HDS 200 khz vs 83 khz

[mississipi]

I see that a lot of folks like 83khz better than the 200khz. I understand the cone angles and area covered by each.  I usually run mine on 200 but understand I am missing some coverage but gaining some detail. But if you are looking for stripers does detail matter?  If you mark fish while on 83 kHz and the fish are deep how without sidescan would you know if the fish are left, right or under you?  Hope these are not too stupid of questions. Any thoughts appreciated!

[Deleted]

Great question. A mark on the screen at say 20 foot can be anywhere as long as it is in the cone. The bigger the cone, the less the clue you have at where the fish is. For example, pretend the cone covers all of the water. A mark at 20 foot could be 20 feet below you or 20 feet in front of you on the surface. My point here is that as the cone angle increases the less clue you have of actual depth. Thus, I like 200 for jigging because there is a better chance that my spoon is actually in the strike zone and that the fish are directly under my boat. However, 83 is nice because it tells you that fish are around and gives you hope. The more marks, the more chance I might be in a good area to fish. Keyword.... Area!

Then there is side scan which can definitely help show you where the mark is relative to your boat. But just like my example above, side scan does a crappy job of indicating depth unless you throw a net out right next to your boat. Additionally, many marks are in front or in back of you and even side scan can't help.

So... It's all an approximation. The only thing that I know for certain is if my screen is lit up on 200, I'm a happy man!

[Deleted]

You really got me thinking. Probably because I have your same questions all the time and don't spend enough time with them. But since you asked, I am now motivated to clear this up for myself. DANGIT!

Anyway, if 83khz equals around 60 degrees cone angle and 200khz equals around 20 degrees, then this means that the diameter of the circle on the bottom is aproximately 1 times the depth for 83 and 1/3 times the depth for 200.

So let's say I am searching for bait in 10 feet of water. I see a nice school of bait to my right on side scan. I turn on it and and my tm transducer is set to 200. Much to my surprise, my tm does not see the bait. What?

Bottom line, my transducer is only covering around a 3 foot circle by the time it hits the bottom. And this circle is only 1.5 feet at 5 foot of depth. No wonder I couldn't see the bait.

Put it on 83 and my circle of coverage is now 10 foot on the bottom.

Thus at 10 feet of water, 83 seems like the best if your throwing a net. Or, you could do what the wise folks do and turn off your electronics and throw on blips.

Play this game with various scenarios in your mind and you start to understand the value of a spilt screen that shows both 200 and 83.

Now let's say you see a mark at 40 foot. With 83khz,this mark could be anywhere from 40 foot directly below your boat TO as shallow as 35 foot 20 foot away in any direction. Much uncertainty.

If you see this same mark on 200khz, this mark is anywhere from 40 foot directly below your boat TO as shallow as 39.5 feet 7 foot away in any direction. Certainty.

Conclusion, 200 kHz is the sweet spot or bullseye of 83khz.

For very shallow water, 200 doesn't see much.

For deeper water, if I'm jigging, I need marks in my 200 cone or I'm lying to myself. However, if I am pulling bait, then 83 kHz is probably your best bet.

Ahhh.... I feel better.

[mississipi]

Thanks, Very good explanation! I have always kept mine on 200 but think I'll try 83 while idling around looking for fish then if lucky enough to find them, switch to 200. mwardncsu and I had a little discussion about this and I think we are on the same page.

[Pete D.]

That's why I was so intrigued with chirp. If I set my unit to medium chirp I get just about the wide come angle of 83khz and the resolution of 200khz. Is it necessary, no. But I sure appreciate it. The airmar TM150 has superb resolution, even when running it directly into a non chirp lowrance unit. I'll post some screenshots when I get a chance.