Operation during storms
Jeff
Hello all,
I would like to be able to operate my rig during an electrical storm
without worrying about lightning strikes if that is possible. Right now
I have a copper ground rod outside driven in the ground and the wire
wrapped around the PL-259 on the radio and also on the radio itself (on
one of the screws). Also, I have the radio itself plugged into an APC
surge supressor, which I know will protect it from surges originating in
the power line, (one of them has saved my computer twice now, heh) I am
just concerned with strikes to the antenna itself.
Jeff
Please reply via email, I don't get to check the newsgroups much
anymore.
Bob Lewis
The only way to protect yourself is don't be anywhere near the radio or
antenna connections during a lightning storm! You can do lots of things to
minimize damage from surges caused by nearby strikes but if you get a direct
hit on your antenna and you are hanging on to the mike, your odds are not
good.
Bob Lukaszewski
Jeff wrote:
>
> Hello all,
> I would like to be able to operate my rig during an electrical storm
> without worrying about lightning strikes if that is possible. Right now
> I have a copper ground rod outside driven in the ground and the wire
> wrapped around the PL-259 on the radio and also on the radio itself (on
> one of the screws). Also, I have the radio itself plugged into an APC
> surge supressor, which I know will protect it from surges originating in
> the power line, (one of them has saved my computer twice now, heh) I am
> just concerned with strikes to the antenna itself.
>
> Jeff
>
> Please reply via email, I don't get to check the newsgroups much
> anymore.
What in your miserable life could be worth the chance of getting fried
to operate during an electric storm..???? This is a hobby pal..and its
the last thing I would be doing during an electric storm unless Im on
my HT in a local Skywarn net... Its just not worth it..!!!!
Enjoy the hobby... the storm will go away fairly quick...
73
--
******************************************************************************
Bob Lukaszewski K4HA Reply to 'rlu...@nortel.ca' or
'k4...@mindspring.com'
The views expressed are all mine... Yaddi Yaddi Yaddi !!!!!
Gary Coffman
On Fri, 17 Apr 1998 07:44:51 -0400, Bob Lewis <aa...@erols.com> wrote:
>The only way to protect yourself is don't be anywhere near the radio or
>antenna connections during a lightning storm! You can do lots of things to
>minimize damage from surges caused by nearby strikes but if you get a direct
>hit on your antenna and you are hanging on to the mike, your odds are not
>good.
Those of us charged to maintain 24x7 commercial operations would be
surprised to hear that. It is possible to handle direct strikes to the antenna
without harm to personnel or equipment failure. (If it weren't, we'd be off
the air every time a thunderstorm came by.) It is not simple to do so,
however. Very careful attention to detail is required. This is where the
professionals earn their exorbitant consulting fees. :-)
I've written extensively about this subject on this group a number of times.
Consult Dejanews for the details. And order Polyphaser's book, "The
Grounds for Lightning and EMP Protection". It doesn't cover everything,
but it is the best generally readable reference for dealing with lightning
surge in radio installations.
Gary
Gary Coffman KE4ZV | You make it |mail to ke...@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
Bob Lewis
Of course you are right. I was limiting my thinking to what the typical (whatever
that is) ham might do for a home installation. I doubt that the little arc-plug
devices connected with a peice of 16 guage wire will provide much protection :)
Rich
On Fri, 17 Apr 1998 03:30:03 -0400, Jeff <tre...@highland.net> wrote:
>Hello all,
> I would like to be able to operate my rig during an electrical storm
>without worrying about lightning strikes if that is possible. Right now
>I have a copper ground rod outside driven in the ground and the wire
>wrapped around the PL-259 on the radio and also on the radio itself (on
>one of the screws). Also, I have the radio itself plugged into an APC
>surge supressor, which I know will protect it from surges originating in
>the power line, (one of them has saved my computer twice now, heh) I am
>just concerned with strikes to the antenna itself.
>
Your current setup is just *barely* adaquate to protect against static
discharge. If you're really interested in operating during storms
( or, for that matter, if you're interested in just protecting your
equipment at all ) you need to use an approprately grounded entrance
panel, feedlines, etc. As for the surge supressor - if it is anything
like the other APC supressors that I have seen, it does NOT protect against
all transients, especially those in the lightning-strike class.
I'd suggest getting some literature from companies like Polyphasor, etc,
who specialize in lightning protection. It won't be cheap, but if you
really want to operate during a storm, it is possible.
- Rich
--
Rich Mulvey
My return address is my last name,
followed by my first initial, @mulveyr.roc.servtech.com
http://mulveyr.roc.servtech.com
Amateur Radio: aa2ys@wb2wxq.#wny.ny.usa
Jeff
What would the risk level be in operating from a battery with an indoor
antenna? This would eliminate the problem with AC strikes, but would an indoor
antenna be prone to being struck?
Jeff
btw: thanks for all the helpful posts
Bob Lewis
Jeff wrote:
> What would the risk level be in operating from a battery with an indoor
> antenna? This would eliminate the problem with AC strikes, but would an indoor
> antenna be prone to being struck?
Probably no more than the chances of any other metal object inside the house.
Depending on the freq and power you probably want to consider the RF Safety issues
though.
How about those who talk on a wired telephone during a storm, hanging on to the
end of several miles of wire hung up in the air. That's putting a lot of faith in
the phone companies lightning arrestors!
Gary Coffman
On Fri, 17 Apr 1998 12:38:51 -0400, Bob Lewis <aa...@erols.com> wrote:
>Of course you are right. I was limiting my thinking to what the typical (whatever
>that is) ham might do for a home installation. I doubt that the little arc-plug
>devices connected with a peice of 16 guage wire will provide much protection :)
Very true. You need a complete site plan that includes designed primary strike
paths, an excellent Earth terminal, and use of ground windowing technique to
avoid differential potentials across the protected area. Suppressors are part
of the site plan, and they have to be the proper suppressors, properly installed,
but they are only a part of the plan.
The key to good lightning protection is to understand that every detail counts.
You can't overlook *anything* in your site plan. If you do, you'll undo every bit
of protection you have installed. In other words, you can't go at this half-assed,
it is whole hog or nothing. It is quite possible that a *partial* lightning mitigation
installation can lead to greater levels of damage than no mitigation measures
at all.
Everybody read that last paragraph again. This is vitally important to understand.
There is no such thing as incremental protection against a strike. Half-assed
protection can lead to greater harm than no protection at all. Do it right, or
throw your coaxes out into the yard every time there's a cloud in the sky. (And
even that won't help if the antennas are mounted to the house.)
Gary Coffman
On Sat, 18 Apr 1998 09:46:13 -0400, Bob Lewis <aa...@erols.com> wrote:
>Jeff wrote:
>
>> What would the risk level be in operating from a battery with an indoor
>> antenna? This would eliminate the problem with AC strikes, but would an indoor
>> antenna be prone to being struck?
>
>Probably no more than the chances of any other metal object inside the house.
>Depending on the freq and power you probably want to consider the RF Safety issues
>though.
Yep.
>How about those who talk on a wired telephone during a storm, hanging on to the
>end of several miles of wire hung up in the air. That's putting a lot of faith in
>the phone companies lightning arrestors!
You bet, more than is deserved in many cases. I've seen phone instruments
totally blown apart by a strike. I'd hate to have been holding it at the time. But
that's generally due to a lack of maintenance of the phone system protective
measures. They really are quite good for preventing harm to personnel. They
aren't good enough to prevent harm to solid state electronics in many cases,
however, and you need to take your own steps to deal with that.
And woe be unto you if you interface the phone circuit with other systems
with separate grounds. That's an invitation to disaster. You have to ground
window everything to prevent problems caused by potential differentials
derived from the strong earth currents involved during a strike.
Rich
On Fri, 17 Apr 1998 23:06:22 -0400, Jeff <tre...@highland.net> wrote:
>What would the risk level be in operating from a battery with an indoor
>antenna? This would eliminate the problem with AC strikes, but would an indoor
>antenna be prone to being struck?
>
It certainly wouldn't be prone to being struck, but it would still
be prone to having substantial damage from spikes induced by a nearby strike.
You still need to take proper precautions.
Ron Schwartz
Gary Coffman wrote:
>
> >How about those who talk on a wired telephone during a storm, hanging on to the
> >end of several miles of wire hung up in the air. That's putting a lot of faith in
> >the phone companies lightning arrestors!
>
> You bet, more than is deserved in many cases. I've seen phone instruments
> totally blown apart by a strike. I'd hate to have been holding it at the time. But
> that's generally due to a lack of maintenance of the phone system protective
> measures. They really are quite good for preventing harm to personnel. They
> aren't good enough to prevent harm to solid state electronics in many cases,
> however, and you need to take your own steps to deal with that.
>
> And woe be unto you if you interface the phone circuit with other systems
> with separate grounds. That's an invitation to disaster. You have to ground
> window everything to prevent problems caused by potential differentials
> derived from the strong earth currents involved during a strike.
One example I had to deal with 1st hand was about 15 years ago. The
company I worked for ran a 50m long conduit between 2 buildings with a
900-pair cable inside for both voice and data. The conduit took a
direct strike on a short section between where it exited one building
and went underground.
We had flames coming out of the data switches and modem banks in machine
rooms in _both_ buildings. All the PBXs for phone service and outside
trunks were also fried. I spoke to some people who were on the phone at
the time and some had ringing in their ears for some minutes afterwards
because of the surge thru their handsets. No one was hurt except for a
poor guy working under a trailer right next to the conduit -- he wet
himself.
Knowing the team responsible for wiring up the complex, I doubt there
was any significant attention paid to lightning protection. At least
the modems acted as fuses and protected the computers.
VE3VN
Lab Assistant1
When designing a ground window and single point ground, does it
help to pass the coax, telephone, power, etc. wires through a second
panel with ferrous content or torroids AFTER the surge units on
the ground window? The purpose of this would be to help strip off
the magnetic energy or provide some type of low freq. RF choke.
Would it be helpful to put on a couple of torroids on all
interconnecting
cables with the idea of providing some minimum level of common mode low
freq. filtering?
I was able to find some heavy guage copper flashing 20in wide (for
$6.25/ft. it took me forever to find it) and plan to use it to make a
ground window/bulkhead for
all the antenna coax, etc. I want to place this panel on
the outside of my house and then feed the wires through the wall.
my ground bus inside the shack is a 3/4 in copper pipe running along
the back of the table. Is it a problem when creating a single point
ground that the radios, computer, power protector(like isobar), tel.
etc. are connected at different points
along the pipe and then that the pipe is connected to the ground
panel outside (with at least one bend along the way)? Does that violate
the SINGLE point system since the connections are inherently placed in a
row?
I dug up the old articles in QST regarding EMP from the 80's and it
seemed to me
that the radios they tested were surprisingly resiliant to EMP given
moderate protection. Is that still the prevailing wisdom or is there
new information regarding such events?
please reply to:
gte...@prism1.gatech1.edu1 (remove nospam one's to reply)
73,
KS4TY, Eddie
Rich wrote:
>
> On Fri, 17 Apr 1998 03:30:03 -0400, Jeff <tre...@highland.net> wrote:
> >Hello all,
> > I would like to be able to operate my rig during an electrical storm
> >without worrying about lightning strikes if that is possible. Right now
> >I have a copper ground rod outside driven in the ground and the wire
> >wrapped around the PL-259 on the radio and also on the radio itself (on
> >one of the screws). Also, I have the radio itself plugged into an APC
> >surge supressor, which I know will protect it from surges originating in
> >the power line, (one of them has saved my computer twice now, heh) I am
> >just concerned with strikes to the antenna itself.
> >
>
> Your current setup is just *barely* adaquate to protect against static
> discharge. If you're really interested in operating during storms
> ( or, for that matter, if you're interested in just protecting your
> equipment at all ) you need to use an approprately grounded entrance
> panel, feedlines, etc. As for the surge supressor - if it is anything
> like the other APC supressors that I have seen, it does NOT protect against
> all transients, especially those in the lightning-strike class.
>
> I'd suggest getting some literature from companies like Polyphasor, etc,
> who specialize in lightning protection. It won't be cheap, but if you
> really want to operate during a storm, it is possible.
>
Gary Coffman
On 19 Apr 1998 15:55:22 GMT, ri...@ucesucks.mulveyr.roc.servtech.com (Rich) wrote:
>On Fri, 17 Apr 1998 23:06:22 -0400, Jeff <tre...@highland.net> wrote:
>>What would the risk level be in operating from a battery with an indoor
>>antenna? This would eliminate the problem with AC strikes, but would an indoor
>>antenna be prone to being struck?
>>Jeff
>>
>
> It certainly wouldn't be prone to being struck, but it would still
>be prone to having substantial damage from spikes induced by a nearby strike.
>You still need to take proper precautions.
>
>- Rich
This shouldn't be a problem. QST published an article on a series
of tests done on amateur equipment in the Navy's EMP simulator.
Battery powered VHF equipment suffered no damage when used
with a rubber duck. A big indoor antenna might pick up enough induced
surge to present a problem, but an indoor quarterwave GP should be
Ok.
HF equipment, even with indoor antennas, is another story. There
can easily be enough inductive coupling to cause front end damage.
Gary Coffman
On Mon, 20 Apr 1998 12:51:38 -0400, Lab Assistant1 <laba...@prism1.gatech1.edu1> wrote:
>When designing a ground window and single point ground, does it
>help to pass the coax, telephone, power, etc. wires through a second
>panel with ferrous content or torroids AFTER the surge units on
>the ground window? The purpose of this would be to help strip off
>the magnetic energy or provide some type of low freq. RF choke.
I don't think this is a good idea. The purpose of a ground window
is to equalize potentials on all cabling entering or leaving the protected
area. Unless you can be sure that you don't get parasitic coupling between
the ground window plate and the ferrous plate, and unless you can be
sure the impedances are matched so that potential balance is maintained,
I think you might be creating more problems than you solve by doing this.
>Would it be helpful to put on a couple of torroids on all
>interconnecting
>cables with the idea of providing some minimum level of common mode low
>freq. filtering?
That's probably not helpful.
>I was able to find some heavy guage copper flashing 20in wide (for
>$6.25/ft. it took me forever to find it) and plan to use it to make a
>ground window/bulkhead for
>all the antenna coax, etc. I want to place this panel on
>the outside of my house and then feed the wires through the wall.
>my ground bus inside the shack is a 3/4 in copper pipe running along
>the back of the table. Is it a problem when creating a single point
>ground that the radios, computer, power protector(like isobar), tel.
>etc. are connected at different points
>along the pipe and then that the pipe is connected to the ground
>panel outside (with at least one bend along the way)? Does that violate
>the SINGLE point system since the connections are inherently placed in a
>row?
Yes it does. Using ground buss technique is a bad idea for strike
protection. Tie all cabling entering or leaving the protectied area
*directly* to the ground window in as symmetric an arrangement
as you can. This includes power and telco.
>I dug up the old articles in QST regarding EMP from the 80's and it
>seemed to me
>that the radios they tested were surprisingly resiliant to EMP given
>moderate protection. Is that still the prevailing wisdom or is there
>new information regarding such events?
And the simulator they used was producing NEMP (Nuclear Electromagnetic
Pulse) waveforms. That's much tougher than dealing with lightning EMP
because the risetime of the pulse is much faster. But realize they were
testing induced surge, not a direct strike. The latter is a horse of a different
color.
VHF/UHF equipment is fairly robust against EMP. (That's due to the low
impedance filter structures in the front end of typical VHF/UHF equipment,
and the small effective aperture of typical VHF/UHF antennas.)
HF equipment isn't as robust against this, with tube equipment generally being
more susceptable to damage than solid state equipment. (This may seem
surprising, but it is because of the generally higher input impedances in the front
end of tube equipment. Input coils often arc over, grid leak resistors fry, etc.
Solid state normally has a bandpass filter structure in the front end which
effectively limits the amount of surge energy entering the receiver, and for
transceivers, the PIN diode switches will generally clip the remaining pulse
to a level tolerable by active components.)
Now I don't mean to imply that you should neglect to use proper surge
suppression and station layout because of these factors. The design
factors of solid state help, but they don't offer anywhere near perfect
protection. You still need to do the other things to control surge (and
to survive direct strikes).
Dick Flanagan
In article <353f4dd5....@news.atl.bellsouth.net>, ke...@bellsouth.net
(Gary Coffman) wrote:
>On Mon, 20 Apr 1998 12:51:38 -0400, Lab Assistant1
<laba...@prism1.gatech1.edu1> wrote:
>
>>I was able to find some heavy guage copper flashing 20in wide (for
>>$6.25/ft. it took me forever to find it) and plan to use it to make a
>>ground window/bulkhead for
>>all the antenna coax, etc. I want to place this panel on
>>the outside of my house and then feed the wires through the wall.
>>my ground bus inside the shack is a 3/4 in copper pipe running along
>>the back of the table. Is it a problem when creating a single point
>>ground that the radios, computer, power protector(like isobar), tel.
>>etc. are connected at different points
>>along the pipe and then that the pipe is connected to the ground
>>panel outside (with at least one bend along the way)? Does that violate
>>the SINGLE point system since the connections are inherently placed in a
>>row?
>
>Yes it does. Using ground buss technique is a bad idea for strike
>protection. Tie all cabling entering or leaving the protectied area
>*directly* to the ground window in as symmetric an arrangement
>as you can. This includes power and telco.
I have no problem tieing all cables entering and leaving the shack to the
single window. The problem I have -- and where using a ground buss is very
attractive -- is for the myriad of grounds from all of the equipment in the
shack. It is very easy to have 20, 30 or more individual pieces of primary
and accessory equipment that need to be grounded. To provide each with an
individual ground run would create a wiring nightmare and in many cases
inductive ground run lengths of 20, 30 or more feet.
At what point can a low-inductance ground buss to a central point become
effective? In theory, if you made your central ground window large enough
to cover an entire wall, you could attach grounds to any point on that
wall. As you reduce the height of the wall, you approach a buss
configuration. When/why does this stop being effective? At what point
does the buss stop being an extension of the window and start becoming a
conductor to it? Why is a 20 foot length of 6 gauge wire direct to a
ground window better than a 4 foot length connected to a 16 foot length of
1" copper pipe running to the ground window?
Is the problem because the inductance between the different attachment
points on the buss will create voltage differentials between the attached
equipment? If that is the case, wouldn't the same effect result from
different lengths of direct ground runs?
I'm just trying to find a practical approach (not necessarily an easy one)
to solving a complicated problem.
73, Dick
--
Dick Flanagan W6OLD CFII Minden, Nevada DM09db (South of Reno)
Visit http://www.qsl.net/cvrc/
N1IIC
Have you ever seen the lightning rods on the top of the older type (mostly victorians and barns) buildings? Well, those don't attract lightning, they dissipate the charge before it can build up. See, lightning doesn't start in the clouds, it meets a 'feeder' from the ground. if there is no feeder, there is no strike.
That is explained by the quote from his article;
"While reexamining one of my old physics books, I came across a formula for the discharge from a sphere. My attention was attracted to the following sentences. "It has been previously shown that the maximum charge that can be retained by a conductor in air is limited by the fact that the air itself becomes conducting at an electric intensity of about 3 x 10>6 volts per meter. Vm=a*Em. Em is the maximum voltage; and, a is the radius of the sphere. For a sphere one centimeter in radius, Em=30,000 volts, and no amount of "charging" can raise the potential of a sphere this size, in air, higher than 30,000 volts."
And we all know that lightning carries a much greater voltage than 30,000.
Thus, if you were to install an inverted spear that
is well grounded above your installation, there will be no strike
in about a 50ft radius.
I will have the entire article and other lightning information posted
on my page as soon as I get time to finish it.
Hello Florida!! Gone for a week and 1/2!! Staying
with my elmer KA1UGH near Tampa. If anyone is in the central Florida area,
please email and we can try to sked a QSO down there!!
73 de Jason n1iic
Jeff wrote:
Hello all,
I would like to be able to operate my rig during an electrical storm
without worrying about lightning strikes if that is possible. Right now
I have a copper ground rod outside driven in the ground and the wire
wrapped around the PL-259 on the radio and also on the radio itself (on
one of the screws). Also, I have the radio itself plugged into an APC
surge supressor, which I know will protect it from surges originating in
the power line, (one of them has saved my computer twice now, heh) I am
just concerned with strikes to the antenna itself.
Jeff
Please reply via email, I don't get to check the newsgroups much
anymore.
--
AX.25 N1...@WA1WOK.NH
E-MAIL N1...@QSL.NET
Merrimack County
Mail:P.O. Box 13
Concord,N.H. 03302
Butch Magee
Well,..actually we have ground to cloud, cloud to ground, cloud to cloud
lightning, and 'ya don't have to get a direct hit...just a near miss can
kill everything attached to that antenna!
Butch said that!
gus
>When designing a ground window and single point ground, does it
I am rather new to this. What is a ground window. I know that the
books say to use a copper pipe that is grounded to attach your
equipment to. Is this the ground window? Also another guy posts that
doing the pipe thing is not good. He says to use one ground point???
what gives.
thanks
Gary Coffman
On Fri, 24 Apr 1998 13:21:11 GMT, lm...@swbell.net (gus) wrote:
>I am rather new to this. What is a ground window. I know that the
>books say to use a copper pipe that is grounded to attach your
>equipment to. Is this the ground window? Also another guy posts that
>doing the pipe thing is not good. He says to use one ground point???
>what gives.
A ground window is a metal plate (which may be an entrance bulkhead,
or may just be a plate mounted near the ham station) to which *every*
cable entering and leaving the station area is bonded. This includes
all antenna feedlines, rotator control cables, *AC power*, Telco, etc.
Wires that are nominally "ground" are bonded directly to the plate.
Wires that are nominally "hot" are bonded to the plate through a proper
suppressor. The bonds should be arranged symmetrically on the plate
so that no current from any bond must flow across another bond in order
to reach the central ground strap to the external ground field single point.
The purpose of a ground window is to equalize the potential between
all cables entering or leaving the station area. No potential difference
equals no damaging current flow through your equipment.
(The suppressors snub "hot" potentials to levels tolerable by the equipment
connected to them.)
The ground window is also bonded to your external Earth terminal. That
terminal should be your ground field *single point*. In other words, all
external grounds should tie to it in star fashion. (The National Electrical
Code requires all ground terminals to be bonded together.)
What you want to avoid is daisy chain or buss connections. Everything
should be star connected. External to the station, everything star
connects to your ground field single point. Internal to the station,
everything star connects to the ground window. These two are tied
together with a heavy low inductance strap.
It is absolutely essential that no wiring bypass this system. If even one
wire bypasses the system, all of the protection it offers you is lost. The
use of a ground window and a single point are central to good lightning
protection. There are other steps you have to take too in order to be
able to operate during a storm, but these two steps are essential.
Use of ground windowing and a single point is also helpful as a station
RF ground, though *stations typically don't need RF grounds*. What
sometimes does need an RF ground is certain types of antennas which
need ground to act as a counterpoise for their operation. But they need
that ground *at the antenna feedpoint*, not back at the station. That's a
separate topic.
Lab Assistant1
> A ground window is a metal plate (which may be an entrance bulkhead,
> or may just be a plate mounted near the ham station) to which *every*
> cable entering and leaving the station area is bonded. This includes
> all antenna feedlines, rotator control cables, *AC power*, Telco, etc.
> Wires that are nominally "ground" are bonded directly to the plate.
> Wires that are nominally "hot" are bonded to the plate through a proper
> suppressor. The bonds should be arranged symmetrically on the plate
> so that no current from any bond must flow across another bond in order
> to reach the central ground strap to the external ground field single point.
>
> The purpose of a ground window is to equalize the potential between
> all cables entering or leaving the station area. No potential difference
> equals no damaging current flow through your equipment.
>
> (The suppressors snub "hot" potentials to levels tolerable by the equipment
> connected to them.)
>
> The ground window is also bonded to your external Earth terminal. That
> terminal should be your ground field *single point*. In other words, all
> external grounds should tie to it in star fashion. (The National Electrical
> Code requires all ground terminals to be bonded together.)
>
> What you want to avoid is daisy chain or buss connections. Everything
> should be star connected. External to the station, everything star
> connects to your ground field single point. Internal to the station,
> everything star connects to the ground window. These two are tied
> together with a heavy low inductance strap.
Gary (or anyone else for that matter),
could you explain the physics why the use of a ground buss is bad?
My goal is a system that can withstand a lightning strike and reasonably
hardened to EMP, (all within reasonable expense :) and to learn the
engineering and physics principles behind it (no black magic). I have
read GLEP, but it was several years ago.
I don't understand how a length of copper buss which runs behind the
equipment to which the equipment is attached by short braid is worse
than running seperate (long length (which could be very long in a room
full of equipment) of) braid to the central ground connection.
computer TNC HF UHF phone patch rotor etc.
monitor | |
printer | |
| | | | | | |
----------------------------------------------------------- ground buss
| (low inductance)
short strap to
ground window
how is that ^ worse than running a (higher inductance) strap to
each piece of equipment?
along these lines...
when trying to design my station, there are some abvious physical
problems with running seperate ground straps and connecting to the
ground window. The biggest is that the ground window is on the exterior
wall of my house. and it will be difficult (and ham radio will go down
another notch or two with my wife) to punch another hole in the wall big
enough to connect all the ground straps and allow access to change
things around, plus problems with insulation, physical integrity, etc.
Would it also be acceptable to run a short strap (basically from one
side of the wall to the other) from the ground window to which all
the antenna surge protectors are bounded (external to the house) to
another panel inside the house to which all the case grounds, telco,
power, etc. is connected? This arrangement would make things a lot
simpler (for me), (but effective is what I need. :)
Thanks!
KS4TY, Eddie
reply to: le...@isye1.gatech1.edu1 (remove nospam one's to reply)
>
> It is absolutely essential that no wiring bypass this system. If even one
> wire bypasses the system, all of the protection it offers you is lost. The
> use of a ground window and a single point are central to good lightning
> protection. There are other steps you have to take too in order to be
> able to operate during a storm, but these two steps are essential.
>
Paul Silva
Gary Coffman wrote:
>
> What you want to avoid is daisy chain or buss connections. Everything
> should be star connected. External to the station, everything star
> connects to your ground field single point. Internal to the station,
> everything star connects to the ground window. These two are tied
> together with a heavy low inductance strap.
>
> wire bypasses the system, all of the protection it offers you is lost. The
> use of a ground window and a single point are central to good lightning
> protection. There are other steps you have to take too in order to be
> able to operate during a storm, but these two steps are essential.
read about lightning protection both in the newsgroups and elsewhere.
As I get ready to construct my station and ground system, I'm wondering
what one should do about the AC wiring that is already in place in the
room they are going to use as their shack. I'm sure that 99.9% of us
will
have our shacks in a room in our residence. That room will already be
wired for 120 VAC and it won't be going through any "single ground
point."
My plan is to bring 120 VAC and 240 VAC lines directly from the entrance
panel to my single ground point and then on to my shack (through proper
protection devices, of course). It seems to me that the wiring in the
walls of the shack is now a liability.
Having protection at the entrance panel is nice for power line hits,
but the induced variety can still find a path to the shack if the wall
wiring is still in, can't it? Should we be removing all the wiring that
is near our equipment but not routed through the single ground point?
Seems unlikely that very many of us would want to or be able to do that.
Just wondering.
Paul, N6PUD
Beaverton, Oregon
Joe Braswell
The latest "school of thought" is: If you want to preserve your
equipment, disconnect EVERYTHING when not in use. This means power,
ground, interconnects, etc.
Just what I have been reading lately.
joe
Gary Coffman
The NEC says to maintain at least a 5 foot separation from any other
conductors to prevent sideflash. Since the ground window is bonded
to the Earth terminal, which is in turn bonded to all other system
grounds, including the power entrance ground, the potential between
your station wiring and *unused* existing electrical wiring should be
sufficiently low to work with the NEC recomended 5 foot separation.
You shouldn't need to rip it out of the walls. Just don't plug anything
in the station into it.
Paul Silva
Joe Braswell wrote:
>
> [Deletia]
>
> The latest "school of thought" is: If you want to preserve your
> equipment, disconnect EVERYTHING when not in use. This means power,
> ground, interconnects, etc.
> Just what I have been reading lately.
> joe
I think what you've been reading is the "cheapskate's guide to better
lightning protection".
What is an individual going to do, pile all of their cables and
equipment in the middle of the room every time a storm approaches or
when they aren't going to be using it for a day or two? I'd rather
protect my home, person, and property by installing a properly
designed grounding and lightning protection system. The "disconnect
everything when not in use" method has never sounded like much of
lightning protection solution to me.
Getting back to my question about the shack wiring...If the induced
energy from a lightning strike can travel through the house wiring
and jump from the wall socket to damage nearby equipment, in a perfect
grounding world, shouldn't the normal house wiring be taken out of
the shack, and only the AC coming from the single ground point be
used?
Any thoughts about this?
Paul, N6PUD
Paul Silva
Gary Coffman wrote:
>
> The NEC says to maintain at least a 5 foot separation from any other
> conductors to prevent sideflash. Since the ground window is bonded
> to the Earth terminal, which is in turn bonded to all other system
> grounds, including the power entrance ground, the potential between
> your station wiring and *unused* existing electrical wiring should be
> sufficiently low to work with the NEC recomended 5 foot separation.
> You shouldn't need to rip it out of the walls. Just don't plug anything
> in the station into it.
Thanks Gary. This is what I was fishing for.
The NEC code information mentioned above sounds great in theory, but
I'll
wager that regardless of where their station power is coming in from, an
overwhelming percentage of hams have their equipment desks and tables
set
up against a wall 2 or 3 feet from the nearest outlet. Of course, an
overwhelming percentage of hams are probably not addressing the
grounding
issue correctly anyway, but that's another story.
In most modern dwellings I think it is safe to assume that the average
room will have 3 or 4 outlets, along with the associated wiring in the
wall, naturally. To bring power lines from the single point ground into
the shack without coming near the wiring in the walls and to place the
station's equipment out of harm's way as well, sounds like a difficult
(if not impossible) task for most of us.
If the wiring is left in, I'd hope that the "sufficiently low" potential
stays sufficiently low. However, if it is possible without too much
trauma
to the house, I might be inclined to "uninstall" the wiring anyway. It
might also be possible to take the wiring out and leave a string or line
in its place to make putting the wiring back a bit easier. A lot would
depend on the construction of the house, of course.
As I said before, I'm planning my station and ground system, gathering
materials, etc., and I've been giving this topic a lot of thought.
Paul, N6PUD
Bob Bethman
Paul Silva wrote:
Paul,
Since the power STILL comes from the service entrance panel you have
not isolated it. You still bring the power lines AND ground to your shack.
There is a point of diminished return. You CANNOT achieve complete
isolation unless you provide your own power source, i.e., generator.
--
Phase 1 \\"""// 4-1000A Amplifier \\"""// Ongoing
(@ @) (Building in progress) (@ @)
+-------oOOo-(_)-oOOo-----------------------oOOo-(_)-oOOo-------+
| Amateur Radio Operator N0DGN/4 -- Northern Virginia |
+---------------------------------------------------------------+
| Bob Bethman \\\|/// " Mistakes are a fact of |
| N0DGN/4 \\ ~ ~ // life, It is the response |
| rbet...@erols.com (/ @ @ /) to the error that counts"|
+-------.oooO---Oooo.-----oOOo-(_)-oOOo------.oooO---Oooo.------+
( ) ( ) Home of the ( ) ( )
\ ( ) / New \ ( ) /
\ _) ( _/ "Sasquatch" \ _) ( _/
Joe Braswell
I understand what you are trying to achieve and I have read the other
threads and I agree with the National Electrical Code guidelines. You
really have to protect your property by following these guidelines.
The point I'm making about the disconnect is if you take a direct hit
then nothing is going come out unscathed. If you have a $4000 set up or
more then it probably wouldn't hurt to isolate it via total disconnect.
For the "near misses" then the guidelines identified in NEC will do
wonders. I'm trying to think of a lightning product catalog that I saw
once which had a lot of GOOD application notes. If I can think of it I
will pass it along.
joe
Paul Silva
Bob Bethman wrote:
>
> Paul Silva wrote:
>
> > Gary Coffman wrote:
> > >
> > > should be star connected. External to the station, everything star
> > > connects to your ground field single point. Internal to the station,
> > > everything star connects to the ground window. These two are tied
> > > together with a heavy low inductance strap.
> > >
> > > It is absolutely essential that no wiring bypass this system. If even one
> > > wire bypasses the system, all of the protection it offers you is lost. The
> > > use of a ground window and a single point are central to good lightning
> > > protection. There are other steps you have to take too in order to be
> > > able to operate during a storm, but these two steps are essential.
> >
> > There is one thing I've never seen mentioned in all the literature I've
> > read about lightning protection both in the newsgroups and elsewhere.
> >
> > As I get ready to construct my station and ground system, I'm wondering
> > what one should do about the AC wiring that is already in place in the
> > room they are going to use as their shack. I'm sure that 99.9% of us
> > will
> > have our shacks in a room in our residence. That room will already be
> > wired for 120 VAC and it won't be going through any "single ground
> > point."
>
> andgrounds indeed DO go through a "single ground point." ALL neutrals,
> (white wires), go back to the service entrance panel and are bonded on a bus.
> All green (or bare) grounds also go back and terminate in a bus. This is your
> single ground point. You may take a heavier copper conductor back to the
> panel and bond it also providing another path.
You are referring to the electric company's ground and not to "THE"
single point ground. If we subscribe to the "star pattern" method of
tying grounds together, the electric company's ground is is just one of
many (telco, catv, towers, ground window) that gets wired into the
single point ground.
My question (which Gary addressed) focused on what to do with the normal
house wiring in the shack that was not being used to power the station's
equipment. It is true these lines are connected to the electric
company's ground back at the entrance panel, but since they are not tied
into the ground window from the shack, an induced charge from a nearby
lightning strike could still possibly damage equipment near the outlets
via sideflash. That was my only question...what to do about the unused
wiring.
Paul, N6PUD
Bob Bethman
Paul Silva wrote:
> Bob Bethman wrote:
> >
>
> > If your home was built within about the last twenty years, ALL neutrals
> > andgrounds indeed DO go through a "single ground point." ALL neutrals,
> > (white wires), go back to the service entrance panel and are bonded on a bus.
> > All green (or bare) grounds also go back and terminate in a bus. This is your
> > single ground point. You may take a heavier copper conductor back to the
> > panel and bond it also providing another path.
>
> You are referring to the electric company's ground and not to "THE"
> single point ground. If we subscribe to the "star pattern" method of
> tying grounds together, the electric company's ground is is just one of
> many (telco, catv, towers, ground window) that gets wired into the
> single point ground.
>
> My question (which Gary addressed) focused on what to do with the normal
> house wiring in the shack that was not being used to power the station's
> equipment. It is true these lines are connected to the electric
> company's ground back at the entrance panel, but since they are not tied
> into the ground window from the shack, an induced charge from a nearby
> lightning strike could still possibly damage equipment near the outlets
> via sideflash. That was my only question...what to do about the unused
> wiring.
>
> Paul, N6PUD
Paul,
My point is that the "ground window" really introduces ANOTHER ground system.
You are still pulling power from the original service entrance panel. You are
now providing secondary paths. Even when you remove the unused wiring
in the shack, you can and will get induced carryover into the shack with a very
near or direct strike. If the entire grounding system of the house AND the shack
are done properly the VERY best you can do is limit the damage.
If the strike is near enough, or if it is direct, you cannot protect the shack
entirely.
The best that can ever be done is to limit the damage.
The biggest mistake folks make is the size of the grounding conductors, and their
layout/path. Make any bends with a LARGE radius. Use #2 or #4 conductors
for the shack ground as a MINIMUM.
Bob Bethman
Paul Silva
From what I've read, two points about "ground windows" have become
clear:
1) It should be the point through which all the shack's wiring is routed
(and bonded).
2) It should be connected to an "earth terminal" which is at the center
of all of the legs of a star pattern (no daisy chaining or loops). This
provides dissipation paths for, and equalization of, voltage potentials
harmful to equipment (or you).
Using a ground window doesn't appear to me to be introducing another
ground system, but rather a new, necessary leg of an overall ground
system. Are you suggesting that the ground window approach is wrong?
> Even when you remove the unused wiring
> in the shack, you can and will get induced carryover into the shack with a very
> near or direct strike. If the entire grounding system of the house AND the shack
> are done properly the VERY best you can do is limit the damage.
These are truisms that apply to any station's grounding system.
> If the strike is near enough, or if it is direct, you cannot protect the shack
> entirely.
> The best that can ever be done is to limit the damage.
Agreed. That is what I'm trying to do, limit the damage.
> The biggest mistake folks make is the size of the grounding conductors, and their
> layout/path. Make any bends with a LARGE radius. Use #2 or #4 conductors
> for the shack ground as a MINIMUM.
Yes, every piece of literature about grounding mentions not having any
sharp bends in the grounding conductors. That creates more inductance
and more resistance...just what you don't want in a ground system.
I have already purchased a large roll of #4 solid copper wire for
bonding the grounds together. In addition, I went to some local scrap
metal yards and picked up all sorts of interesting pieces of copper
flashing, buss bar, connectors, etc. My timing was good enough one day
to snag a large (45" x 80") piece of copper sheeting. I envision using
this piece to construct a "ground window box" with plenty of room to
mount the surge protection devices for the AC, antenna, rotator/remote
RF switch lines, etc., on their way to the shack.
Paul, N6PUD
Jim Berry K7SLI
Paul Silva <psi...@teleport.com> wrote in article
<355557...@teleport.com>...
> Joe Braswell wrote:
> >
> > [Deletia]
> >
> > The latest "school of thought" is: If you want to preserve your
> > equipment, disconnect EVERYTHING when not in use. This means power,
> > ground, interconnects, etc.
> > Just what I have been reading lately.
> > joe
>
> I think what you've been reading is the "cheapskate's guide to better
> lightning protection".
>
> What is an individual going to do, pile all of their cables and
> equipment in the middle of the room every time a storm approaches or
> when they aren't going to be using it for a day or two? I'd rather
> protect my home, person, and property by installing a properly
> designed grounding and lightning protection system. The "disconnect
> everything when not in use" method has never sounded like much of
> lightning protection solution to me.
>
> Getting back to my question about the shack wiring...If the induced
> energy from a lightning strike can travel through the house wiring
> and jump from the wall socket to damage nearby equipment, in a perfect
> grounding world, shouldn't the normal house wiring be taken out of
> the shack, and only the AC coming from the single ground point be
> used?
>
> Any thoughts about this?
>
> Paul, N6PUD
>
And then I ad: I can see it now, here is this guy running around
disconnecting everything while he takes a lightning strike. Poof. Sounds
like the last thing I would want to be doing during a lightning storm is
tossing antenna feedlines out the window.
I am following this tread real close also. I am also wiring up a separate
radio shack in my backyard. I will have my gear running during any
lightning storm. The commercials do, so why can't a ham?
73 Jim K7SLI
Paul Silva
Jim Berry K7SLI wrote:
>
> [Deletia]
>
> And then I ad: I can see it now, here is this guy running around
> disconnecting everything while he takes a lightning strike. Poof. Sounds
> like the last thing I would want to be doing during a lightning storm is
> tossing antenna feedlines out the window.
Yes, besides the absurdity of all the running around and disconnecting
things, there is that small matter of DYING while doing it. :)
> I am following this tread real close also. I am also wiring up a separate
> radio shack in my backyard. I will have my gear running during any
> lightning storm. The commercials do, so why can't a ham?
This sounds like the way to go, if one has the room. A seperate
building designed from the ground up (so to speak) that optimizes the
functionality of a ham shack. Good luck with it!
Paul, N6PUD
Gary Coffman
>in the shack, you can and will get induced carryover into the shack with a very
>near or direct strike. If the entire grounding system of the house AND the shack
>are done properly the VERY best you can do is limit the damage.
>
>entirely. The best that can ever be done is to limit the damage.
This is *NOT* true. It is not only possible, it is routinely feasible to sustain
multiple direct strikes without sustaining *any* damage to your equipment.
Every commercial broadcast station does it during every thunderstorm.
They don't survive due to good luck, they survive due to good engineering.
And a key part of that good engineering is the ground window (that name
is really a misnomer, keep in mind that Earth and ground are rarely the
same thing even though in common language they are often used
interchangeably).
A properly installed ground window equalizes the potentials on all cabling
exiting or entering the protected area. This is the key concept to protecting
against strikes. There is no such thing as "the" ground potential when you're
dealing with lightning. What the ground window does is establish *a* common
potential for all cabling entering and leaving the protected area. As long as
that is done, we don't care very much what potentials might exist to various
connections to Earth at various other locations.
We only care about that to the extent of preventing sideflashes. As the NEC
recomends, a 5 foot separation is normally desired between a fully lightning
energized conductor and any other conductor. By snubbing these conductors
to Earth, we can reduce the sideflash potential to manageable levels which
can reduce that distance. In dry air, it takes 10,000 volts per inch to breakdown
air and allow a sideflash. If we could keep the potential difference between two
separately earthed systems down to 10,000 volts, we would only need a
separation of 1 inch. Generally we can't do that due to the inductance of the
various conductors and the difference in their Earth terminal potentials, so
we want a larger separation. But we don't need the full 5 five feet as long as
the inductance in the differential path is kept relatively low.
The ground window itself is normally snubbed to Earth with as low an
inductance conductor as we can arrange. This is done primarily for
personnel protection. A ground window can work even if it is fully
floating, but the entire station will elevate to a very high potential
with respect to Earth during a strike in that case. That's fine as far
as the equipment is concerned since all of it elevates to the *same*
potential. (It is potential *difference* that matters, there actually is
no such thing as absolute potential). But it is not fine for things not
connected to the ground window. The potential to Earth can be high
enough to allow a sideflash to personnel wandering around in the
protected area, or to other things which aren't being held to the
same potential. So we snub the ground window to Earth as well
as possible to reduce this hazard. (Realize that by design we provide
no other path to Earth for equipment grounds *except* via the ground
window.)
We also reduce the potential to Earth at the ground window by providing
lightning with *another path* to Earth. We don't really want the ground
bond at the ground window to handle the entire strike current (though we
should size it so that it could). We want the bulk of the strike current to
find its way to Earth via another path *outside* the protected area.
We do that for antennas by providing a direct path to Earth from them.
Towers are bonded to the station radial ground field at their bases. That's
the lowest inductance path for the lightning current in a tower strike, and
most of it will take that path rather than the path over to the station ground
window and its connection to Earth. (The paths are in shunt, and the lower
inductance path hogs the current.) Now the potentials involved in a strike
can be staggering, and the currents are huge, so even with this shunt, the
ground window still is needed. But we've substantially reduced the work it
must do to provide protection.
Similarly, we depend on the suppression at the power service entrance
to give us some relief from strike surge coming in on the power lines,
and the same for strikes to telephone lines. It is a good practice to
install a whole house suppressor at the service entrance panel rather
than depending on sideflash between the nominally hot service conductors
and the nominally grounded service buss and panel housing. Gas tubes are
best, but silicon carbide suppressors can be used instead if you expect
no more than one strike per storm (silicon carbide suppressors are one
shot protectors, you have to replace them after they fire). This won't do
the whole job because of the finite impedance of the service entrance
connection to Earth, but it will reduce the load on the suppression at the
station ground window.
The phone company installs a suppressor, carbon blocks in the old days,
gas tubes today, at the telco service entrance. This helps by shunting some
of the strike current to the telco earth terminal, usually a made electrode
(ground rod). But the lines will still be elevated with respect to Earth by an
amount determined by the impedance of this Earth connection and strike
total current (Ohm's Law). It helps, but not enough. We still must bond telco
lines coming into the shack to the ground window.
We also want to equalize the potentials between the various Earth terminals
as best we can. They won't be the same due to the finite impedance of the
paths through Earth between each of them. In fact, Earth currents during
a strike are huge, and can elevate the potential of earth terminals which
aren't even directly involved in handling the strike current. So we star connect
all of the Earth terminals to a single point. This establishes a point of common
potential for all of the Earth terminals. This is the point where we bond the
station ground window to Earth. That bond will then only have to carry the
current driven by the difference in *average* potential between the conductors
bonded to the ground window and the *average* potential of all the various
Earth terminals in the system. This reduces the load on this bond, and
reduces to the maximum amount possible the average elevation of station
potential above Earth, thus reducing as much as possible sideflash risks.
The ground window should be our *last* line of defense, not the first. We
want to knock down as much of the lightning surge as possible before
reaching it. Multiple Earth connections *outside* the ground window
are a strong advantage in this regard (they are death inside the ground
window). We want them, and we want them to have as low an impedance
as possible. In that regard, we want to use the best Earth terminal techniques
possible. Ufer grounds are one such. If you have one, use it. If you don't
have one, consider installing one. Rebar in concrete is a better Earth
terminal than virtually anything else you can provide. Ground rods are
about the worst Earth terminals that are still useful. Plan accordingly.
The NEC *requires* all Earth terminals to be bonded together. Do it,
but do it with the proper circuit topology.
Station layout, antenna systems layout, ground field layout, etc all play roles
in the total system protection design. We want all of that to be in star, and
stars of stars, topology. Avoid at all costs use of daisy chains and buss
layouts. They are sure producers of ground loops which will contain vulnerable
equipment. The purpose of using star topology is to *short out* any ground loops
that may exist in each subsystem so that equipment won't be contained in
the loop.
And always remember that lightning is *RF*. Different length paths will have
different phases due to transmission line effects. Maintain symmetry and
balance to avoid problems caused by this. And inductance is our chief enemy.
We need to minimize it as much as possible in any lightning current path to limit
the potential developed across that path. We're dealing with peak current flows
of 18,000 amperes, and the frequencies in the lightning discharge extend into
UHF, so it doesn't take much inductance to develop very high potential differences.
(Fortunately, the bulk of strike energy is contained in frequencies below 2 MHz.
If it were evenly distributed across the spectrum, our task would be much harder.)
We can't prevent lightning strikes, but we can control the effects of a strike
by using sound engineering practices. Lightning is no different from any other
RF current (except in magnitude). The same electrical laws we use for RF
currents work for lightning currents too. Just model the discharge as an 18,000
ampere constant current source backed by virtually unlimited cloud to Earth
potential. (The discharge behaves as a current source due to the characteristics
of the plasma tube conducting it.) Since we can count on a fixed current, we
can determine the potential between any two points by simple application of
Ohm's Law (and Kirchhoff's laws for multiple branch paths). It is just like any
other RF circuit. The duration of a lightning stroke is approximately 12
microseconds, so we can also determine the amount of energy a given
impedance path must be designed to handle to avoid damage. The only
things that should be unfamiliar to us are that the discharge is broadband,
and that its magnitude is larger than we are accustomed to handling.
Gary Coffman
On Thu, 23 Apr 1998 20:36:11 -0400, N1IIC <n1...@qsl.net> wrote:
> Frank Finger, NU1A, had written an article about lightning how's and
>why's of strikes.
> Have you ever seen the lightning rods on the top of the older type
>(mostly victorians and barns) buildings? Well, those don't attract
>lightning, they dissipate the charge before it can build up.
Oh dear, that is *NOT* true. Ben Franklin must be rolling over in his grave.
Franklin invented the lightning rod, and as he well understood, you cannot
prevent lightning, you can only control the discharge. Lightning rods do
that by becoming the *preferred target* for the discharge. Since they are
*designed* to handle it safely, no harm is done to the structure on which
they are mounted.
>See, lightning
>doesn't start in the clouds, it meets a 'feeder' from the ground. if there
>is no feeder, there is no strike.
That's half true. The lightning discharge follows the lowest
impedance path between cloud and Earth. Typically that's formed
when a step leader descending from the cloud meets a streamer
coming up from the Earth. The streamer isn't *mandatory*, but it
usually does exist because the mirror charge in the Earth is as
strongly attracted by the charge in the cloud as the charge in the
cloud is attracted to Earth.
> That is explained by the quote from his article;
>
> "While reexamining one of my old physics books, I came across a formula
>for the discharge from a sphere. My attention was attracted to the following
>sentences. "It has been previously shown that the maximum charge that can be
>retained by a conductor in air is limited by the fact that the air itself
>becomes conducting at an electric intensity of about 3 x 10>6 volts per
>meter. Vm=a*Em. Em is the maximum voltage; and, a is the radius of the
>sphere. For a sphere one centimeter in radius, Em=30,000 volts, and no
>amount of "charging" can raise the potential of a sphere this size, in air,
>higher than 30,000 volts."
That's true enough, but what is left out is what happens when the potential
exceeds that threshold, as it *will* in a thunderstorm. What happens is
streamer formation. You can't prevent it. It is driven by the many millions
of volts potential between cloud and Earth.
> And we all know that lightning carries a much greater voltage than
>30,000.
Yes it certainly does, so even a spherical conductor will break into
streamer formation. In fact, lightning rods are sharply pointed. This
allows them to break into streamer formation at a lower potential.
By streaming early, before other structures in the area break into
streamer formation, they become the preferred lightning targets.
That's their job.
> Thus, if you were to install an inverted spear that is well grounded
>above your installation, there will be no strike in about a 50ft radius.
Nonsense, and a total misunderstanding of the physics of lightning.
A lightning rod does offer a cone of protection around it, but not by
*preventing* strikes. It offers the protection by *taking* the strike
itself. It assures that by being designed to break into streamer
formation before surrounding structures do, and thus making itself
the preferred path for the lightning discharge. Franklin proved this
over 200 years ago.
This should be well covered in any electrical text documenting the
history of science. Franklin's invention was a major milestone in
electrical science, and a great boon to humanity. Before Franklin's
understanding of the lightning discharge, man was at the mercy of
lightning. It seemed a sign of divine wrath (though amusingly, it
struck church steeples most often). Franklin showed it to be
mundane electricity, and subject to man's control by application
of the laws of science. This was a major triumph of the Age of
Reason. I'm appalled that there is so much ignorance and myth
surrounding this subject, especially by those in a supposedly
technical avocation.
Gary Coffman
On Sun, 10 May 1998 08:22:49 GMT, Paul Silva <psi...@teleport.com> wrote:
>If the wiring is left in, I'd hope that the "sufficiently low" potential
>stays sufficiently low. However, if it is possible without too much
>trauma
>to the house, I might be inclined to "uninstall" the wiring anyway. It
>might also be possible to take the wiring out and leave a string or line
>in its place to make putting the wiring back a bit easier. A lot would
>depend on the construction of the house, of course.
Your other option is to simply bond the unused wiring to the ground
window. That'll assure it will be at a low enough potential not to
side flash.
Paul Silva
Gary Coffman wrote:
>
> On Sun, 10 May 1998 08:22:49 GMT, Paul Silva <psi...@teleport.com> wrote:
> >If the wiring is left in, I'd hope that the "sufficiently low" potential
> >stays sufficiently low. However, if it is possible without too much
> >trauma
> >to the house, I might be inclined to "uninstall" the wiring anyway. It
> >might also be possible to take the wiring out and leave a string or line
> >in its place to make putting the wiring back a bit easier. A lot would
> >depend on the construction of the house, of course.
>
> Your other option is to simply bond the unused wiring to the ground
> window. That'll assure it will be at a low enough potential not to
> side flash.
Maybe you could clarify something. Are you talking about bonding the
"live" unused wiring (like you would the station AC through suppression
devices) at the ground window, or are you referring to the bonding of
wiring that is still under the house and in the walls that has been "cut
off" from the rest of the house, but is still susceptible to induced
energies? I suppose if it were the latter case, the other end(s) of the
unused wiring would have to be grounded too. That might be difficult to
do effectively.
Also, there could be a lot of unused wiring to account for in the
average room. It seems like you could end up with a lot of extra wire
strung about. I'm a minimalist when it comes to ham shack wiring. The
more extraneous wiring you have, the more problems it could introduce.
Even though my first inclination would be to remove the wiring, there is
certainly no guarantee that it would even be possible. Doing as you
suggest might be the only realistic choice in many situations, as long
as it was possible to be able to observe the "5 foot" rule whenever
wiring couldn't be accounted for.
In case some of you following this thread are wondering, there IS a
reason that I might seem to be a little "wierded out" about this topic.
Although I've been a ham for over 20 years, I've been out of the hobby
and without equipment for the past several. I've decided to get back
into it in a big way. I even upgraded (finally!) from general to extra
in anticipation of getting back on the air. My point here is that I've
spent a good chunk of change recently on equipment (new and old), and
I'd like to ensure that it (and me) are around for a while to enjoy it.
:^)
Paul, N6PUD
Gary Coffman
On Wed, 13 May 1998 02:28:53 GMT, Paul Silva <psi...@teleport.com> wrote:
>Gary Coffman wrote:
>>
>> On Sun, 10 May 1998 08:22:49 GMT, Paul Silva <psi...@teleport.com> wrote:
>> >If the wiring is left in, I'd hope that the "sufficiently low" potential
>> >stays sufficiently low. However, if it is possible without too much
>> >trauma
>> >to the house, I might be inclined to "uninstall" the wiring anyway. It
>> >might also be possible to take the wiring out and leave a string or line
>> >in its place to make putting the wiring back a bit easier. A lot would
>> >depend on the construction of the house, of course.
>>
>> Your other option is to simply bond the unused wiring to the ground
>> window. That'll assure it will be at a low enough potential not to
>> side flash.
>
>Maybe you could clarify something. Are you talking about bonding the
>"live" unused wiring (like you would the station AC through suppression
>devices) at the ground window, or are you referring to the bonding of
>wiring that is still under the house and in the walls that has been "cut
>off" from the rest of the house, but is still susceptible to induced
>energies? I suppose if it were the latter case, the other end(s) of the
>unused wiring would have to be grounded too. That might be difficult to
>do effectively.
Simply disconnect the hot wire from the breaker in the entrance panel
and attach it to the ground bond in the panel. All you've effectively done
is add another ground bond between power ground and your system
ground. Since that is *electrically* outside the ground window, that's
acceptable, IE it is electrically tangental to the protected area. Potentials
between this wiring and other wiring attached to the ground window should
now never exceed reasonable sideflash potentials.
>Also, there could be a lot of unused wiring to account for in the
>average room. It seems like you could end up with a lot of extra wire
>strung about. I'm a minimalist when it comes to ham shack wiring. The
>more extraneous wiring you have, the more problems it could introduce.
That's true. Ideally, you would remove the stray wiring. What I'm offering is
a compromise alternative that is safe if not elegant. It may cause RF problems,
however. That can't be determined until the details of your antenna systems
are known.
>In case some of you following this thread are wondering, there IS a
>reason that I might seem to be a little "wierded out" about this topic.
>Although I've been a ham for over 20 years, I've been out of the hobby
>and without equipment for the past several. I've decided to get back
>into it in a big way. I even upgraded (finally!) from general to extra
>in anticipation of getting back on the air. My point here is that I've
>spent a good chunk of change recently on equipment (new and old), and
>I'd like to ensure that it (and me) are around for a while to enjoy it.
There is more to be done, and now is the time to do it. Besides the
ground window we've discussed at length, and besides the treatment
of your Earth terminals to form an effective ground field, there are
other matters of layout to be considered. For example, do not use an
aerial swing for your coaxes off the tower over to the station. Bring them
all the way down to the ground and bond them there before bringing them
to the station.
If you come off the tower at the 10 foot level, and assuming the tower
is Rohn 25, there is enough inductance in that section that during a
tower strike your coax shields will be elevated by at least 10 kV. That's
not nice to bring to the station. By bringing the coaxes down to the
tower base first, you can short out that inductive drop. You also short
out the single turn transformer formed by the tower and the coax.
That too can induce surge on your cables.
As I've said many times, details matter in this sort of thing. Some of
the details are not obvious. And some of the things which might look
like a good idea, aren't, when you examine them closely. The ideal
would be to have an on-site analysis performed by a lightning mitigation
specialist. But that can be expensive, and there aren't that many
qualified lightning mitigation specialists in the country, and not all
of them are familiar with the unique problems of amateur radio
installations anyway.
The lightning discharge is a complex phenomena, but if you take the
time to analyze it with respect to protective measures, it isn't that
complex. Just keep in mind you are dealing with a broadband RF
constant current source of about 18 kiloamperes and model
accordingly. You can't fight it, you have to work with it, and guide
it so that it doesn't have adverse effects on your installation.
Paul Silva
This would work fine as long as the hot wire you are moving over is from
a circuit that is dedicated to the room in question. I'm no
electrician, but I think most bedroom wiring circuits are wired in
series with another room or two. There might be seperate wiring for the
dryer, kitchen, family room, etc., but I doubt there is a seperate
circuit brought to the entrance panel for EVERY room in the house. I
don't think that would be too cost effective from a wire usage point of
view. That's why I'm thinking I'd have to get under the house and trace
the wiring that goes to the part of the house where the ham shack is to
go and hope that it's the last in the series and not the first.
> >Also, there could be a lot of unused wiring to account for in the
> >average room. It seems like you could end up with a lot of extra wire
> >strung about. I'm a minimalist when it comes to ham shack wiring. The
> >more extraneous wiring you have, the more problems it could introduce.
>
> That's true. Ideally, you would remove the stray wiring. What I'm offering is
> a compromise alternative that is safe if not elegant. It may cause RF problems,
> however. That can't be determined until the details of your antenna systems
> are known.
Yes, its the RF problems that I'm trying to minimize as well. Can you
say "re-radiation" or "stray RF"? As far as the antenna systems go, I'm
going to be putting up a tower and a 6 band quad. There will be at
least one other antenna hanging off the tower and maybe two. I'll also
have a R7000 installed somewhere away from the tower. Between the coax
lines, control lines, rotator lines, power lines, ground lines...yada
yada yada, there's lots of stuff to account for, but that's why I'm
trying to address the issues now and not after the fact.
> >In case some of you following this thread are wondering, there IS a
> >reason that I might seem to be a little "wierded out" about this topic.
> >Although I've been a ham for over 20 years, I've been out of the hobby
> >and without equipment for the past several. I've decided to get back
> >into it in a big way. I even upgraded (finally!) from general to extra
> >in anticipation of getting back on the air. My point here is that I've
> >spent a good chunk of change recently on equipment (new and old), and
> >I'd like to ensure that it (and me) are around for a while to enjoy it.
>
> There is more to be done, and now is the time to do it. Besides the
> ground window we've discussed at length, and besides the treatment
> of your Earth terminals to form an effective ground field, there are
> other matters of layout to be considered. For example, do not use an
> aerial swing for your coaxes off the tower over to the station. Bring them
> all the way down to the ground and bond them there before bringing them
> to the station.
I have already been to the scrap metal yard and picked up several blocks
of aluminum to be fashioned into grounding blocks for the coax and
control line shields at the base of my aluminum tower. I also purchased
some penetrox A-13 joint compound to keep the dissimilar metals happy.
> If you come off the tower at the 10 foot level, and assuming the tower
> is Rohn 25, there is enough inductance in that section that during a
> tower strike your coax shields will be elevated by at least 10 kV. That's
> not nice to bring to the station. By bringing the coaxes down to the
> tower base first, you can short out that inductive drop. You also short
> out the single turn transformer formed by the tower and the coax.
> That too can induce surge on your cables.
I've been reading a lot about this sort of thing from Polyphaser and
other sources. I know better to be stringing coax or other lines at
random.
> As I've said many times, details matter in this sort of thing. Some of
> the details are not obvious. And some of the things which might look
> like a good idea, aren't, when you examine them closely. The ideal
> would be to have an on-site analysis performed by a lightning mitigation
> specialist. But that can be expensive, and there aren't that many
> qualified lightning mitigation specialists in the country, and not all
> of them are familiar with the unique problems of amateur radio
> installations anyway.
Yeah, the on-site analysis by the specialist might be a bit of a stretch
in most circumstances. Especially for the average ham. I don't claim
to be an expert, but I'd like to think I have some idea of what I'm
doing. :) Of course, it couldn't hurt to bring in another pair of eyes
to check things out.
> The lightning discharge is a complex phenomena, but if you take the
> time to analyze it with respect to protective measures, it isn't that
> complex. Just keep in mind you are dealing with a broadband RF
> constant current source of about 18 kiloamperes and model
> accordingly. You can't fight it, you have to work with it, and guide
> it so that it doesn't have adverse effects on your installation.
I have no plans to fight it, that's for sure. The surge/transient/rfi
devices I'm designing do take into account the wide spectrum of
frequencies that lightning generates. Since much of the energy is
around 1 Mhz, that is where I try to maximize my blocking efforts. I am
also addressing HF/VHF energy in the secondary stages of the filters.
If all the grounding materials can just dissipate most of the energy,
I'm hoping that my devices will be able to account for the rest.
Paul, N6PUD
Reg Edwards
Franklin was right. But how much of his reasoning about lightning
conductors was based on a knowledge of propagation of electrical transients
along transmission lines (LCRG) and how much on intuition ?
The years when he did his work may provide a clue. How does he interleave
with Ohm, Faraday, Henry ?
He is not so well known over here. Perhaps because the infliction of
thunder storms is much less severe.
--
Reg G4FGQ
http://www.btinternet.com/~g4fgq.regp
Steve
Reg,
Perhaps he is not so well known over there for ppolitical reasons?
He was one of the drafters and signers of the American Declaration of
Independence and was an American agent in France during our
Revolutionary War against Britain.
No offence intended, Reg! That was over 200 years ago!
73
Steve, N4EY
Reg Edwards
>> Steve wrote :-
>> He was one of the drafters and signers of the American Declaration of
>> Independence and was an American agent in France during our
>> Revolutionary War against Britain.
>>
>> No offence intended, Reg! That was over 200 years ago!
Of course not Steve.
I understand Franklin was an eccentric fellow whose favorite pastime was
defying the laws of probability by strolling around the open countryside in
the middle of thunderstorms while flying a kite.
Since these experiments were conducted more than 200 years ago I would
think our modern lightning conductors owe much, not only to his sound
intuition, but also to his extraordinary good luck.
Reg.
Gary Coffman
On 14 May 1998 07:16:51 GMT, "Reg Edwards" <g4fgq...@btinternet.com> wrote:
>Franklin was right. But how much of his reasoning about lightning
>conductors was based on a knowledge of propagation of electrical transients
>along transmission lines (LCRG) and how much on intuition ?
>
>The years when he did his work may provide a clue. How does he interleave
>with Ohm, Faraday, Henry ?
>
>He is not so well known over here. Perhaps because the infliction of
>thunder storms is much less severe.
Franklin lived from 1706 to 1790. He was a publisher, statesman, and
scientist. It is surprising you haven't heard of him. He was elected
a fellow of the Royal Society for his scientific achievements. Your
Willian Pitt said that Franklin ranked with Issac Newton as a scientist.
Besides his work with electricity and the invention of the lightning rod,
he invented bifocal glasses, he invented the Franklin stove which is 8
times more efficient than a simple firebox stove, he charted the Gulf
Stream, he demonstrated that seas could be calmed by pouring oil on
them, etc, etc, etc. He is also the inventor of daylight savings time.
As civic leader, he created the US post office and is responsible for the
system of post roads which shaped our roadway development. He started
the US public library system, founded the University of Pennsylvania,
and served as ambassador to France. As publisher, his Poor Richard's
Almanac was the most widely read publication in early America.
Franklin's portrait is on our $100 bill, the only non-president so honored.