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RE: antenna rig and Lightning




 
> > I have experienced a lightning strike on my antenna's and in my house, where
> > it completely damaged my radio gear, even finding its way to the fax machine
> > and video player.
> > 
> > I agree with Phil on disconnecting all from antenna's and outlets.
> > 
> > Get into the habit of disconnecting all antenna's and equipment from power
> > outlets( when not in use ), also your line to the telephone modem. Even when
> > there is no storms about as it's very easy to forget.
 
> 
> May I recommend another solution...  Like most of us with multiple radios and
> antennas, I don't (and most likely never will) disconnect all of my radio antennas
> during a storm.  If I did that liveing in Iowa, I'd wear the coax connectors out :-)!
> 
> Its been my experince that most damaging voltage spikes come in through the
> power line and telephone lines.  I suspect that the telephone is the worst offender.
> My entire station including the computers is connected to power through a 
> single bladed disconnect switch (fused).  This is simple old fashioned safety.
> Remember the old ARRL "Switch to Safety" ads?
> 
> When the storms come up, I pull the switch and shut down the main bench.
> If you want more "automatic" protection, run your modem phone line through a
> DPDT relay with the relay coil activated by the 120VAC power.  Shutting the power
> off automatically disconnects the modem line, simple!
> 
> You can also run your feedlines through PolyPhaser surge suppressors to protect
> the antenna connections.  These are used on every commercial installation I have
> seen in my area.  Heavy braided ground connections and good ground rods will
> complete the installation.  
> 
> Interestingly enought the local two meter repeater (with three antennas connected,
> UHF links, etc) stays on and connected through every storm.  It has never suffered
> any damage.  I keep expecting it, but it has not happened in 12 years.  It sits in my
> shack ten feet from my operating bench.  I must be lucky (or the 
> repeater is)!
> 

Although the following somewhat depends on what type 
antenna you are using,  I have come to the conclusion that 
although disconnecting your antenna may reduce the damage 
if you GET a strike, depending upon how your antenna is 
grounded, disconnecting it COULD make a stike more 
probable. 
     If your antenna is grounded via some means other than via 
the shield on the coax, then this wouldn't apply, but many of 
us just have an un-grounded antenna with a coax leading to 
the radio.  This is not a good situation, but is often the only 
simple way to do things.  When your  antenna is connected  
to your radio, and the radio is plugged in, it provides a ground 
path to discharge static charges that develop during a storm. 
Usually, you won't get a lightning strike unless these static 
charges build up, so if you have a path to ground, you will 
neutralize the static charge and reduce the voltage difference 
between the cloud and ground, thus making a strike less 
likely.   If you unplug the radio or disconnect the antenna at 
the radio, then you are allowing the static charge to build up 
on the radio and are making a strike more likely AND you are 
providing a nice path for the strike to come into your shack.
   I used to disconnect antennas all the time, but after several 
cases of seeing sparks jump a foot from where I laid the coax 
down over to the case of the radio, it finally sunk in what I was 
doing.  Since then, I have tried to either keep at least the 
ground connection of the coax connected to the radio, and 
perhaps disconnect the center wire via a multi position switch.
Since I've done this, I've never had a problem.


+----------------------------------+
| Bill Jones, N3JLQ,Sweden, Maine  |
| wejones@megalink.net             |
| http://www.megalink.net/~wejones |
+----------------------------------+
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