I have a 700SS in 310 KHz. It is a very good unit, and the resolution is much more useful than any of those low budget models I see mentioned. I use a flat screen monitor and a DAT recorder for playback. For the money, it is outstanding. I have considered selling it, simply because I don't use it often. Seems to me if I decide to get rid of it, I would need $4500.00 or so.
I have also used the more common 107 KHz model, and although the range is much farther, the resolution is just fair, especially on small targets. If you are seeking a large target, the 107 will do what you want it to do once you get good at using it. It takes practice. It will work great in 30 feet of water. But again, it will take some practice to get the pulse length and TVG set to your conditions.
By the way, the e-bay scams also included a stolen set for a bargain price of around $2000.00. I was told the guy was caught, and the sonar was returned to its owner.
If you are looking for a scanning sonar, I have an older Wesmar 150, which uses an 8 inch sound dome I have rigged to hang off the back of the boat. This thing works perfectly, but this is an older set, but it is well built and may last forever. It has never been in salt water. I would take $750.00 for it. This has a round screen and gives a visual like a radar in addition to actual echo sounds (through a speaker). It has very long range potential (1600 feet in any direction), but this is only under really good conditions. I actually detected a large steel wreck in Lake Huron from nearly 2000 feet once. The image showed up as a secondary return. It has range settings from 100-1600 feet. The transducer has tilt and trim, and can be made to rotate 360, in sections or in a straight line. For a big target, this thing will do it's job.
Good luck
Craig
