it might be a great idea as you are usually casting shallower water from the bow. It may not be your best option for finding and staying tight to weedlines though.
If you get it Captain, give us a review on it.
Scott
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The Captain
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West Lake Willows
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Captain,
In thinking a little bit more about such a wide angle transducer, it may be really good at staying on the edge of a weed bed. If you are in say 15fow your cone diameter would be somewhere between 55 and 60 feet. with you being in the center you would be seeing about 30feet out to the side. If you are able to see the weedline from 30feet away as you approach it you could cast to the weed line before you are overtop of it.
It would almost work as a side scan and you could see that you are approaching it, instead of being overtop of it like a 20 deg would do.
Still not sure how it would show humps and bumps, I don't think it could as your unit would be averaging an area of 2827 square feet.( in 20 fow with a 60 foot diameter cone) to return a single line on your screen. I think humps and bumps would be non-existent. Something to ask the rep if you care about bottom strucucture.
Just my thoughts. I am in the process of adding a new sonar unit to my boat that is why I am so interested.
Scott
In thinking a little bit more about such a wide angle transducer, it may be really good at staying on the edge of a weed bed. If you are in say 15fow your cone diameter would be somewhere between 55 and 60 feet. with you being in the center you would be seeing about 30feet out to the side. If you are able to see the weedline from 30feet away as you approach it you could cast to the weed line before you are overtop of it.
It would almost work as a side scan and you could see that you are approaching it, instead of being overtop of it like a 20 deg would do.
Still not sure how it would show humps and bumps, I don't think it could as your unit would be averaging an area of 2827 square feet.( in 20 fow with a 60 foot diameter cone) to return a single line on your screen. I think humps and bumps would be non-existent. Something to ask the rep if you care about bottom strucucture.
Just my thoughts. I am in the process of adding a new sonar unit to my boat that is why I am so interested.
Scott
Scott: Just a couple of minor math corrections to start.
A 120 deg. cone at 15' = aprox. 42.5' dia. of coverage.
20' = aprox. 70' dia. of coverage.
Picture a transducer as a piece of pie. Transducer at the point & shortest route to bottom at the middle of the curved section. As you progress away from the center point you will have dead spots along the bottom as these points will be further away from the transducer than the bottom your marking.(Sometimes marks below bottom may indicate things in dead zone) The wider the transducer cone the larger this dead zone is.
On a 120 deg. transducer at the edge of the transducer cone aprox. 1/2 the water depth will be in this dead zone. Objects at the edge of the cone will also appear much deeper than they are. In this case objects @ 7.5 fow would appear on bottom.
At times this same principle accounts for it looking like fishing raising to your lure when actually they were at the same level just moving closer to the center of the cone. With colour or greyscale finders you can at times tell this is happening when the fish contact becomes more strong as get gets higher on the screen.
Hope this helps; Rick
A 120 deg. cone at 15' = aprox. 42.5' dia. of coverage.
20' = aprox. 70' dia. of coverage.
Picture a transducer as a piece of pie. Transducer at the point & shortest route to bottom at the middle of the curved section. As you progress away from the center point you will have dead spots along the bottom as these points will be further away from the transducer than the bottom your marking.(Sometimes marks below bottom may indicate things in dead zone) The wider the transducer cone the larger this dead zone is.
On a 120 deg. transducer at the edge of the transducer cone aprox. 1/2 the water depth will be in this dead zone. Objects at the edge of the cone will also appear much deeper than they are. In this case objects @ 7.5 fow would appear on bottom.
At times this same principle accounts for it looking like fishing raising to your lure when actually they were at the same level just moving closer to the center of the cone. With colour or greyscale finders you can at times tell this is happening when the fish contact becomes more strong as get gets higher on the screen.
Hope this helps; Rick
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West Lake Willows
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Rick,
What did you use to do the cone calculation? I was using the Furuno calculator that as mentioned doesn't allow an angle to be inputted over 99 deg. I just estimated by entering 99 deg then 21 deg and estimated the total cone size. I should have looked for a calculator that would take 120 deg before posting, I'm sure there are lots out there. Sorry for posting an estimate, but thank you for the accurate number.
The piece of pie analogy works and gets the point across, but I think a more accurate comparison would be an ice cream cone upside down as it is more conical, course all transducers aren't cones, some are elliptical as well.
The concept that makes dead zones is the same concept that makes stationary fish appear as "arcs" on your graph. As the boat travels over the fish it is marked in the front of the cone. As the boat moves directly over the fish it appears closer to the boat that it was at front of the cone, then as the boat goes by the fish it is again marked at the back of the cone and shows it is deeper or farther from the boat. Hence an arc on your graph.
I don't want to come across as pretending to know everything about electronics, in fact I would say in the grand scheme of things I know very little. I am interested in electronics and I think, for the most part freshwater fisherman vastly underestimate the ability of electronics. Although, this is probably because we primarily fish with cheap electronics. Most salt water guys spend more time choosing the transducer or just as much time as they do the head unit. We just use the cheap stock transducers. I have heard it said that using the stock transducer with a high end unit is like putting rabbit ears on an HD tv. It really chokes the ability of the head unit.
Its cool to see guys on here that are interested in the transducer and how it will apply to their style of fishing. I think that is rare in our area. Woodsman, you have a very good understanding of the technology, do you work in the industry or just researched it for your own use?
Scott
What did you use to do the cone calculation? I was using the Furuno calculator that as mentioned doesn't allow an angle to be inputted over 99 deg. I just estimated by entering 99 deg then 21 deg and estimated the total cone size. I should have looked for a calculator that would take 120 deg before posting, I'm sure there are lots out there. Sorry for posting an estimate, but thank you for the accurate number.
The piece of pie analogy works and gets the point across, but I think a more accurate comparison would be an ice cream cone upside down as it is more conical, course all transducers aren't cones, some are elliptical as well.
The concept that makes dead zones is the same concept that makes stationary fish appear as "arcs" on your graph. As the boat travels over the fish it is marked in the front of the cone. As the boat moves directly over the fish it appears closer to the boat that it was at front of the cone, then as the boat goes by the fish it is again marked at the back of the cone and shows it is deeper or farther from the boat. Hence an arc on your graph.
I don't want to come across as pretending to know everything about electronics, in fact I would say in the grand scheme of things I know very little. I am interested in electronics and I think, for the most part freshwater fisherman vastly underestimate the ability of electronics. Although, this is probably because we primarily fish with cheap electronics. Most salt water guys spend more time choosing the transducer or just as much time as they do the head unit. We just use the cheap stock transducers. I have heard it said that using the stock transducer with a high end unit is like putting rabbit ears on an HD tv. It really chokes the ability of the head unit.
Its cool to see guys on here that are interested in the transducer and how it will apply to their style of fishing. I think that is rare in our area. Woodsman, you have a very good understanding of the technology, do you work in the industry or just researched it for your own use?
Scott
A piece of paper, a protractor & a vernier. Before seeing the calculator my calculations were dead on for 60 degs. and only very slightly off for 20 degs. That's the reason for the "aprox.".West Lake Willows wrote:Rick,
What did you use to do the cone calculation? I was using the Furuno calculator that as mentioned doesn't allow an angle to be inputted over 99 deg.
Agreed but not as simple to explain.The piece of pie analogy works and gets the point across, but I think a more accurate comparison would be an ice cream cone upside down as it is more conical, course all transducers aren't cones, some are elliptical as well.
A combination of much research & an understanding of mathematics and a little electronics.Woodsman, you have a very good understanding of the technology, do you work in the industry or just researched it for your own use?
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West Lake Willows
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LOL..and I thought it would be an internet calculator. Sad how dependent our society has become on electronics.Woodsman wrote:A piece of paper, a protractor & a vernier. Before seeing the calculator my calculations were dead on for 60 degs. and only very slightly off for 20 degs. That's the reason for the "aprox.".West Lake Willows wrote:Rick,
What did you use to do the cone calculation? I was using the Furuno calculator that as mentioned doesn't allow an angle to be inputted over 99 deg.
Of course the old timer fisherman would probably say the saying thing about what this post is all about.
I have learned a lot in the last few weeks regarding this subject from talking to Gameco the wholesaler for airmar. Very knowledgeable guys over there. I still have lots to learn and looking forward to a new setup this summer that should be much better then what I have been using which is a shoot thru 50/200 khz 600w lowrance transducer. I got a new boat just before the season last year and got everything except a thru-hull transducer done so I just used a shoot thru to see how it would do. It wasn't that great.
This past fall Sheldon would take screen shots of his unit when I was beside him. My screen shots would have a bait ball but not defined and I would not mark hooks around the bait. Sheldon's was a much clearer image with clear hooks around the bait. His was a transom mount ducer. I was told I would lose some sensitivity going thru the hull, but that I would be ok because I had a good head unit (LCX 113C). Yeah....that....wasn't...true lol
. So I'm going to keep my 113C and the shoot thru transducer (I'll run it on 50khz) but mainly use the screen as a chartplotter. I'm going to install a second screen (furuno fcv585) and a thru hull transducer 1kw 200khz, 25deg (airmar SS264). It will be a better transducer then I have ever used and I'm very much looking forward to the salmon and late fall walleye season, as it will "see" much more then I was seeing last season.BTW I have looked local, but can't buy the SS264 local so buying from www.toptransducers.com there is a live chat feature on this website that is awesome. The owner is David very helpful and knowledgeable guy.
Scott
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eye-tracker
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Just to add some more information... be very careful with wide angle transducers if you fish structure. As a walleye angler I am often working structure and you need to understand Dead Zones and the limits of a transducer. The wider the cone the more the dead zone.
The other information you need to understand is the side lobe and actual shape of the transducer cone you are using.
-s
The other information you need to understand is the side lobe and actual shape of the transducer cone you are using.
-s
Sheldon Hatch
Just a guy that likes to fish walleye
Just a guy that likes to fish walleye
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West Lake Willows
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