Is there that much difference in the upgraded transducer and also I mostly fish smaller lakes I live in wv so we don't have real big lakes but what would be the advantages of adding the external antenna
The advantage in the upgrade XHS 9 HDSI 180 T xducer is the added capability of the 800kHz frequency that can be utilized with the 899ci HD SI Combo...
Here is a comparison shot of the 455kHz and the 800kHz...
I use the 455kHz for finding new structure because the image is brighter all the way to the edges of the display ...with the tradeoff of the image being a little fuzzier...
I use the 800kHz to scan closer to structure because the image is more detailed...with the tradeoff of the edges of the image being darker ...
Upgrading to the XHS 9 HDSI 180 T gives this added advantage of scanning closer objects with more detailed and crisper images...
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The AS GPS HS antenna allows the boat icon on the chart views to always show as a boat icon without turning into the round circle...
This allows the user to know which way the boat is pointing on the chart at all times...even while stationary ...
Rickie