Well said David,
Being in the cell phone construction and cell/broadcast tower industry for
a couple of decades I find a lot of local hams asking me about
grounds. How I get hit (as I have had) and the radios and everything
survives just like my customers. First the antenna doesn't most of the
time but the rest does and it's exactly what you just said. But most hams
I find shove one ground rod in the dirt and call that their "ground ring".
First it's not a ring of anything. Second they don't have it on the same
potential as the tower or their house that they radios are plugged into,
they have nothing protecting the coax and just the ground wire to the back
of the radio and this will "save the shack". NOT
If you want to create a ring, use many many rods, cad weld them together
and with the house ground and try to make everything under 5 Ohms max on a
Meggar. I know the normal ham doesn't have the ability to measure and
create all this with Buss bars connected to the ground ring and poly's on
all the coax bolted to the bars but they wanted into this hobby so it's
the price you have to pay or 1. Move to where there is no lightning or 2.
Unplug your radios and put them in the bathtub. (then it may hit the
roof). But keep the potential the same! Here is an old website buy you all
may find interesting.
http://www.radioandtrunking.com/downloads/motorola/R56_2005_manual.pdf
Dave n4zkf
e-mail: n4zkf@n4zkf.com
web: http://www.n4zkf.com
AR-Cluster node: 145.05 Mhz. or telnet://dxc.n4zkf.com:23
CC-Cluster node: 145.07 Mhz. or telnet://ccc.n4zkf.com:7373
Packet BBS: 145.05 Mhz.-14.098 Mhz. or telnet://bbs.n4zkf.com:6300
BPQ Node: 145.05 Mhz.-14.098 Mhz. (n4zkf-5)
SEDAN Node: 145.770 Mhz. (n4zkf-7)
N4ZKF/R 147.375 Mhz. Tone 103.5
>On 9/6/14 8:14 AM, "David Robbins" <k1ttt@arrl.net> wrote:
>
>>Most lightning actually begins with a negative charge accumulation in the
>>lower areas of a convective cloud. The negative charge in the cloud
>>repels
>>the electrons below it in the ground and man made things near it. There
>>is
>>nothing you can do to 'bleed off' this charge. Then in most cases a
>>negatively charged leader starts coming down from the cloud relatively
>>slowly, you don't see this one unless you have a special camera or track
>>the
>>radio noise it makes as it steps its way downward 50-100m at a time. as
>>it
>>approaches the ground the charge on the ground concentrates until it
>>causes
>>a breakdown in the air and an upward moving leader connects with the
>>downward moving one and then BOOM, you see and hear the current that
>>flows.
>>Since the electrons must flow through something to get to/from that
>>attachment point to the ground there will be large currents and hence
>>high
>>voltages between the attachment point and anything around it, including
>>the
>>ground... this is where everyone messes up, they stick a rod in the
>>ground
>>and call that 'ground' as if it is always a perfect sink for electricity.
>>In fact it is common for the 'ground' wire of high voltage power lines
>>to
>>be
>>hit, that is the wire above the power conductors that is attached to the
>>towers that are all 'grounded'... but in a good percentage of those hits
>>the
>>voltage of the 'ground' gets so high that it flashes over the insulators
>>to
>>the power conductors, this is called a backflash. Those insulators can
>>be
>>rated for 100's of kV or even into the MV range and can't withstand the
>>voltage on the grounded conductor... so how do you do it with your puny
>>cables and tiny insulators?? You don't let the voltage across the
>>insulation get that high by forcing everything in the house/shack to
>>change
>>voltage in step with the ground. That is really what lightning arresters
>>do, they usually don't take current off the center conductor to the
>>shield
>>of a coax unless perhaps it was a vertical antenna that was hit. In most
>>cases they are increasing the voltage on the center conductor to match
>>the
>>shield, or on the control wires to match the ground wire. that way when
>>the
>>current gets to the sensitive device that you are trying to protect the
>>ground and signal wires are near the same voltage (which could be MV
>>different than the distant earth) so there is no danger of causing
>>damage.
>>But let just one power lead not be protected and it will be the wire at a
>>drastically different voltage and will be the target for the infamous
>>backflashover, and whatever equipment is between it and the ground is
>>toast.
>>
>>David Robbins K1TTT
>>e-mail: mailto:k1ttt@arrl.net
>>web: http://wiki.k1ttt.net
>>AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>>
>>
>>-----Original Message-----
>>From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>>Bill
>>Winkis (KC4PE)
>>Sent: Saturday, September 06, 2014 11:50
>>To: 'Kenneth Goodwin'
>>Cc: towertalk@contesting.com
>>Subject: Re: [TowerTalk] G-2800DXA lightning damage
>>
>>Proper Grounding....????
>>
>>Can we agree that a static crash/lightning/begins with a positive charge
>>in
>>Mother Earth, whether it be your Air Conditioner compressor/your
>>vertical
>>antenna/your tower/and on......so whatever is being charged must have a
>>proper ground with a proper bleed off, or the charge will continue until
>>a
>>atmospherically provided path couples and then BOOM, lightning/damage to
>>whatever.
>>
>>SO ..if one provides a proper text book ground he will have no problem to
>>bleed off this charging he will have zero problem
>>
>>Read On...!!!!
>>
>>https://www.google.com/?gws_rd=ssl#q=lighning+glen+zook
>>
>>http://www.w8ji.com/station_ground.htm
>>
>>Take the time to read the below...especially PolyPhasers WHITE Papers
>>
>>http://www.smithspower.com/brands/polyphaser/services/media-library/white
>>-
>>pa
>>pers?page=2
>>
>>-KC4PE
>>http://www.kc4pe.com/amateurshack.htm
>>
>>
>>
>>
>>-----Original Message-----
>>From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>>Kenneth Goodwin
>>Sent: Friday, September 05, 2014 3:10 PM
>>To: towertalk@contesting.com
>>Subject: Re: [TowerTalk] G-2800DXA lightning damage
>>
>>Agree, disconnecting everything is the only reasonable means of
>>protection.
>>If your radio equipment is hooked to a power outlet and/or a computer,
>>those
>>connections will have to be disconnected also unless one feels confident
>>enough to have the power/network/Internet/telephone connections
>>protected.
>>Near field lightning hits which are the highest probability of occurring
>>for
>>most nominal station configurations, will result in two common scenarios.
>>They obviously induce large amounts of energy into antenna systems and
>>such
>>things as one's security system if it has long wired connection paths,
>>e.g.
>>window sensors on one loop. Near field hits will also bring the energy
>>right up the ground connections as the potential level of one's land is
>>raised with the hit (the reason for single point grounds). Don't rely on
>>your Internet provider even if they have what looks like a protection
>>device
>>in the cable. They just normally ground the shield connection if cable
>>Internet/TV/VOIP telephone is used. Same applies to one's telephone if
>>that
>>is another wired connection. Since disconnecting every secondary
>>connection
>>is difficult, having protection for all of those other 'connections' is
>>probably the next best step. Disconnecting one's antennas/control lines
>>is
>>still desirable regardless since the probability of one's antennas
>>conducting energy is > 0. One also needs to remember the impact of
>>today's
>>house insurance deductibles. Last thing I want to do with my house
>>insurance company is file a claim. It's why I use the ARRL Insurance
>>program for my most expensive radio equipment. For my secondary
>>connections, I use multiple UPS's for power, have a gas discharge device
>>in
>>my Comcast cable as it enters the house in addition to protection at the
>>network box interface. My TV/Internet cable runs above ground except for
>>the connection from the pole to the house where it runs underground as is
>>normally implemented by most cable companies. In the newer
>>neighborhoods,
>>underground utilities are worth every indirect penny it costs. I use
>>surge
>>protection for the AC power at the breaker box and telephone line
>>protection
>>(MOVs) at the line entrance to the house. I tried protecting the AC
>>power
>>at the pole but the electric company didn't like that even though I own
>>the
>>underground wire from the breaker box to the pole. They rightfully
>>demand
>>control for everything from the power meter back. I know I can't fool
>>Mother Nature even with my single point ground system since I have so
>>many
>>back doors. I realize the commercial people are able to do it, but they
>>start out with a fresh sheet of paper and can easily design adequate
>>lightning protection from the very beginning with a no exception single
>>point ground system. Ken K5RG
>>
>>------------------------------
>>
>>Message: 5
>>Date: Fri, 05 Sep 2014 07:40:21 -0600
>>From: Steve London <n2icarrl@gmail.com>
>>To: towertalk@contesting.com
>>Subject: [TowerTalk] G-2800DXA lightning damage
>>
>>
>>>I live in an area with high monsoon thunderstorm activity. I doubt that
>>>any
>>of the protection devices would > survive. I disconnect everything where
>>it
>>enters my radio shack.
>>
>>>Spencer W1GAK
>>
>>I live near Spencer, and 100% concur with his recommendation. Put a Jones
>>plug at the control box and keep it disconnected during the thunderstorm
>>season unless you are actually on-the-air. If you are using a computer
>>connection to the control box, disconnect that also.
>>
>>73,
>>Steve, N2IC
>>
>>_______________________________________________
>>
>>
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk@contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>_______________________________________________
>>
>>
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk@contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>_______________________________________________
>>
>>
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk@contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|