The ADL RP-3 would be the best choice for accurate setting of
the polarity/skew. It had the original patent for C/Ku reception,
which the Chaparral Corotor II infringed upon. If it were possible
to show you a Corotor II from about 10 years ago versus one made
and sold recently, you would notice a mechanical difference in the
Ku probe. After a patent infringement settlement, to avoid future
payment of additional royalties, the feed probe was changed just
enough to avoid infringing on the original ADL patent. Performance
on Ku-band indeed suffered from the original.
While you may pay more for an ADL feedhorn, it is made in the U.S.,
and with the 3 wire servo motor connection you will be able to precisely
set the proper skew for each polarity. An A/B comparison of the RP-3
versus any of the C/Ku LNBF devices will show superior performance
with the ADL feedhorn. General comment has been that you lose 15 to
20 percent of the ku-band signal on the C/Ku LNBF, compared to a feedhorn
with separate LNBs.
The difference in performance and the ability to select individual LNBs
for specific stability requirements is one of the advantages of using a
C/Ku feedhorn. You will certainly pay several times more (when the
cost of LNBs is added in) than a C/Ku LNBF, but it is the only way to
extract true performance on both bands with a single device.
