800kHz

[Radar19871]

Does anybody run their DI or SI on 800kHz with good results?

I can't seem to get a good picture running 800kHz, I have messed with every setting I can. It would seem the Higher frequency would give more detailed returns, but it seems to not be picking up even large timber on 800kHz. I am not happy with the SI on my GT52 at all (join the club I know) the DI seems to do OK but there is much to be desired there as well.

Running 7612 with GT52 btw.

[puhlw]

I think mine gets a better image on 455 and I fish clean shallow freshwater. Go figure. Mine is a GT30 though.

[coachallen]

I thought 455khz was for shallow water? I am wrong? I have been running 455 because I fish shallow.

[puhlw]

Typically you get more range with 455 so better for deep water or longer range. Tradeoff is you loose some detail. (In theory).

[Radar19871]

I have the exact same results as you puhlw....i'd just like to know why the theory is not a reality. If I turn the brightness to high on 800 it just clutters up too much. But if I lower to remove clutter I get almost no returns.

[puhlw]

I have found mine works the best on 455 with stock settings except I have to turn the TVG setting to high or I get a lot of noise on side imaging.

[Larry3215]

Im still trying to decide if this might be the reason - Garmin tilted the DI elements on all the GT transducers 16 degrees to port. Im pretty sure that also tilted the 2D to port because (I think) they use the same elements for 2D and DI.

http://www.bbcboards.net/showthread.php?t=824839

They have admitted it causes some "shadowing effects" but I dont know what that means for sure.

I have the same issues you guys do with my GT51. It makes better DI and SI images on 260 than it does on 455 - which goes against the theory. It should be just the opposite. The GT51 does not do 800.

[Riccochet]

I'll have to do some tests. I've only ran my GT52 on 800 Khz. Maybe I'll get out a little tomorrow and see what's what.

[LWINCHESTER2]

Garmin tilted the DI elements on all the GT transducers 16 degrees to port. Im pretty sure that also tilted the 2D to port because (I think) they use the same elements for 2D and DI

I'm pretty sure that is not correct. In the literature on the lawsuit Garmin mentions three different configurations of transducers. Tilted element, shaded array and stepped array. All the specifics are not identified as far as which transducer uses which technology except GT-20 is mentioned with the tilt design and the GT21 is referred to as the shaded design. In the same context as the GT21 the GT22 and GT30 are mentioned but it does not say what design they are. I think it is reasonable to figure that some of the GT transducers may not be tilted, shaded array or stepped array transducers.

Also considering the beam patterns and chirp frequencies of the 2d along with the low "Q" I think it near impossible for a long narrow rectangular element to produce such a 2d result. Because of that I would conclude that the 2d comes from a separate element just for 2d.

I have found 800 kHz on Garmin to be a great performer. Some better on the GT50 than on the GT52 but the GT52 is no slouch. Of course I am not looking for structure detail, just fish.

[Larry3215]

I think you're right about the 2D element Leonard, but I think the "shaded array" you are talking about is different from the "shadowing effect" Troy's secrete informant is talking about. Here is the quote from the secrete agent:

The current production GT downvu transducers use a 3-pc Downward array that is rotated to port side 16degrees. Provides a bit of shadowing effect without affecting depth performance.
on the go

[GetReel]

Both my Garmins and my Lowrances produce better detail on 455... but I am usually 25' or less..... never over 40'