One of them will suffice ... they can be programmed in "split frequency" mpde, where it will receive on 440 and transmit on 2M.... a pair of FT-817ND's ...
It's on page 45 on my FT-817 manual. But if you're using software to program your '817s, it's even easier to do.
With its single antenna lead from its duplexer, it's a great antenna for the '817!... an Arrow II antenna with duplexer on the way ...
Which one did you choose? Have you "double-checked" its readings with, say, the AMSAT site? Or Heavens-Above.com? Or, for AO-51, I have a live tracking widget for AO-51 at ...... satellite tracking app on my iPod touch ...
You've got the "satellite bug," Ed!