On 26 Jan 2005 05:45:12 -0800, wrote:

I think I just had an ephihony,

A regular j pole uses a shorted stub, so, If the regular j pole was
grounded, no need to cround the coax?

Ah not quite. The coax shold be grounded also. See the PolyPhaser
site about lightining protection. It makes little difference as to
the type of antenna from a practical standpoint of lightining
protection.

The key issue around lightining is what are best described as sneak
paths. Due to the imense current (in excess of 10,000 Amps) even a
fraction of an ohm resistance difference between the strike point and
ground allows a significant voltage to develope (10,000A*
0.1ohm=1000V). I might add that in that example a resistance of 0.1
ohm is likely an unrealisticly low number. Also since it's a pulse
of energy it induces currents just like the magnetic field in a
transformer or generator so even nearby conductive objects can have
currents and voltages induced on them. This gives rise to those sneak
paths. So this means if you want tp prevent a lightining hit (or
near miss!) from finding its way into the shack you will have to pay
attention to details. This includes phone and power lines. I've
not gone into a lot of explanation here and I've glossed over much
as well so please research it deeper.

As side note: I've been hear missed three times and all three times
the greatest destruction came via the phone lines! I've lost phones,
computers because the spike was propagated from the phone to the
computer that was connected to it via an external modem. This can
give an idea of sneak paths. To truly effect a Lightining protection
plan you have to address the antenna system (antenna, tower,
feedlines), the power system (what the radio runs off of) and the
phone system (you may have a computer with DSL, cable modem
or Phone modem connected to the radio). It's not difficult but,
attention to small details and following known guidelines is
important. Oh and don't scrimp, a good system is cheap compared
to damaged electronis or a house fire.

Allison
KB1GMX