That’s what I was visualizing. This setup would work
100% with a 60 ohm terminator but with a 120 ohm it may
work intermittently. They discontinued making the 60 ohm
and I think I sold mine to Whiskerkev.
You would have to add another tee and another terminator to
meet Lowrance specs..
The antenna would connect to the bottom of one tee and the
520 to the bottom of the other. The terminators would
be placed on each end of the now double tee.
Lowrance also sells a cable with built in 120 ohm terminators on each end.
One end would plug into the unit and the other end to the antenna.
120 ohm In-Line Terminator Cable
Hate to see your GPS quit working when it’s time to find your way off of the lake.