That is a catch 22.
The NEC for residence is not the same for a Radio Station, and R56 -
Standards and Guidelines for Communication Sites. However we have a
residence and a Radio Station on the same lot.
Proper ground system for both requirements are very expensive and ignored by
most of ham stations I visited on my previous antenna business.
It is not what to do with the neutral only on the 240Vac amplifier, it is
the RF ground, AC ground and neutral at the residence and at the station.
The Towers ground has another complication, lighting and RF ground plane.
Besides the NEC code and R46. The ground for lighting requires a 00 cable
from the leg of the tower to several ground rod. The ground for RF require
radials, The ground for NEC requires only one point of connection with the
AC entrance ground, where the NEUTRAL is connect, and ALL the NEUTRAL must
be connected to only that single point, next to the AC meter, or AC
entrance. There is one ground rod there for that.
Also any rotor cable, control cable and any coaxial cable from the tower
must be properly grounded in several points.
All this complexity goes to the station with cables coming from the tower
into the Amplifier and cables from the amplifier to the AC wire of the house
including the neutral !
The solution at my station to comply and be safe with all standards
requirements was to use a 240Vav 3KW medical isolation transformer for the
110AC at the station and the center to the RF ground outside the house. The
same 240Vac line from the Amplifier and the isolation transformer does not
use the neutral from the house wiring, but goes to the outside RF ground
that has a 00 cable and several ground rods with only one connection to the
Neutral at the AC entrance, the same as the AC outlet on the wall from the
house wiring. All my cables and from the tower are grounded outside the
house, inside a large steel galvanized box, grounded on that 00 cable.
So, the neutral is connected as NEC requires, it is safe and comply with
r56. The 240 Vac to the station has a larger AC common mode filter with the
house neutral at the input and only to phases out for the 240 Vac, for the
amplifier and the isolation transformer, the center of the secondary 110+100
is the neutral of the station, connected to the house neutral in only one
point at the entrance of the house. No neutral loop ground!!
If you don't follow all requirements, your station will suffer severer
damage with any lighting event and the way you connect the neutral to your
amplifier will means nothing. Be safe.
73's
JC
N4IS
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