wrote
Here's what I'm doing and I'd like some feedback.

Antenna will be an 88ft doublet 30-40ft high supported at the center by
a ladderlock and fed by 450ohm windowline. The windowline will drop
down to within 8ft of the ground (above kiddie reach) where it will be
connected to a W2DU style choke balun based on RG213 and Palomar BA-8
ferrites. This will be enclosed in a ~12" length of electical conduit
which will be supported to relieve the windowline of further strain.

The coax will connect at the bottom of the choke enclosure via
PL259/SO239 to a ~10ft length of RG213 down to earth level driploop and
up into a small lockable mushroom enclosure containing a ICE300
supported on a 5/8"x8ft copper ground rod. Also contained in the
enclosure will be an LDG RT-11 tuner which will be mounted on the
backside of the ground rod from the ICE300. A small RG213 jumper will
connect the ICE and RT. The shell of the shielded DB-9 control line
will have a small braid to bond it to the ground mounting point as
well.

The coax and shielded DB-9 control lines from the RT will drop out of
the enclosure via PVC conduit to an undergound PVC junction box which
has it's bottom side perforated to drain any condensate. The run to the
house from this JB is ~50ft with a 1ft rise which should ensure a flow
of any condensate to the JB drain. The RG213 will be direct burial
grade but I've not been able to find any shielded DB-9 direct burial
cable hence the electrical PVC conduit.

At the house end the PVC will sweep up to another small enclosure atop
another 5/8"x8ft ground rod holding a grounding point for the shells of
the coax and control lines and also will terminate the line from the
station bond from inside the shack. The lines will then enter the house
through a driploop and travel ~5ft to the shack.

At the shack a ground bus will be provided where each of the pieces of
equipment will be bonded individually. This ground bus will be
connected via a 3" copper strap 5ft back out to the ground rod at the
entrance to the house.

The station ground outside the house is 40ft away from the service
entrance and its ground. I'm thinking of running "something" from the
station ground rod to the service entrance. I can easily periodically
"terminate" this with some intermediate ground rods if necessary along
its length.

What should the "something" running between the station and service
ground rods be?

How often should any periodic termination rods be added?

Any help on direct burial shielded DB-9 cable?

tnx
jtm


Jim, if you use twin-lead from choke-to-tuner as Cecil suggested, the coax
arrestor model at the tuner can be changed to ICE-304U per
http://www.arraysolutions.com/Produc...mpulse1.html#2

40' is at least 2x too long for a bonding jumper, according to a PE's
interpretation of NEC-70/NFPA-780. That leaves up to you what to do to
mitigate this problem. Practically speaking, you can not provide a low
impedance connection that far no matter what conductor was used. But
compared to the home's AC ground wiring which is outrageously high
impedance, you can provide reasonable equipotential with the service ground.
A minimum of one 8' copper clad ground rod, driven 10' into the ground every
2x rod depth feet is the code requirement for grounding electrodes. Applying
that electrode-length requirement to a distance too long for a bonding
jumper is not defined in the code, hence the professional opinion that was
required in my case, which I share with you. In that similar situation, I
used 4' copper ground rods every 8' along the bonding-path to the service
entrance. The risk involved with such a long jumper is Ground Potential
Rise. This could draw current from the station ground up into the bonded
equipment cases, overpowering the withstand design of the equipment, and
exiting the equipment via the AC connections and coax feedlines. As long as
you provide a bond that is significantly lower impedance than the AC wiring
to the service ground, you have minimized GPR-risk. Not eliminated it. The
better the bonding and voltage-division your ground system provides
(radials, improved service entrance ground, ground rings, ufer-grounds, etc)
the more protection from GPR you provide. Your bonding must be capable of
balancing the GPR across the entire system. Since the withstand of most
equipment is approximately 2,000v, you should not have a problem maintaining
a much lower potential than that.

The only other thing I would add, is an ICE-300 on the equipment ground
bus-bar, after first shield-grounding the coax feedline at the station
single point ground.

73,
Jack Painter
Virginia Beach, Virginia