Re: Long OTA antenna feedline

On Sat, 10 Jun 2006 17:52:36 -0700, "rz" <rz@xxxxxxxxxxx> wrote:


"Gerry Wheeler" <gxwheeler@xxxxxxxxxxxxx> wrote in message
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"Wes Newell" <w.newell@xxxxxxxxxxxxxxxxxx> wrote in message
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On Sat, 10 Jun 2006 14:37:48 +0000, phil-news-nospam wrote:

I would think so, too. But the issue is that at least SOME of this line
must be fiber optic.

Why? Because you want it to cost $2000 instead of $200?

No, because he doesn't want the next lightning strike to get to the house.
I think the cost of the fried equipment on the hilltop would be a small
price to pay.

If every thing is properly grounded that shouldn't be much of a risk.
It may happen, but a good ground system should take care of it.

I have a 130 foot tower
http://www.rogerhalstead.com/ham_files/Tower26.htm
or http://www.rogerhalstead.com/ham_files/tower.htm for the whole
project.

I have 4 computers tied together with a hard wired Cat5e gigabit LAN.
My main computer and backup in this room are located about 25 to 30
feet to the right of that open door in the photo. The computer in the
shop is just to the left of that window in the shop. The Cat5e runs
within 10 feet of the base of that tower (To the right). The down
through the basement, up through the garage wall, across the ceiling,
down the other wall and underground to the shop makes it about a 130
foot run.

There are two UHF TV antennas on the tower at almost the same height
of 90 feet, but only the one pointing to the left (NW) shows well in
the photo. For about 20 to 30 feet the coax cables and Cat 5e run
together through the basement ceiling. ALL of the cables from the
tower including the TV coax run together for 75 to 80 feet inside
underground conduit. In addition the coax from the small dish for Dish
Network (not shown in photo) at 25 feet on the tower and those UHF TV
antennas run through that same conduit plus an additional 30 feet
diagonally across the basement and up to the receiver as well as the
TV in the basement. The shop and thus the computer out there are on a
different electrical feed than the house.

That tower takes about three direct hits by lightning each summer.
Maybe more according to my neighbors. At any rate I have been
operating this computer when the lightning stuck the tower. (cordless
keyboard and mouse on each computer). The lights blinked, the UPSs
squealed for about a second and switched back. The file transfer from
this computer to the shop wasn't interrupted long enough for the
connection to drop.

There was no damage to any of the TV or computer equipment in the
house. There is no lightning protection on the TV, AC line to TV and
satellite receiver, satellite dish, or TV antennas OTHER than the
coax shield is grounded to the tower at the base and where it comes in
the house as are the shields on the ham station coax cables.

I do lose one of the remote amps up at the TV antennas on average of
about once every two to three years. I've only replaced two so that's
not much on which to build an average.


I've read about at least one person who uses a short length of fiber in a
residential LAN just to electrically isolate the LAN from the WAN. It
sounds very effective to me.

Just remember any unterminated/grounded wire is just like an antenna
as far as the lightning is concerned.

Another alternative would be a short radio link. I'm not sure it has any
advantage over fiber, except it might be something that can go directly
into a TV without conversion if it's done right.
--
Gerry

This is nuts, really. Because of the long run, the inductance would be
high.
This high inductance makes it easy to limit the voltage as it enters the
house

With the exception that most lightening damage is from induced voltage
and not direct hits. A strike a mile away can induce as much as a
1000 volts per meter into a conductor.

Properly grounded at the tower and where the cable enters the house
*should* shunt any high voltages to ground.

with spark arrestors. Also, the cable should be buried. In this case any
voltage high enough to break down the insulation would arc over to the
earth.

Except the earth in general is a pretty poor conductor. That's why we
put in those 8' ground rods. Code here requires two at the electrical
service entrance.


There is absolutely no danger of a lightning strike damaging anything in the
home if the cable is buried.

I'm not sure I'd go quite that far, but burying AND grounding is good.
My ground system consists of 32, eight foot ground rods Cad Welded
(TM) to over 600 feet of bare #2 copper. OTOH I do have the
neighborhood lightning rod according to my neighbors and one in
particular who was looking right at the tower when it took a direct
hit. He was standing about 60 feet behind where I stood to shoot that
photo in the first link above.

One example: the tower took a number of strikes in rapid succession
last summer. The pole transformer across the road and two houses to
the north also took a hit as did a pine tree about 200 yards to the
East. The neighbor who was hooked to that transformer lost their VCR,
TV, Water Heater, and a lot of other equipment. The pine tree
literally exploded with 3 and 4 foot long pieces of it stuck in the
ground over 50 feet from the tree. I had no damage and I don't unplug
anything during thunderstorms, but I do have a very elaborate ground
system for the tower, antennas, and house. It's also quite possible I
have a lot of luck, but I've put a lot of planning into that system.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
.

Relevant Pages

  • Re: Lightning Question
    ... transmission line down from the antenna, bury the line, run it underground to the house, place a lightning arrestor and ground just outside the house, then run the transmission line up the side of the house to the operating position on the second floor. ... I can't imagine that a lightning would "want" to travel back up toward the operating position when it has a good ground closer to the antenna. ... you would be better to place a lightning arrestor at the tower (and ground ... The coax from the tower to the house has a directly clamped, not soldered, connection from the braid to a ground rod where it enters the house. ...
    (rec.radio.amateur.antenna)
  • Re: Lightning Question
    ... Having the required tower ground at this ... transmission line down from the antenna, bury the line, run it underground to the house, place a lightning arrestor and ground just outside the house, then run the transmission line up the side of the house to the operating position on the second floor. ... The tower shall also be connected to the house 'earthing' connection at the service entrance. ...
    (rec.radio.amateur.antenna)
  • Re: TV aerial gizmo
    ... We had a huge TV antenna on a 100' crank-up tower (75' of tower, ... lightning danger from noon onwatrds. ... The TV antenna tower also had lightning rods spaced at 25 feet ...
    (sci.electronics.repair)
  • Re: Grounding for Gable end bracket & mast.
    ... More than 8 feet of ground rod is of little consequence. ... However a string of ground rods tied together can be quite effective. ... The cable is clamped to each tower ... The major work for lightning rods and ground ...
    (rec.radio.amateur.antenna)
  • Re: Grounding for Gable end bracket & mast.
    ... More than 8 feet of ground rod is of little consequence. ... However a string of ground rods tied together can be quite effective. ... I'd put a circle of them around the house, ... The cable is clamped to each tower ...
    (rec.radio.amateur.antenna)