Transducer Differences- Marking Baitfish While Salmon Trolling on Lake Michigan

Airmar SS175HW vs Simrad TotalScan- Transducer Comparison for Great Lakes Salmon Trolling

I posted a Salmon Trolling Report for Ludington (Lake Michigan) recently on FaceBook and got a lot of questions about the marks on my sonar screen. Turns out a lot of salmon trollers haven't seen what a dedicated high-power CHIRP transducer can do for target separation- so here's my real-world comparison.

The Skimmer Experience 

Most anglers are running standard skimmer transducers and bait shows up as a 'cloud' of pixels.  The transducer can't differentiate where one bait ends and another begins...so it 'paints' them as one big blob. 

The Simrad Totalscan is a capable transducer but it's made to do 3-4 jobs: Sidescan, Downscan, standard echo (83/200khz), and med/high CHIRP. The echo/CHIRP ceramic is located at the front of the housing, so it's relatively small...I would guess no more than roughly 2 inches in diameter based on the housing size.  It runs at 300W for med/high CHIRP. 

Sidenote:  I also fought cavitation constantly with the skimmer at trolling speed- tweaked the installation repeatedly and never fully solved it. High speed readings were consistently dirty...usually no return fish/bait at all.

The Airmar SS175HW

The Airmar SS175HW is a dedicated CHIRP transducer- that's its only job. At roughly 4.5 inches in diameter and 1,000W it's a beast compared to the TotalScan. Dedicated, tuned ceramics focused on one task rather than four.  Tho my head unit is only capable of 600W I believe.  Still twice the power.

After installation (I had to cut a hole in my boat!...bleh☹️) the improvement was immediately obvious- no lengthy tuning period, no cavitation issues at speed, fantastic clarity and target separation.  Now most of this clarity is due to reduced cavitation/bubbles which is pretty much inherent if you mount in a clean area (clean water) unobstructed thru-hull....btw.

The Comparison

Both screenshots below are from my Simrad GO12 set to high CHIRP at similar water depths:

LEFT- 300W Simrad TotalScan, transom mounted: separates the top few feet of bait reasonably well, then turns to cloudy mush below.

RIGHT- 1000W Airmar SS175HW, thru-hull mounted: individual hooks all the way through the water column.

Same head unit. Different transducer. The improvement is hard to argue with.

Bottom Line

If you're serious about finding suspended bait, marking fish cleanly, and differentiating fish from each other on the Great Lakes, a dedicated high-power CHIRP transducer is worth considering. The Totalscan is a solid all-around unit but I think it's a compromise.

One honest disclaimer- it's possible I never fully optimized my TotalScan settings. If you've had different results with a skimmer setup I'd genuinely like to hear about it.  Also the images were at different times, so maybe the bait was piled in tighter in the skimmer pic?  But I seldom ever see any clumps like I used to with the skimmer.  If I do, they are usually by the bottom.

Tech Specs Gleaned from the Web:

Simrad, TotalScan, 300W: 

Medium CHIRP: 67-100 kHz, 60deg
High CHIRP: 167-233 kHz, 20deg

Airmar, 175HW, 1000W:

CHIRP: 150-250kHz, 25deg

And ANOTHER disclaimer:  I ain't no engineer...wait...actually I am...a retired engineer.  But I'm no TRANSDUCER engineer.  So the size difference I mention betwix the skimmer/Airmar could be a few things that I don't really understand.  I know there is a Piezo ceramic element in there and some copper.  I believe the ceramic is 'tuned'...either thru design or electronics.  So the larger size of the Airmar could be several things...multiple ceramic elements?  Larger Ceramic?  Electronics for tuning/refining signal?  All of those?  Dunno.

So a lot of what's posted above are my own observations, guesses, ponderings, speculations and lessons learned by time on the water...and more than a few phone calls to tech support!