[160m] ESD/Lighting Protection

[fkamp at comcast.net]

Tom Rauch wrote:
> 
> > Actually I intedt to put Polyphasers and ground the heck
> out of everything.
> 
> Grounding is 99% of the cure. There isn't a single
> polyphaser or other lightning protection device in any cable
> here, and I take several strikes a year without any problem
> except for occasional cables that blow apart before they
> reach the house. No protection device would prevent that, so
> I live with it.
> 
> > My concern is if I manage to get a fourty foot mast up it
> will be the
> > highest metal obeject in several tens of square miles.  We
> have had several
> > strikes in the neighborhood, I've just been lucky so far.
> The lightning rod
> > would act as a drain for my property and give a strike a
> path should one
> > actually hit.
> 
> Lightning rods don't do anything except act as a target. In
> your case, with a metal pole, the change would be very minor
> with or without a rod. The biggest improvement comes from
> *proper* grounding.
> 
> > Another concern is ESD, Electro Static Discharge.  I had a
> six foot pipe
> > with a 2m 5/8 wave whip on top.  I disconnected the co-ax
> from the radio
> > during a sand storm but there was enough of a charge
> generated that a bush
> > of corona three inches long shot out of the end of the
> cable into my
> > computer and packet modem.
> 
> You may need to rethink grounding. The voltage breakdown of
> RG58 and larger is normally limited by the connector air
> gap. With "N" or BNC connectors it's maybe 4000 volts peak.
> With UHF connectors it is about 5-6 thousand volts. The
> "spark gap" in a connector will normally arc first.
> 
> The only way to have  3" of corona is to have the the shield
> isolated from ground with very little leakage. That would
> indicate an improperly grounded (not to national code) cable
> entrance.  I'd correct that!
> 
> > What kind of problems are created with 500' of wire
> running right up the
> > rear of a radio or will a polyphaser handle a constant
> discharge for hours?
> 
> If the 500ft of wire is in a shoebox lying on the ground,
> almost none. If the 500ft of wire is all entirely vertical,
> it's a huge problem.
> 
> I'd never depend on a lightning suppression device as the
> main protection. The main protection comes from proper
> grounding. Commercially manufactured lightning protection
> devices are OK, but not on multiband antennas that require
> an antenna tuner.  Some are even marginal at handling a KW
> into matched loads.
> 
> My transmitting system comes in to a DX Engineering antenna
> switch box that has relays. When power is off, the
> transmitting antennas are disconnected. My control cables
> and receiving antennas are connected all the time, however.
> 
> I basically never disconnect anything, and have a fairly
> large system.
> http://www.w8ji.com/my_shack.htm
> 
> Grounding is the key.
> 

I have to agree with Tom.  Grounding is the key.  However, I'm not so
sure that a properly grounded lightning rod would be a bad thing.

I have been in one location, near Dallas, Texas, since 1978.  During
that time I have had a 55 foot tower, with 2-meter vertical at the top. 
The vertical brings the total height to 65 feet which places it as the
highest point on my property.  It is higher than the ground wires
running across the tops of the power poles, hence subject to lightning
strikes.

My tower is grounded.  The HF beam at the top of the tower is also at DC
ground.  The 2-meter vertical is also at DC ground as are the multitude
of wire antennas below the beam.

You can consider the 2-meter, grounded vertical as a tall lightning
rod.  At least that is what I consider it to be.  Lightning rods don't
attract lightning.  They allow the static buildup to dissipate before it
reaches the magnitude needed to generate a catastrophically concentrated
discharge.  At least that is my take on it.

I could be all wet, but I know what works for me.

We have plenty of electrical storms in the spring and in the fall every
year.  None of those events have ever caused any problems at this
location over the 26 years that the antenna system has been up.

No damage that could be attributed to lightning strikes, no blown
cables, no burned fittings or connections, and no damage to any
equipment.

Of course I do take time to disconnect the antenna feeds from equipment
during an electrical storm.  No need to tempt fate.

Regards,
Frank Kamp
K5DKZ