 Definitely One for PBraffitt
I think it’s best that I explain the differences between the two models and let you decide which will suit your fishing style the best. The B744V offers depth, speed and temperature output. It will only handle 600 watts of input power, which is more than acceptable for your application. The 50kHz beam width is 45 degrees and the 200kHz is 12 degrees. The wide beams are an asset in shallower water but won’t display structure as clearly or detailed as a narrow beam will. The B744V transducer has a “Q” of 28 and 31 (at 50 and 200). I have attached an article that was published in our newsletter a while back and should explain “Q”.
The 256 series is manufactured using four of the same elements used in the above B744V, but all four ceramic elements are wired together so they act as one large element. This gives the 256 series 16 times the sensitivity of a single ceramic model such as the B744V, and the ability to handle 1000 watts of input power. The beam at 50kHz is 14 x 23 degrees, and 3 x 5 degrees at 200kHz. Both beams are elliptical since the four elements form a football shaped pattern. The “Q” factor are 21 and 30 (50/200).
Basically the 256 series will give you more detail of fine structure due to its narrower beams. It will show much more detail of suspended targets such as bait schools and fish close to the bottom, where the single element model will tend to “blend” targets together or into the bottom image. The 256 will also allow you to output 1000 watts, which won’t really help you in the shallow environment. The B744V will give you a broader view of what is around the boat due to its wider beams, but you won’t be able to tell you where they are any better than the B256.
If you don't mind a narrower beam than the 256 you may want to consider the 260 series. They are very serious performers with \"Q\" factors of 8 and 10 (50 and 200) and beam widths of 19 degrees at 50 and 6 degrees at 200. The detail on the screen would be awesome, but you would spend more time trolling due to the narow beams.
The \"Quality\" Factor:
Measuring the Sharpness of a Transducer's Response
We all know the term horsepower as a measure of engine performance, stereo output is measured in decibels, and knot expresses boat speed. But what term is used to describe the performance of a transducer? It’s Quality Factor or Q. More specifically, Q measures the sharpness of a transducer’s response. A transducer with a low Q will allow a sounder to display sharp images.
To understand Q, you must understand a little about how transducers work. When an electrical pulse from an echosounder is applied to a transducer, the element inside begins to vibrate. This vibration sends sound waves through the water under the boat. This is much like the vibration of a bell after it is struck.
You know that a bell continues to ring for a time. Likewise a transducer will continue to vibrate after an electrical pulse has been applied. This phenomenon is known as ringing and is indirectly measured by Q. Unfortunately while a transducer is ringing, it cannot receive a clear echo. Thus ringing reduces the clarity of images on an echosounder screen. And it keeps a transducer from \"seeing\" in very shallow water.
It is important that the element inside a transducer stop ringing as quickly as possible. In other words, the goal of a good transducer is a sharp sound wave that stops quickly followed by \"listening\" for an echo. We say such a transducer has low ringing. Ringing cannot be totally eliminated, but with the proper engineering it can be greatly reduced. Airmar designs its transducers to dampen vibration quickly.
The lower the Q, the less ringing a transducer displays. Factors range between 1 and 40. A Q factor of 10 or less is considered low. Compared to our competitors' transducers operating at the same frequency, Airmar transducers have a lower Q, thus less ringing. All things being equal, a sounder coupled with an Airmar transducer will display sharper images.
Happy Holidays!!
Peter Braffitt
Business Development Manager
AIRMAR Technology Corp.
Milford, NH USA | 
