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Author Topic: Lightning Protection - Ladder Line Doublet specific  (Read 28671 times)
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W6FO
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« on: July 01, 2005, 01:54:56 PM »

Pardon my ignorance with this post but I've been off the air for the past 12 years and in the process of finally getting back on the air.

So yesterday (finally), I armed myself with a wrist rocket and, on the fifth attempt, got some line over the highest branch on the property and hoisted the center of my newly constructed doublet proudly in the air.

125' overall length center fed with roughly 150' of wide spaced homemade ladder line.  It is configured in an inverted vee configuration, apex up around 90' and ends spread out as wide as the lot would allow.  One end is ~12' off the ground but the other end is only ~7 feet off the ground.  She runs almost exactly due North to South.  The antenna measures out to right around 600 ohms.

I still have some finish work to do such as running the ladder line in the house and stuff before getting it on the air.    Antenna will be matched to the rig via an old skewl Dentron 1KW "tuner" that I scored for a good price (until I can build my own).

However, now that I have ~300' of wire in the air I got to thinking about lightning protection.  We get alot of thunderstorms here in Northern GA according to my neighbors.  What's the best thing to do in this situation?

Thanks

JT - W6FO
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« Reply #1 on: July 01, 2005, 02:44:12 PM »

Not to get offa the subject but your numbers are impossible.
Just trying to figure if your included angle is 90 degrees or more.
The center simply cannot be at 90 feet given the lengths and end heights quoted.
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W6FO
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« Reply #2 on: July 01, 2005, 02:52:29 PM »

Quote from: Dave Calhoun W2APE
Not to get offa the subject but your numbers are impossible.
Just trying to figure if your included angle is 90 degrees or more.
The center simply cannot be at 90 feet given the lengths and end heights quoted.

Well, we are splitting hairs now aren't we.  I have no clue what the exact heights and angles are.  That's why I used the term "roughly" and used the ~ symbol which also means "roughly".

I got it as high as possible and tried to spread out the legs as wide as possible.  It looks high, heh.   Just trying to do the best I can with the little I have.  At least I live on top of a nice hill with clear views around me.

So sorry to offend you.

JT - W6FO
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« Reply #3 on: July 01, 2005, 03:16:00 PM »

Who said anything about being offended. Lighten up a little. I only wanted to see if the included angle was too small.
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Mike/W8BAC
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« Reply #4 on: July 01, 2005, 04:14:23 PM »

Hi JT,

Welcome back. Your on the right track to be looking at lightening protection before you run the line in.

I use a doublet antenna similar to yours. Mine was store bought from W7FG. These are nicely made and it's been up a year now with no problems. Lightening protection has been another story.

I looked for the best I could find and the only manufactured item I could find at the time was the ICE Products Inc. suppressor sold by Array Solutions. The third item down on this page
http://www.arraysolutions.com/Products/ice/impulse1.html#2

I used the 309H which was supposed to be rated at 4KW. Not even close! At 1.5KW PEP the static suppressors smoked twice.

Inside the 309H you have a gas tube on each side and a wimpy static suppressor inductor wound on a doughnut core. The suppressors burned right away and ICE had no idea what to do.

I contacted WX0B at array solutions and he came up with a solution that worked. AS makes a beefy static suppressor inductor which I mounted outboard of the gas tube box and the system works fine now. W9AD and others use them as well.

I'm drawn to the old fashioned spark plug method and many others think it will work fine as well. Have a look and good luck. Add a pair of static suppressors to a pair of good old Champions and I think you have a working setup.

http://members.aol.com/wj5mh/notebookind1.html

Mike
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« Reply #5 on: July 01, 2005, 04:21:06 PM »

Here is a look at the static suppression inductors I use.

http://www.arraysolutions.com/Products/staticsurgecoils.htm

Mike
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« Reply #6 on: July 04, 2005, 08:33:09 PM »

Look at some old handbooks that show how to build a spark gap protector. I throw a pipe over my feed line so it sits on the ground when a storm is coming. My antenna tuner has a center tap ground so it is always at dc ground .  gfz
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W1GFH
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« Reply #7 on: July 04, 2005, 10:52:07 PM »

Quote


He's running RADIO SHACK 300 OHM TV TWINLEAD. I like that  Smiley
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« Reply #8 on: July 05, 2005, 11:22:18 AM »

Hi,
I am from the "scared school" so I throw the big switch that connects my ladderline fed doublet to GROUND and disconnects it from even going into my shack.
This is a big switch! Has inch wide copper blades about 1/8 inch thick. Very strapping but also probably low impedance to the signal and capable of shunting a large hunk of lightning current to ground. The ground is a large five foot diameter of 3/8 inch copper pipe burried about 4 or 5 feet under ground. The pipe also have copper wires coming off the burried pipe. The 3/8 inch pipe goes right up to the switch. Since the picture was taken I replace the small copper wire connecting to the copper pipe with heavier braid.


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Todd, KA1KAQ
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« Reply #9 on: July 05, 2005, 01:24:17 PM »

Along the lines of the 'spark plug' approach is the old standby 'horn' spark gap. Easy to make and adjust, works well. Depending where it's located, you might want to consider something to protect it from dust/dirt/crud accumulation, though. I like the Q setup, FrankenSwitch. Cheesy

Mike, that is an excellent site for the AS stuff. Thanks for posting it. Looks like I won't be moving as soon as I thought, so back to investigating a useable antenna system at the current location. This stuff will come in handy.
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« Reply #10 on: July 05, 2005, 04:00:50 PM »

Mike BAC those inductors are useless for lightning. They are only useful for bleeding off static. That large inductance will act like an open and full voltage will appear across them. They will flash over though but and self distruct.  We have an outside vendor come in and generate lightning for our testing. A Waveform 5 pulse is generated with a small inductance and a spark gap.  I think I saw about 6 turns of wire about 6 inches ID   this is a very nasty long pulse that makes about 600 amps in our last test.
Big oil cap stored the necessary energy.
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« Reply #11 on: July 05, 2005, 06:59:36 PM »

If you've ever seen a wire antenna blown to hell by a lighning strike, the pieces always seem to be about 3' long.  This implies that the strike has a fundamental frequency of about 100 MHz.... I concur with Frank, those inductors are worthless in a strike (but are usefull for draining static).

73 John
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« Reply #12 on: July 06, 2005, 11:39:45 AM »

Todd,

I'm not familiar with the "horn" spark gap. Maybe you have a link. Keeping the spark plug gap clean is also an issue worth considering. I think I would consider mounting the plugs on a sealed steel box and mount the box on a ground rod. Somebody sells a pair of plugs mounted on a copper strip that clamps to a ground rod. I saw that link here I think. If any readers have that link please post it. An unfortunate spider climbing across the gap during a transmission could cause a trip. If you really want to get exotic about it, purge the air out of the steel box and pressurize with argon or some other inert gas.

I used Poly Phaser "Gas Tube" devices for coaxial feed lines for years. I never looked inside, I trusted the engineering and the volumes of published research Poly Phaser produced. It wasn't until I opened the failed Ice Products device that I realized what a "Gas Tube" was. It's a simple spark gap inside a glass tube. I have to assume, because of the name, the tube is filled with some sort of inert gas. That's an assumption judged by the tubes size and the close gap. I dug out an old Poly Phaser and it uses the same thing.

For 50 ohm coaxial feed lines the Poly Phaser engineers did a fine job. Using a TDR the Poly Phaser shows a minor blip in feed line impedance. Compared to a PL259,  the suppressor is almost invisible. Doing a better job or home brewing a more effective coaxial suppressor would be difficult. Balanced feed systems are much easier to work with in my opinion.

Frank and John

I never heard of, or read about, using static bleed chokes until the ICE suppressor failed. I contacted the Ice products distributor (WX0B John Terleski) the first time and he put me in touch with the manufacturer. The second failure got his attention and we talked about it. John explained to me the bleed chokes where used to neutralize static electricity on wire arrays. Thinking back, I used to marvel at the tiny lightning discharges I would see from my multi band fan dipole system when the Santa Ana winds blew in late summer. That static rendered receivers useless. John advised removing the factory bleeders and replacing them with his chokes. I thought about doing away with them altogether until John made the reason for the chokes clear.

Your right, to a point. The bleeders will not protect the station from a lightning strike. Nothing will eliminate the possibility of damage from a direct, or indirect, strike. The objective is to minimize the possibility of inviting the energy into the shack.

My understanding of the elements of a lightning strike places the earths potential discharge at the point of the strike close to the energy potential in the clouds. A tree, a rock, a house or anything above ground level will conduct earths potential. My adopted theory states that a properly grounded tower, mast or lightning rod for that matter isn't just a good conductor to ground for lightning but actually a vent to the atmosphere for the stored potential in the earth around it.

This theory contends that the old lightning rod on the barn was the right thing to do for the wrong reason. The rod helped dissipate the earths potential. If that balance was not met at the moment of the strike the rod was hit and not the barn. This theory also holds that strikes in that barns area would be far less likely due to the high level dissipation.

Back to the bleeder chokes. It follows that if your wire array is at ground potential it is acting as a vent. Same for the tower and mast. Static electricity generated by wind or weather on a wire array may or may not have an influence on possible lightning strikes. All I know is I have no static generated by my wires and I sleep better thinking I did the best I could. It's always in the back of my mind during a storm. The possibility of a strike between 18 and 120 thousand Amps is just as likely as before this installation. Hopefully it will stay outside.

I'll be interested in hearing your comments.

Mike
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« Reply #13 on: July 06, 2005, 01:18:04 PM »

"This theory contends that the old lightning rod on the barn was
the right thing to do for the wrong reason. "


Yep, agreed!

Here's some actual experience:  

I would say that neighbors should be happy that a ham's tower
is protecting their neighborhood. And it's not by attracting strikes
away from their houses, but instead, bleeding off the charge for
the area. I have read that a tall tower will neutralize an area of
at LEAST 1/2 mile radius.... but have no scientific data to prove
this.

Before I put up towers here, I would get many, many strikes
during summer storms in the immediate area. You could count
the seconds and know they were real close, and even see
damaged trees in the woods. And, I had my share of ruined
computer cards, telephones, etc.

But now, if you were to go to the next set of hills and look at the
site here, you would see a hill top with 190' towers sticking up
high above the hill top tree line- in the clear. Common sense would
say they should be hammered all the time. But guess what? I
can't remember when these towers were hit last! It appears
they bleed the charge off and protect the area. I still hear smaller
trees getting hit within 1/2 mile or so, but not the towers. I find
this interesting.  

They are all well grounded with 15 miles! of 160M ground radial
system tied in underground. All towers are tied together underground.

So, here's an actual experience supporting the idea that a lightning
rod is for bleeding and neutralizing - and if hit, well, it will also form
a Faraday cage around the building as a bonus and pass high current
for an instant.

I look at it like one of those dragging leather straps you see under
cars sometimes. The car is kept at the same potential as the road
and the charge built up from the rubber tires spinning on the road is
bled off.

So, your ho doesn't get belted when she steps out of your ride with
her 9" spike heels.  

73,
T
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« Reply #14 on: July 06, 2005, 02:24:38 PM »

My term for this Tom is "PREFERENCE"

The current prefers to take the lowest Z path.

JN there are a number of different lightning test pulses the worst being waveform 5 if I remember. 6 US rise time 70 US fall time.
The others are shorter period. Pick you threat level which is all over the map depending on location and inside or outside.

I will share the 3 foot observation with our world known expert and see whet he says.
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« Reply #15 on: July 07, 2005, 03:15:19 PM »

I remember reading about a tower draining off the charge before it reach the flashover voltage and the article I remember reading years ago called it the cone of protection. it was formed by a 45 degree angle out from the top of the tower to the ground. It also said that a porcupine type thing at the top of the tower worked best at bleeding it off. Ofcourse the quills were made of metal. A real porcupine was a bitch getting it to sit still at the top of my tower.

Also Mike, w8bac, asked me to post a picture of his protection system here so what you see below belongs to Mike.

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K1JJ
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« Reply #16 on: July 07, 2005, 03:37:19 PM »

Hmmm..

Is that aluminum siding? If so, kinda close - feedline balance
problem. If vinyl, how about insulation metal foil underneath and
house wiring, etc?.

That control wire is also very close to the feedline.

I would mount the feedline at LEAST 6" away from the house
and control line/box.  Go in and out of  the arc box at right angles
for minimum interaction to the feedline. The coils themselves
appear to be coupling big-time to the house.

Or, better yet, mount everything in a non-metalic box on
stand-offs 6" off the wall.  Run the ground strap and control
cable in from behind at right angles with the open wire "seeing"
as little metal as possible.

It probably is "OK" as is, but little things all add up in the
whole installation.  Save a db here, a db there - eventually adds
up to a shushi dinner and a night with the best ho in town.

T
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« Reply #17 on: July 09, 2005, 07:13:25 AM »

Found in GE Ham News Volume 5 No. 5 September-October 1950. An article about ladder line lighting protection by VE2ABT.

http://home.comcast.net/~gerboid/lighting.gif
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« Reply #18 on: July 12, 2005, 06:03:30 PM »

Thanks Bob for posting the picture of my lightning arrestor setup. Maybe I'll figure that out soon and not have to take a half day doing it.

Tom, I read your posting a few days ago but have been busy. Yup, that is lunarmin siding. The feed line passes 6 inches from it for some 18 feet. Unfortunately, that was the best I could do. I am really lucky in that I don't think I am loosing much of my received signal. I will do some tests before winter. I don't have any coupling issues with house AC wiring or the alarm installation.

I have a plastic outdoor box that will fit the setup and plan to install it in the fall. I'll take your advice and make right angled connections as well. That "control wire" is actually a 1/4" ground wire from the gas tube box to the ground rod array.THANKS for the help and advice Tom.

JT, W6FO, I hope some of this helped you with your installation. Best Regards

Mike
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« Reply #19 on: July 12, 2005, 07:54:23 PM »

Hi Mike,

Sounds good, OM.

Well, you won't actually be "losing" signal, like in IR losses,
but a feedline inbalance would cause your pattern to be distorted
from a standard figure 8 or whatever it should be. Feedline radiation
can do this. In its worst case you might see big nulls of 10-20db in
areas that were previously filled in. This might result in a little gain
in other directions, but too random to think about.

As for 6" away from the siding... well, it depends upon the
spacing of your feedline leads apart from themselves. The
closer the better for less outside interaction. Some say 2X  
the feedline spacing is good enough, so that a 4" spaced
openwire needs 8" min away, etc.

But, all it takes is one near pass to an object to cause
inbalance. I think the box junction in the picture with the
coils looks like it is mounted right on the siding.   Even
though the rest of the run is 6" away, that mistake can
negate your hard work.

Again, this is nit picking and probably doesn't  amount to a hill
of beans, but since you have a choice and can do something,
it's worth getting it perfect for peace of mind...  Cheesy

73,
Tom, K1JJ
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« Reply #20 on: July 12, 2005, 08:19:20 PM »

I have to ask you a question here Tom. I came into a box full of ceramic squares last weekend.

The squares are meant for copper clad wire and space the wire maybe 1 1/2' apart but interesting enough at each spacer it is required a reversal ( the wires are bent and make a 180 in feed line impedance. What do I have? Thanks in advance.
Mike
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« Reply #21 on: July 12, 2005, 08:37:50 PM »

Mike,

Well, could be a few things...

Might be spacers for a wire feedline log periodic which needs 180
degree phase shift at each element.   Or maybe for some other kind
of driven array.

But, there may be a more mundane answer for their use in the
real whirl. Maybe some of the guys here recognize them.

73,
T
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« Reply #22 on: July 13, 2005, 01:12:26 AM »

Quote from: Mike/W8BAC
I have to ask you a question here Tom. I came into a box full of ceramic squares last weekend.
The squares are meant for copper clad wire and space the wire maybe 1 1/2' apart but interesting enough at each spacer it is required a reversal ( the wires are bent and make a 180 in feed line impedance. What do I have? Thanks in advance.  Mike

They sound like transposition spacers for long runs of open-wire-line.  When running a long run of balanced line, you need to "transpose" the wire every so often to counteract imbalances, and any crosstalk from adjacent feeders.  This is particularly the case for the old 600 ohm open-wire telephone lines.   RF transmission lines are less subject to crosstalk of course, but imbalances may still occur.
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VA3ES - Piss-Weak Ed
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« Reply #23 on: July 13, 2005, 01:22:09 AM »

This is all very interesting, particularly because I'm just now finishing up my antenna system.  It should be completed in about 3 weeks.  It'll consist of a tower at 60' with a balanced line fed doublet at the top.  It'll also sport a tri-bander (a TH3),  a six-meter yagi, and a 2M Ringo Ranger at the tippy top.  Just below the tri-bander will be an asortment of verticals on outriggers for 6M, 220 Mhz, 440 Mhz, and the air-band.  My chimney will sport the 10M  5/8ths.

Right now, I'm just getting the shack fixed up. That will take about three weeks or so.  I expect to be back on the air end of August.

OK -  so here's my question:
Can we get a synopsis of this thread?  Maybe of listing of parts and suppliers for a suitable balanced line lightning arrestor?  What is the consensus on what system is the best?
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« Reply #24 on: July 13, 2005, 01:31:28 AM »

Quote from: VA3ES - Piss-Weak Ed
They sound like transposition spacers for long runs of open-wire-line.  When running a long run of balanced line, you need to "transpose" the wire every so often to counteract imbalances, and any crosstalk from adjacent feeders.  This is particularly the case for the old 600 ohm open-wire telephone lines.   RF transmission lines are less subject to crosstalk of course, but imbalances may still occur.


Yep, now that sounds like a logical answer!  Seems I've heard Don or someone else mention this main use before somewhere, too.

Thanks, Ed.

T
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