Can someone explain Lowrance dual frequency transducers

[drbrand]

All I can find for Lowrance dual frequency transducers are 50-200khz and the HDS units are 83/200khz. I think there is shred of info that I don't know. Do the HDS units use a 200khz transducer for both 83/200khz frequencies?

[LWinches]

Apparently the 50/200 actually has two transducer elements, one for 50 and one for 200.

Borrowing from Humminbird, as they have been doing this for years, it possible to use a single 200 kHz transducer element, vary the signal to it and get a wider cone at 83 kHz. So it is not a new transducer. The HDS has the electronics to broadcast at 83 kHz through the Lowrance existing 200 kHz element.

Not only did they borrow from Hbird, they improved on it. My experience is that the HDS 83 kHz performs better (meaning deeper) than Hbird. Hbird 83 works down to 50-60 ft. HDS works down to 90-100 ft. I don't really know why but I speculate that the reason for the improvement is that on the HDS you can set it to 83 kHz only and them jack up the ping speed. You can't do that on the Hbird.

[3M TA3]

Perhaps this will help you out Doc. http://www.lowrance.com/Support/Tips...nsducer-Guide/ The sonar tutorial on the same page will help you out also, I'm sure.

[drbrand]

I knew that I was missing something with how the dual frequencies worked. Thank you very much!

[1625rebel]

Not trying to hijack (seems to have been answered), but which frequency do most people use in fishing shorelines down to say 30 feet or so?

I usually use the 200 khz because the narrower cone angle gives me a better representation of how I fish. Which is a lot of contour trolling where the depth drops from 12 feet to 24 feet rather quickly. If I used the 83 khz with 35 degree cone, I would roughly triple the size of my area on the bottom and would probably display shallower than I actually was? Also I like knowing that if I see fish on the display I can be reasonably be sure they are right under my boat.

I do see better fish arches with the 83 khz and of course see more fish returns as well (triple the area). I think that with the 200 and narrow cone I see some fish that are half in the cone and half not, thus the issue with sometimes now showing arches very well. Positives and negatives to both. What are peoples thoughts and actual practices here?

[3M TA3]

Originally Posted by 1625rebel

Not trying to hijack (seems to have been answered), but which frequency do most people use in fishing shorelines down to say 30 feet or so?

I usually use the 200 khz because the narrower cone angle gives me a better representation of how I fish. Which is a lot of contour trolling where the depth drops from 12 feet to 24 feet rather quickly. If I used the 83 khz with 35 degree cone, I would roughly triple the size of my area on the bottom and would probably display shallower than I actually was? Also I like knowing that if I see fish on the display I can be reasonably be sure they are right under my boat.

I do see better fish arches with the 83 khz and of course see more fish returns as well (triple the area). I think that with the 200 and narrow cone I see some fish that are half in the cone and half not, thus the issue with sometimes now showing arches very well. Positives and negatives to both. What are peoples thoughts and actual practices here?

What do you mean when you say you see better arches with the 83 KHz vs the 200 KHz. Are the tops of the arch flatter. They should be with the 83 because they're (the fish) in the cone longer however since you are covering more area with it you should see more arches representing fish and those fish further out will have sharper peaks and will be smaller because they aren't in the "cone" as long. The trouble with the 83, in my opinion, is that it is harder to estimate the depth of the fish the further they are away from the center of the cone. Remember, an arch at 20 feet in say 30 feet of water doesn't necessarily mean the fish is at 20 feet deep. It only means the fish is 20 feet from the puck. Big difference. Arch shape is everything to me.

[1625rebel]

I get partial arches for some of the 200 khz fish (missing the front or back of the arch). I figured they were partially in the cone, but I could be off base with that one. I have tilted the transducer a couple of times to find the sweet spot (initially it was tilted too far forward).

The 83 Khz arches are usually fully developed from front to back with a very pronounced and classic arch. I do mark more fish from the larger coverage. Good point about the exact depth. Also didn't know about the sharper peaks meaning they were further out.

[walleye.bill]

I actually prefer the dual frequency because in most of my presentattions I am covering a large amount of water if trolling long lines even we use 12ft poles plus 8 ft apart that is a 32 ft spread. With dual frequency the width you mark is equal to your depth. With the single cone 1/3 of your depth. Therefore I am seeing what I am fishing with the larger area

[3M TA3]

Originally Posted by walleye.bill

I actually prefer the dual frequency because in most of my presentattions I am covering a large amount of water if trolling long lines even we use 12ft poles plus 8 ft apart that is a 32 ft spread. With dual frequency the width you mark is equal to your depth. With the single cone 1/3 of your depth. Therefore I am seeing what I am fishing with the larger area

Actually Bill on a 20 degree puck you are seeing way more than 1/3 of your depth. A 20 degree puck only means that by design, 20 degrees is the 3db power (half power) point. Also, just a note, the widest dual frequency puck I've seen is 37 degrees although I have heard of some 60's. Your dual frequency unit is, I am guessing, 37 degrees. That equats to about 75% of your depth at 3db. I am positive that your sonar can "see" out to 6db which would be 150% of your depth with a 37 degree puck. 2 1/2 cents.

[walleye.bill]

Actually I run a Humminbird 997 SI and I run it on dual beam which is a 20/60 which as advertised is coverage equal to your depth. Should have mentioned I am not using a Lowrance. This is also where I get the 1/3 of your depth. 20 degrees is a 1/3 of 60 degrees therefore it would be safe to assume you see a 1/3 of your depth if you see equal coverage to depth at 60 degrees. Don't know I could be wrong but it is what I've been told and whats advertised on the humminbird website.


Here is a video
http://www.youtube.com/watch?v=17zMA...layer_embedded