Topband: DC bias tee question

[Pete Smith N4ZR]

I've been looking at the Shared Apex Loop, and one thing I am puzzled by 
(among many) is that the bias tee/DC coupler circuit has both sides of 
the 75-ohm feed coming in from the antenna and the DC supplied to the 
coupler totally isolated from ground, while the ground side of the coax 
going to the receiver is connected to ground.  Having recently been 
totally defeated in building a bias tee of my own for receive antenna 
switching, I wonder if maybe this is a subtlety of the design that had 
escaped me.

Can anyone clear this up? I'll be glad to share the schematic if the 
above isn't enough information.

-- 
73, Pete N4ZR
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