Gentlemen,
I have a 31 meter tall bottom fed vertical in Florida that
is located right on the edge of the water. It gets hit two
or three times a year (not always directly). I used to
suffer serious damage until I installed the following
lightning protection:
1. Whenever I switch the power off to the transceiver, a
"linear actuator" automatically grounds the bottom of the
vertical via a 5 cm (2") wide ground strap (to a
substantial ground). The linear actuator is a surplus from
a boat, where it was used as a trim-tab actuator. It has
about a 10 cm (4") throw, so it does not cause any stray
capacitance when in the retracted position. An alternative
could be an old Satellite TV dish actuator. You can often
see them cheap at hamfests.
2. At the same time a 20 kV normally open vacuum relay
dsiconnects the coax center conductor.
3. At the shack end the coax is rolled into a .7 meter
(2') diamter, 6 turn coil. At the entry point, the braid
of the coax is grounded to large ground bar and a ground
system of four 2 meter ground rods. Another vacuum relay
disconnects the center conductor of the coax going into
the shack and grounds it (i.e. the PA output gets
grounded).
4. On the 240 VAC power side, I have installed three
60,000 A varistor type surge absorbers connected in a
delta configuration (i.e. one arrester each from L1 and L2
to ground, and one between L1 and L2.) I have also
installed the same on the main AC panel, where the AC
service enters the house. That surge arrester group uses
the utility ground.
While all the above sounds excessive and a big job, it
took that much to be able to survive hits without damage
or the need to disconnect equipment all the time. Earlier,
I have tried gas discharge surge arresters, etc., but
nothing really worked 100%. Since I have installed the
above system I had no problems. (But I had to replace the
grounding strap once, as it partially melted during a big
strike.)
GL,
George, AA7JV
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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