http://www.humminbird.com/Products/798ci-HD-SI-Combo/Display Size - Diagonal:5"
Display Pixel Matrix:640V x 640H
Display Type:Color TFT
Display Colors Grayscale:256 Colors
Sonar Standard:Side Imaging/Down Imaging/DualBeam PLUS
Standard Sonar Coverage:20°, 60° & 180° @ -10db
Standard Sonar Frequency:200/83/455 kHz
Sonar Optional:QuadraBeam PLUS
Target Separation:2.5"
Power Output RMS:500 Watts
Power Output Peak to Peak:4000 Watts
Depth Capability:100 ft (SI/DI), 1500 ft
Temperature:Built In Transducer
Speed:GPS Speed Included
Backlight:Yes
Unit Size - Gimbal Mount:6.9"W x 7.5"H x 4.5"D
Mount A Type:Quick Disconnect
Unit Size - Indash Mount:6.9"W x 5.4"H x 1.25"D
Mounting Options:Quick Disconnect/Optional In-Dash Mounting Kit
Transducer Standard:XNT 9 SI 180 T
Transducer Mounting:Transom
Power Input:10-20 VDC
Power Draw:615 mA
GPS Receiver:Included
GPS Tracking:Included
GPS Chartplotting:Included
Waypoints, Routes, Tracks/Points:2,750, 45, 50/20,000
Humminbird Mapping:Optional
Navionics Gold/HotMaps:Optional
Navionics Platinum+:Not Supported
Platinum Capable:Not Supported
C-Map 4D:Not Supported
360 Imaging:Optional
i-Pilot Link:Optional
HD Radar:Not Supported
NMEA 2000:Optional
5 Port Expansion Module:Optional
WeatherSense:Not Supported
Precision GPS:Included
Heading Sensor GPS:OptionalPC Connect:Optional
External GPS Receiver:Optional
AS Interlink:Not Supported
AIS Compatability:Not Supported
SwitchFire Sonar:Included
Screen Snap Shot:Included
Sonar Recording:Included
Upgradable Internal Software:Included
Split Screen Zoom:Included
Split Screen Bottom Lock:Included
3D Chart View:Included
Large Digits View:Included
Wide/Narrow Cone Split Screen:Included
Custom View Selections:Included
Custom Digital Readout:Included
View Preset Keys:Included
Temperature Graph:Not Supported
Temperature Alarm:Included
Freeze Frame:Included
Instant Image Update:Included
Mark Structure on Sonar:Included
Selective Fish ID+:Included
Real Time Sonar:Included
Triplog:Included
X-Press Menu System:Included
Card Reader Available:Yes
# Card Slots:2
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Bob is correct ... You will need at least 6.570 to recognize the AS GPS HS antenna ...
Rickie