Seiwa Si-Tex MDA2 - Manual (Page 15)

Installation
Page 12
Step 2 - Connecting the VHF antenna
Route the cable from the VHF antenna to the AIS receiver and connect to the VHF connector on the AIS receiver as shown in Figure 7.
A standard marine band VHF antenna or AIS antenna should be used with the AIS receiver. The connector type on the AIS receiver is
SO239. Your chosen VHF antenna requires a PL259 connector to mate with this. If your VHF antenna does not use this type of
connector please contact your dealer for details of available adaptors.
Figure 7 Position of the VHF antenna connector
Power and data
NMEA 2000
VHF antenna