[TowerTalk] Grounds, 'remote' towers, 'house' power system

Wed Jan 13 13:30:44 EST 2016

Lightning can be thought of as a constant current source. A strike will
contain X amount of amps and it will conduct that amount of current to
earth. If there is resistance/inductance in the path, the voltage will rise
to whatever is needed to maintain the X amount of current.

So yes, leaving ungrounded coax cables laying on the floor is a bad idea.
The voltage will rise until it is high enough to create an arc to a path to
earth to dissipate the charge.

You most always should have two ground systems unless your tower is right at
the shack entrance.
The tower should have its ground system at the tower base, ground rods
radials etc.
Then you need a similar ground system at the shack entrance where your
single point shack ground system gets grounded. This needs ground rods,
radials etc.

You should always tie both ground systems together and to the power ground
for safety. The ground lead between tower and shack will dissipate some of
the lightning energy and help equalize voltages in the area but it should
not be a substitute for a ground system at either end.

Both ground systems are important as you want to discharge as much energy to
earth right at the tower as possible if the tower is struck or energy is
induced into it.

The ground system at the shack will take up a lot of what is left over that
the tower ground system did not take care of and it will dissipate a large
part of energy if a strike comes in on the power line or phone/TV etc.
lines. 

Having all the equipment, power, coax etc tied together at the single point
ground panel keeps the potential the same on all lines as they enter the
shack. The fact that the single point panel has a ground lead a few feet
long to its ground system will allow some voltage rise there but all lines
to the equipment will have near equal voltage.

If the power comes into the shack from a ways away of the other side of the
house a good thing to do is run an ac line (from an outlet in the shack)
over to the single point ground panel where AC protectors are placed on that
line and then power all of your equipment only from that AC outlet on the
single point ground panel. That will place the AC power at the same level as
the coax lines.

73
Gary K4FMX

> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> StellarCAT
> Sent: Wednesday, January 13, 2016 11:16 AM
> To: tower
> Subject: Re: [TowerTalk] Grounds, 'remote' towers, 'house' power system
> 
> Hi Stan and thanks,
> 
> Gary here... I'm sure we're on the same page ... but...
> 
> I'd take exception with some of this. First it is actually the voltage
> that
> does most of the destruction - ok - lets say 'a good deal' of the
> destruction - albeit the current through an inductor is what causes that
> voltage to rise very rapidly and to whatever voltage is needed to
> complete
> the circuit and keep the current flowing ... leaving the coax on the
> floor -
> the path that it can find IF through that is established because the
> voltage
> goes extremely high breaking down the path and thus allowing the current
> to
> (continue) follow that path. That stated of course high currents that
> are
> conducted over any conductor will cause damage as well - so bottom line
> is
> it is both voltage and current...
> 
> I'm sure we've all seen the trick of leaving the coax on the floor and
> watching arcs from the center to the shield ring of the connector ...
> voltage.
> 
> And one would need to take care when saying "all equipment being at the
> same
> potential"! The real world has inductances all over the place - so there
> are
> differences in voltage all over the place. Getting to a close
> approximation
> is all one can hope for. Indeed if one has no damage strike after strike
> I'd
> agree they've gotten 'close enough' for all practical purposes. But just
> running wires in essence gets you to a DC ground ... not necessarily or
> even
> probably a lightning ground.
> 
> What I want to happen is for the energy to be dissipated at the tower.
> If I
> can keep the path from not being through the coax/control lines then an
> effectively placed ground system will do just that. Connecting any wire
> of
> reasonable size (affordable) over long distances just muddies the
> waters.
> 
> I just re-read an article on lightning protection in QST back in 2002
> ...
> and indeed it suggests if the distances are more than 100' to establish
> SPG
> at each end and to not connect them together. Likewise it suggests
> longer
> runs of cable/coax - being poor conductors due to their high inductance
> -
> reduce the currents - and thus voltages - to the far end ... i.e. the
> shack.
> 
> Gary
> K9RX
> 
> 
> -----Original Message-----
> From: Stan Labinsky Jr.
> Sent: Wednesday, January 13, 2016 11:50 AM
> To: StellarCAT
> Subject: Re: [TowerTalk] Grounds, 'remote' towers, 'house' power system
> 
> -----Original Message-----
> From: StellarCAT
> Sent: Wednesday, January 13, 2016 9:28 AM
> To: tower
> Subject: [TowerTalk] Grounds, 'remote' towers, 'house' power system
> 
> >I'm a bit confused by the push to connect my tower to the house power
> >coming in - direct of course ... but nonetheless connected.
> 
> Well Stellar, we tie the antenna system ground and the power ground
> together
> so that the bulk of the strike current does NOT flow through the
> equipment.
> 
> If you look at the typical setup, every time you hook up the coax and
> plug
> in the radio you have already made that connection (between the antenna
> ground and power ground) but, do you really want strike current to use
> your
> radio as a path to equalize the strike potential?
> 
> The direct connection attempts to bypass the "thru-the-rig" strike
> current
> flow.
> 
> Add to that, ALL the radio equipment's grounding connections (the green
> wire, the round pin on the power plug) should be tied to the antenna
> grounding point where the antenna leads enter the building, referred to
> as
> the Entrance Panel in some literature.  Check out PolyPhaser White
> Papers on
> the subject... eye opening!
> 
> That way ALL the radio equipment is at the SAME potential during the
> strike
> event (picture the radio being inside of a bubble, connected to the
> outside
> world at ONLY ONE POINT), so NO, or very little strike current flows
> through
> your equipment.
> 
> BTW, it is strike CURRENT that kills radios!  Current pulses flowing
> over
> the ground circuits inside that thousand dollar radio will kill
> sensitive
> components by the inductive coupling between circuit traces on the
> printed
> circuit boards.  Yea, really!
> I've even heard of a situation (actually mentioned during a paid
> electronics
> noise elimination course I was enrolled in years back) where strike
> current
> flowing down to ground by way of the building's lightning rod's down
> lead
> inductively coupled energy into the building's power wiring, lighting up
> the
> whole 110/220 being fed to the office computers with shocking results.
> It
> does happen.
> 
> Now, assuming that you lay those unhooked antenna cables on the ground
> outside of your shack, well, OK.  But there are reports of folks who
> just
> laid the unhooked cables on the shack floor.  Lightning came for a visit
> and
> found whatever path to ground it could to discharge itself.  The fire
> department then came and cleaned up the mess.
> 
> Hope this gives you some new ideas to consider.
> 
> 73 Stan
> 
> _______________________________________________
> 
> 
> 
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