On the antenna, I suggest you contact Lowrance and give them your antenna
specifics. The antenna the 2000c comes with is an amplified unit.

I did some checking and found that the answer is apparently no. The
Lowrance external antenna runs on 3 - 3.3V and has a gain of 8 - 10
dB, whereas the antenna
I use with my Garmin can run on 4 - 24V and has a gain of 26 - 31 dB.
My Garmin puts out 5.8V on the antenna connector center pin with no
load. The Lowrance uses a type MCX connector, whereas the Garmin uses
a BNC. There are some non-Lowrance external antennas available that
will work with the 2000C, but those that I have found are "mouse"
style intended for use on the glareshield (vs mounted on the exterior
of the aircraft).

David Johnson