View Full Version : Fishfinder Frequencies
Homebrews' Dad
06-30-2001, 02:53 AM
I am wanting to put a second fishfinder on the bow of my boat using a trolling motor mount. I've heard conflicting stories about using the same types of units because of their frequencies. Some say make sure that both units have a different frequency because the will interfere with each other and not work properly, others say hogwash.....
Thanks,
Dave
Dutchman
06-30-2001, 04:16 AM
It's not hogwash, When the cones of the same frequecy transducers overlap vertical lines will appear on the sonar screen. With my LMS 350's this happens at about 16'. You have a choice of running the same frequecy units one at a time to avoid this or have 2 units of differnt frequency's and then you can run them both at the same time. Lowrance was 192khz/50khz,(this is what I use) now its 200khz/50khz. The 50khz does not work as well in shallow water. Pinpoint has addressed this problem with their sonar, I do not know the frequency's they use or if their sonar units are dual band but they do have 2 frequency's they use. You can run any 2 manufactures sonars together as long as they are not the exact same frequency. I used to run a 200khz transducer on the bow and a 192khz on the transom wirhout any difficulty whatsoever. Hope this helps....
Bass & Walleye Boats has done a couple of articles on this subject within the last year. They recommend a minimum 40 khz frequency seperation. The problem is that most units operate in the 200khz range. Lowrance has a 50 khz module that can be used but it was designed for deep water applications, not shallow. Pinpoint has a system that does a 40 khz spread between units but it applies ONLY if you purchase thier trolling motor also. The stand-alone unit for the stern still operates at 200 khz. The unit associated with the bow trolling motor operates at 240 khz.
The only unit that I have seen that operates outside of the 200 khz range is made by Vexilar. I believe it is called The Edge and is a dual freq. unit that operates normally at about 100khz or 400 khz. This seems like a great idea. The down side is that their market and support does not exist out West.
mlc