said by gunther_01:The loco can use both chains while using an external and one internal antenna. The external one must be horizontal. And I found this in most cases to work lousy if one chain had good signal and one had a bad signal. Simply using the external antenna exclusively worked better.
I thought the 900Mhz loco used both chains while in external antenna mode. Or at least the option is there to use both, albeit with different signal strengths on the chains because of it