Sonar Frequency for Trolling?

[MarkNY]

i have a lowrance HDS on my boat and last year i had it set on 200KHZ for the whole season. i put downriggers on the boat this year and noticed that i can only mark my downrigger weights when i have it set to the 83KHZ. i havent been marking alot of fish or bait so far this year so i dont know how the 83 freq. will perform. is it important to mark your downrigger weights when fishing? what frequency is best for trolling or does it depend on what type of fishing your doing? ie: shallow or deep etc. just looking for tips on how to make the best use of my sonar. thanks, mark

[Chromeslayer]

lots of good info here

http://www.thehulltruth.com/marine-elec ... under.html