GNS 430 reception problems

Hi,

I'm looking for folks that might have a similar experience. Recently
upgraded the panel to include a GNS 430 and replace one of those old
NARCO all in one VOR instruments plus an old NARCO radio.

Anyway great upgrade. The GPS function works wonderfully. Filing /g is
the best. The NAV function works great. Dual glide slope indicators(the
other is slaved to a KX-155) really makes IFR manageable.

The problem is the COM function of the GNS 430. We're only getting about
40 miles of range on the receive side of the COM. I'll call for flight
following on COM1(the GNS) and never get an RX indication. When I flip
over to COM2 (the KX-155) it works just fine. The KX has a range of at
least 80 miles. The GNS seems uneven. We can xmit and be heard over
distances but the receive side is really only useful in and about the
terminal area. This is less than optimal.

When we did the upgrade we kept the original antennas that were on the
plane(PA28-180).

Our avionics guy is baffled, maybe useless at this point. He swapped out
the GNS plus ran a myriad of other tests. He says everything is checking
out just fine. But that is surely not our experiences. So I turn it over
to the collective wisdom of the net. Has anyone else ever experienced
anything similar?

Thanks.