The Cushcraft R-8 is the latest version of the 30-year Cushcraft R-series of
Muli-band vertical antennas (R-3, R-4, R-5, R-6000, R-7000, R-7000+, and R-8).
Except for the R-3, ALL of these antennas use a black matching box at the feed point.The usage and type of traps has varied over the past 30 years.
Cushcraft R-8 Manualhttp://www.qsl.net/4/4x6on/RADIO%20MANUALS/CUSHCRAFT/CUSHCRAFT--R8-User-manual.pdf
The Cushcraft R-8 takes considerable time to assemble (2 hours is not uncommon),
the proper assembly of the INSULATORS and aluminum CLAMPS for the
6, 10, 12, and 15 meter stubs is critical (avoid improper shorting, etc.)
Is this antenna BAD (high SWR) on ALL bands??The CORE R-8 radiator, below the first trap, is a 17/20 meter vertical.
This is different from earlier R-series designs, which were 10 meter radiators before the traps.
IF those are proper, then the MN8 matching box or BT1 / BT2 traps are only other parts to suspect.