Ultimately, you could go and aimlessly troll the ocean without knowing what’s underneath you and you might get lucky, but let’s face it, in the time poor world most of us live in, we need everything working for us. And whilst luck is a big part of fishing, getting lucky is a combination of time on the water and level of effort applied to fishing in the most likely areas. To help with this we need our transducer to be the clearest and strongest set of underwater eyes possible. Then we need to be able to understand what it’s showing us. Like most things these days, technology is moving so fast, with side scanning, down scanning, chirping, 3D scanning and so on. Many of us struggle to keep up, or just add it to the “too hard basket”. I get that, but it’s a shame. If you took just a small amount of time to understand the basics, you can really improve your success rates. To help explain the black magic that is a transducer, I’ll break this article into a few sections. I’ll explain the positions they can be installed, the features of different types of transducers and even some of the crazy acronyms used to describes different models of transducers. TM / TH / PM...
Yep, even before you try to work out what you need, the first thing most get stumbled by is the way transducer manufactures describe their mounting design. Let’s touch on that first. TM, stands for “transom mount”. With these you screw them to the outside of the transom, this is probably the most commonly encountered and sold transducer. With these you get the most amount of flexibility when it comes to picking the ideal spot on the transom to install it. They come in a range of shapes and sizes. TH, stands for “through hull”. With this guy you’re generally drilling a big scary hole through the bottom of your boat. The outside of the transducer face is in contact with the water and the inside sealed from the outside with a big washer and a nut. These are pretty neat and well suited to higher speed applications or hull’s that don’t have the space for transom mounted transducers. They’re also less prone to bottom breaks in rougher conditions due to them being on the underside of your hull, thus in the water more than some transom mounts. Naturally you only get one go at getting these in the right position. It really pays to do your research before you let loose with that 90mm hole saw and tube of Sikaf lex. PM, stands for “pocket mount”. These are similar to a through hull transducer where the outside face is in contact with the water, however these are most commonly built/ moulded into the hull so they sit perfectly flush with the bottom of the hull. Again they do everything a through hull can do, only a little better due to their f lush finish and some other reasons we will touch on down a bit further. If you aren’t an experienced shipwright, these are best left to someone that knows there way around fibreglass! WHAT’S THE GO WITH WATTS? There is such a huge array of output power options available. Navigating this and getting past some of the old school ways of thinking is a mind field on its own. With improvements in sounder performance, along with it has come the ability to read deeper and clearer than ever before. There was a time that if you wanted to see the bottom over the continental shelf, say 150m+ with any real clarity, you needed a 1kW (1000watt) transducer. If you wanted to see 500m+ fishos were using 2 or 3kW transducers! If you haven’t seen the physical size of a 1kW transducer, then imagine a house brick and you’re close. While a 3kw, well picture something more like a brief case! They are huge, and in a trailer boat, very difficult to find somewhere to install them.. I’ve been fortunate enough to partake in some Garmin Marine product testing and have seen first hand the improvements in fish finder and transducer performance. These days we have more technology in our mobile phone than the NASA engineers had in their computers when they sent the first man to the moon. Similarly things have got smaller and more efficient with marine electronics. And it’s the same with transducers. On my boat today I have a few transducers, including a couple of 1kW units. However due to the power output and additional features of my lowest power transducer I find myself using that more than the larger units. If you’re fishing in nothing over a couple hundred meters, chances are today’s modern 500-600 watt transducers will more than adequately do the job without needing to go the expense and hassles of using a 1kW or higher powered transducer. If, on the other hand, you want to look at the bottom in depths over 200m+ in high levels of detail, then yep, you’re going to want a 1kW transducer. Seldom do we see the need for any more power than 1kW. Again this is due to the improved technology from both the transducers and their respective head units and modules. THE LOW DOWN ON FREQUENCIES Here is another area you’ll need to get right when selecting your transducer. Once you’ve decided on the power output the next thing you need to consider is what you actually want to see. Now I know you’re all saying... well I want to see fish and I want to see bait. However, where in the water column do those target fish hang out? If you’re a bottom angler you’re going to want a frequency that provides good detail of fish on or near to the bottom. On the other hand if you’re a game fishos your target species tend to be found in the upper water column so your transducer needs to read closer to the boat and ideally have a beam width that covers a larger amount of water under the boat. If you’re an estuary fisho you might be more interested in looking for and analysing structure. This is where you’d look at using side and down scanning type transducers. With most transducers these days, the higher the frequency the more detail they return to your screen. However, at the loss to depth and distance capability. This is where it’s important you understand what you’ll be doing with your transducer. Let’s focus on the commonly available frequencies in traditional sonar. Low Frequency or Low Chirp is best used for those wanting to fish in very deep water. This might be the fisho that wants to drop for deep sea fishes, such as bar cod, gem fish and those chasing swordfish. The 1kW variants, depending on the output capability of the sounder where it’s connected has the ability to read bottom in 1000m. The beam width of Low Chirps are pretty wide too so they cover a good amount of the water column, however at speed they can be difficult to get a clear sounder screen due to the low frequency and wider beam width. Medium Frequency or Medium Chirp is very common these days. It’s a very good middle ground between low and high chirp. It has a good beam width, slightly less than low and more than high. It performs very well in both shallow and deeper water. In 1kW down to around 500m I’ve found it especially good during the tuna season. It seems to mark them up very well. In the same breath I’ve also had great performance from it fishing the bottom for species like snapper and kingfish. High Frequency or High Chirp commonly comes in two different configurations, a “narrow” and a “wide beam”. If you’re a dedicated bottom fisho you’ll get the best result from the narrow beam high chirp. Its narrow beam provides very good clarity, target separation and ensures that what you are seeing on your screen is very near the boat. They also perform very well at speed due to the narrow beam not seeing much of the interference boat hulls produce. The wide beam chirp is all the rage today, particularly in the game fishing scene, and rightfully so. It has both great clarity, but with its wide beam covers the most amount of the water column ensuring you are seeing as much as you can around the boat. The other bonus here is when a pelagic fish swims through the beam. Due to it being so wide, you see a big, long arch or squiggle line across your screen making the presence of that fish very noticeable. These High Chirp narrow and wide beam transducers can read down to around 200m quite reliably in a 1kW variant. Advances in technology Coming back to the advancements in technology, today’s transducers are capable of so much. Companies such as Garmin and Furuno both have transducers that can look “forward” providing a massive advantage to modern sport fishing boats. Garmin also offers transducers that provide a “real time” return. Its known as Panoptix; much like an ultrasound scan of your wife’s baby, you actually see fish swimming under the boat, or even more excitingly swimming up to your bait or lure. You can actually watch their reaction to the lure. It’s about as close as it gets to an underwater camera! It’s important at this point to mention that when you are seeing fish on your traditional sonar screen, everything other than a tiny bit at the right of the screen is “history”. They have passed your boat and depending on the depth and speed you and the fish are travelling at could be quite some distance behind you! This Garmin all seeing Panoptix sonar is “real time”, not historical. If you’re seeing it on the screen the fish is under your boat right at that time, it’s pretty incredible technology. Similarly we have some amazing transducers providing down and side scanning sonar. These transducers return images much like a photo. If you drive over a tree, you literally see a tree, drive over rocks, you see rocks, a bridge you see a bridge. I’m sure you get the idea. Some of the more powerful side scanning transducers have the capability to scan 300m of the bottom either side of your boat. Just imagine how much of an advantage that is to have when you are searching new ground or looking for fish holding up on a reef or around structure. Better still, when the beam passes over a fish, you see the shape of a fish! Whilst the side and down scanning transducers have been primarily embraced by the bream and bass fishos, with the availability of more powerful transducers now offshore fishos are turning to them to help find bait and larger fish. Speaking from personal experience, I use mine all the time to find bait when marlin fishing. I’ve been amazed how many times I’ve had a lifeless traditional sonar screen only to notice the side scan has picked up bait ball on the left or right of the boat, which would have gone unseen if I hadn’t been using that transducer. At the end of the day as it was explained to me, regardless how good a transducer you have, its only as good as the location it is installed and how well suited it is to your hull. Its like owning the best ultra-high definition television. If the TV antenna you have connected to it isn’t pointing in the right direction you won’t get a clear picture. The same goes for transducers. Take the time to understand how transducers work, find the right location, or better still, consult someone with experience with transducer installation before you cut your hole or screw it off to the transom. Get that right and you will have terrific success and catch a lot more fish and have a lot more fun. More here: upscaleexistence blog
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