On 11/26/2014 5:14 PM, Jim Lux wrote:
On 11/26/14, 2:00 PM, Martin A Flynn wrote:
The N2MO station has an external GPS antenna on the gable end of the
building. It's connected to the polyphaser arrestor with FSJ4-50
superflex.
The antenna mounting pipe has a #2 ground wire (33.6 mm/2) the
polyphaser has it's own #2 ground wire. Both connect to an 8' x 5/8"
(2.4m x 16mm) driven ground rod. The jacket of the superflex is
grounded with the factoryt Andrew kit as well
Even with the GPS antenna lower in elevation then the HF beam and other
antenna (with similar protection) I have concerns about leaving it
connected all the time.
AWG #2 seems a tad overkill, the current in a stroke can be carried by
AWG #10 without melting, but maybe you had a lot of it around for
other reasons. I suspect the coax shield has smaller cross sectional
area than AWG #2 and you'll protect your grounding wire by blowing up
the coax<grin>. (in fact, looking at the data sheet for FSJ4-50, the
DC resistance of the outer conductor is 1 ohm/1000 ft = AWG 10.. it's
actually more resistance than the inner conductor (the inner conductor
is 0.820ohms/kft, and 0.140 inch in diameter, compare to AWG 10 which
is very close to 0.100 inch in diameter).
Hopefully your driven ground rod is bonded to the other system grounds?
I'd worry about multipath from the HF beam and tower (although maybe
you're not using that GPS for time-nuts 1E-20 precision...<grin>)
The #2 copper was recycled. The main RF grounding trapeze is tied to
the grounding electrode system with 1/0, which was also recycled from
another project.
Re the time-nuttery: Only 1E-14. Can't afford better (yet).
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