Re: Topband: Spark gaps

[N2TK, Tony]

Hi Guy,
You got my curiosity up. So, there are 6 radials out of the 60 that I know
where they end. I dragged out the VOM and a long lead (100') to check.
Everything checked okay on those 6. No visible damage where the radials
attach to a 3/4" hard Cu tubing square that is attached to the concrete
pier. The Cu tubing is attached to each leg of the tower.

In addition from each tower leg I have solid #4 Cu going to 8' ground rods
that are 3' from the concrete.  The wire continue away from the tower in
these three directions with a ground rod each additional 16' for a total of
4 ground rods for each tower leg. One of the wires that points towards the
house continues for another 40' where it "T's" to a box mounted on the side
of my shed that houses the receive antenna stuff (3' x 3' aluminum plate,
coax switch, preamp, common-mode choke).  The ground wire continues to the
large aluminum panel just inside my basement where I have mounted lightning
protection devices for every coax and control wire plus a coax switch. From
the ground attach point of the panel I have a #4 solid wire going out
through the concrete to three 8' ground rods. Total ground rods - 22. 
My amp is mounted just above the panel and grounded directly to the panel. I
have a #4 wire going to the ground in the breaker box. 

I have my coax, control cables and ground wire continuing to the shack which
is right above the ground panel on the first floor.

All outside ground rod connections are made with Cadwelds.
All coax shields are connected to the bottom of the tower before they go
underground. Also connected the shields where the hardlines terminates on
the tower where I switch to Buryflex for the rotator loops.
Run all coax and control cable inside the Rohn 45 (don't know if that does
any good).

And I even had a witness to the strike. It seems lightning struck a tree
about 300' past my tower very shortly before the tower got hit. My neighbor
looked up to see what got hit. My tower was in line with the tree. He was
standing about 250' from the tower when it got hit. He ran inside after
that. Two close strikes was enough for him.

Maybe someday I will pay a price for not disconnecting anything. But after
doing it this way for 33 years I have suffered virtually no damage.

73,
N2TK, Tony
 
-Original Message-
From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com]
On Behalf Of Guy Olinger K2AV
Sent: Saturday, July 28, 2012 1:06 AM
To: N2TK, Tony
Cc: topband; donov...@starpower.net
Subject: Re: Topband: Spark gaps

What is the condition of your 160m radials after the lightning strike?  73,
Guy.

On Fri, Jul 27, 2012 at 7:48 PM, N2TK, Tony  wrote:

> As a side note, last night when the storm came barreling in with very 
> strong winds I was watching the tower as the elements whipped around. 
> Bang! First time I saw a direct hit on the tower. Had spots in my eyes 
> for a while.
> Tower is about 150' from the kitchen window.
>
> I had everything tuned off but I never disconnect anything.
> Was anxious when I turned on things this morning. Everything is fine 
> except the fuse blew on the Prosistel when I turned it on. Replaced 
> the fuse and everything is now fine.
> I guess my ground system is working. Couldn't find any burn marks 
> anywhere inside or at the tower. With no visual or electrical damage 
> maybe the tower has been hit before?
>
> By the way the tower is grounded and I shunt feed it for 160M.
>
> 73,
> N2TK, Tony
>
> -Original Message-
> From: topband-boun...@contesting.com [mailto:
> topband-boun...@contesting.com]
> On Behalf Of donov...@starpower.net
> Sent: Friday, July 27, 2012 10:58 AM
> To: topband
> Subject: Re: Topband: Spark gaps
>
> An air gap using one to two inch diameter balls with only a one or two 
> millimeter gap provides a nearly uniform field resulting in the 
> fastest breakdown at repeatable and fairly breakdown voltages but 
> capable of withstanding kilowatt transmitter power levels.
>
> Ordinary carbon steel balls used in architectural applications should 
> provide adequate protection if they are inspected -- and replaced if 
> necessary -- after a lightning strike.  For example, Wagner Industrial 
> sells two inch diameter threaded steel balls for $11.00 each.  There 
> may be alternative sources.
>
>
> http://www.shopwagnerb2c.com/SPHERES/SPHERES_ST?categoryId=315e03cf-4f
> 11-4ed 
> 9-8e89-9fea015509e5&filters=&sortby=1&page=1&pageSize=10&criteria=
>
> Very hard steel balls such as carbon or tungsten are ideal for 
> withstanding multiple lightning strikes without need for inspection 
> and replacement, but at higher cost.
>
> The balls should be aligned in the horizontal plane, to ensure rain, 
> do not bridge the

Topband: Spark Gaps..

[Robert Briggs]

Thank you to all the email's received re my use of trailer balls for a 
spark gap..It is a simple answer to a big problem and it works..

It pays to think outside the box at times when presented with a problem 
and be a bit innovative..

I also use a trailer ball at the bottom of the 90 foot mast and on my 
160 meter vertical antenna...Using triangular mast section I have 
tapered the three bottom sides of a triangular section and welded a 
trailer ball on the bottom ...I used a 66kv three skirted Electric 
supply insulator which has a galvanised metal plate on the top with four 
1/2 inch studs about 4 inches longI cut out a 1/2 inch metal plate 
to fit on top of the insulator mounting plate..I then used a piece of 
heavy 2 inch tube 3 inches long and welded it to my mounting plate..I 
reinforced the tubing on four sides with some 1/2 inch plateThis 
mounting socket is strongI drilled a couple of holes at the bottom 
of the tube as a water drain and also added a grease nippleI then 
bolted this assembly on to the insulator top plate...The insulator is in 
a 2 cubic meter concrete block in the ground with four copper clad earth 
rodsThe mast with the trailer ball sits into my home made socket and 
is well insulated from the ground..

So there you areAll you need to do is use the old noggin and many 
mechanical problems are easily solved...

73Bob..VK3ZL..
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark Gaps..

[ZR]

Figuring that .045" is a standard 2000V air gap for variable caps in medium 
humidity it would be a good place to start. For 1500V set at .030".

Everybody should have a set of feeler gauges(-;

A sacrificial size >100 uH choke should suffice as a static drain and be a 
visible indicator of whats happening.

Carl
KM1H


- Original Message - 
From: 
To: "160 reflector" 
Sent: Sunday, July 29, 2012 4:18 PM
Subject: Re: Topband: Spark Gaps..


> Trailer hitch balls should work fine as a lightning arrestor.  Typically a 
> trailer hitch ball has spherical sides and a flat top.  The two balls 
> should be oriented so they the spherical surfaces are side-by-side and so 
> that rain water and debris cannot bridge them. Ideally they should be 
> shielded from rain and insects.  The gap should be adjustable, and it 
> should be set to about the thickness of a credit card (1 to 2 mm).
>
> 73
> Frank
> W3LPL
>
>  Original message 
>>Date: Sun, 29 Jul 2012 11:33:07 -0600
>>From: DAVID CUTHBERT 
>>Subject: Re: Topband: Spark Gaps..
>>To: Robert Briggs 
>>Cc: topband@contesting.com
>>
>>Bob, that an excellent idea!
>>
>>Dave WX7G
>>On Jul 28, 2012 6:06 PM, "Robert Briggs"  wrote:
>>
>>>
>>> Has anyone thought about using two trailer towing balls set up for a
>>> spark gap?  I use this on a 90 foot insulated mast in a very lightning
>>> prone environmentTo date "(25)" years, with many direct hits, I have
>>> sustained no damage...Mast is located 20 feet from my lounge room..
>>>
>>> 73..Bob..VK3ZL..
>>> ___
>>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>>
>>___
>>UR RST IS ... ... ..9 QSB QSB - hw? BK
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
> -
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1424 / Virus Database: 2437/5162 - Release Date: 07/29/12
> 

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark Gaps..

[donovanf]

Trailer hitch balls should work fine as a lightning arrestor.  Typically a 
trailer hitch ball has spherical sides and a flat top.  The two balls should be 
oriented so they the spherical surfaces are side-by-side and so that rain water 
and debris cannot bridge them. Ideally they should be shielded from rain and 
insects.  The gap should be adjustable, and it should be set to about the 
thickness of a credit card (1 to 2 mm).  

73
Frank
W3LPL

 Original message 
>Date: Sun, 29 Jul 2012 11:33:07 -0600
>From: DAVID CUTHBERT   
>Subject: Re: Topband: Spark Gaps..  
>To: Robert Briggs 
>Cc: topband@contesting.com
>
>Bob, that an excellent idea!
>
>Dave WX7G
>On Jul 28, 2012 6:06 PM, "Robert Briggs"  wrote:
>
>>
>> Has anyone thought about using two trailer towing balls set up for a
>> spark gap?  I use this on a 90 foot insulated mast in a very lightning
>> prone environmentTo date "(25)" years, with many direct hits, I have
>> sustained no damage...Mast is located 20 feet from my lounge room..
>>
>> 73..Bob..VK3ZL..
>> ___
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
>___
>UR RST IS ... ... ..9 QSB QSB - hw? BK
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark Gaps..

[DAVID CUTHBERT]

Bob, that an excellent idea!

Dave WX7G
On Jul 28, 2012 6:06 PM, "Robert Briggs"  wrote:

>
> Has anyone thought about using two trailer towing balls set up for a
> spark gap?  I use this on a 90 foot insulated mast in a very lightning
> prone environmentTo date "(25)" years, with many direct hits, I have
> sustained no damage...Mast is located 20 feet from my lounge room..
>
> 73..Bob..VK3ZL..
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Gary K9GS]

Sorry...couldn't resist

http://www.youtube.com/watch?v=g23GiivXC78



On 7/27/2012 4:31 PM, kd9sv wrote:
> Silly me, and to think they were probably referring to "Carbon Steel Balls"
> not Carbon balls...de gary
>
> -Original Message-
> From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com]
> On Behalf Of donov...@starpower.net
> Sent: Friday, July 27, 2012 5:26 PM
> To: topband
> Subject: Re: Topband: Spark gaps
>
> This link shows the base of a typical AM broadcast tower, with two hard
> steel balls used as lightning protection.  At kilowatt power levels its not
> unusual to use a credit card to set the gap.
>
> http://www.thebdr.net/articles/steel/twrs/LimitingStatic.pdf
>
> 73
> Frank
> W3LPL
>
>
>
>  Original message 
>> Date: Fri, 27 Jul 2012 16:29:15 -0400
>> From: "Tom W8JI" 
>> Subject: Re: Topband: Spark gaps
>> To: "Mike Waters" , "topband" 
>>
>>> Man, I don't know, Dave. How long have they been selling those carbon
>>> balls
>>> for that purpose?
>> I've never seen a carbon ball in a lightning gap application. I'd have to
>> see a few after being in action a long time before trusting them.
>>
>> Broadcast stations use hard metallic balls, as do electrical substations
> and
>> other applications where the peak voltage is near gap voltage. Polished
>> round gaps have more consistent breakdown.
>>
>> If there is a great deal of headroom between operating and breakover
>> threshold, a pointed gap works OK.
>>
>> ___
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>

-- 


73,

Gary K9GS

Greater Milwaukee DX Association: http://www.gmdxa.org
Society of Midwest Contesters: http://www.w9smc.com
CW Ops #1032   http://www.cwops.org



___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Topband: Spark Gaps..

[Robert Briggs]

Has anyone thought about using two trailer towing balls set up for a 
spark gap?  I use this on a 90 foot insulated mast in a very lightning 
prone environmentTo date "(25)" years, with many direct hits, I have 
sustained no damage...Mast is located 20 feet from my lounge room..

73..Bob..VK3ZL..
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Gregg W6IZT]

I took a lightning strike to my shunt fed tower crank up earlier this year.
It vaporized the #8 wire that ran from the top to the bottom of the tower.
Some of the radials turned into fuses. Interestingly, not at the base of the
tower, but 50 - 60 ft from the base.

I disconnect all of the feed lines and control cables outside of the shack
when not in use. 

73
Gregg

-Original Message-
From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com]
On Behalf Of Guy Olinger K2AV
Sent: Saturday, July 28, 2012 01:06
To: N2TK, Tony
Cc: topband; donov...@starpower.net
Subject: Re: Topband: Spark gaps

What is the condition of your 160m radials after the lightning strike?  73,
Guy.

On Fri, Jul 27, 2012 at 7:48 PM, N2TK, Tony  wrote:

> As a side note, last night when the storm came barreling in with very
> strong
> winds I was watching the tower as the elements whipped around. Bang! First
> time I saw a direct hit on the tower. Had spots in my eyes for a while.
> Tower is about 150' from the kitchen window.
>
> I had everything tuned off but I never disconnect anything.
> Was anxious when I turned on things this morning. Everything is fine
except
> the fuse blew on the Prosistel when I turned it on. Replaced the fuse and
> everything is now fine.
> I guess my ground system is working. Couldn't find any burn marks anywhere
> inside or at the tower. With no visual or electrical damage maybe the
tower
> has been hit before?
>
> By the way the tower is grounded and I shunt feed it for 160M.
>
> 73,
> N2TK, Tony
>
> -Original Message-
> From: topband-boun...@contesting.com [mailto:
> topband-boun...@contesting.com]
> On Behalf Of donov...@starpower.net
> Sent: Friday, July 27, 2012 10:58 AM
> To: topband
> Subject: Re: Topband: Spark gaps
>
> An air gap using one to two inch diameter balls with only a one or two
> millimeter gap provides a nearly uniform field resulting in the fastest
> breakdown at repeatable and fairly breakdown voltages but capable of
> withstanding kilowatt transmitter power levels.
>
> Ordinary carbon steel balls used in architectural applications should
> provide adequate protection if they are inspected -- and replaced if
> necessary -- after a lightning strike.  For example, Wagner Industrial
> sells
> two inch diameter threaded steel balls for $11.00 each.  There may be
> alternative sources.
>
>
>
http://www.shopwagnerb2c.com/SPHERES/SPHERES_ST?categoryId=315e03cf-4f11-4ed
> 9-8e89-9fea015509e5&filters=&sortby=1&page=1&pageSize=10&criteria=
>
> Very hard steel balls such as carbon or tungsten are ideal for
withstanding
> multiple lightning strikes without need for inspection and replacement,
but
> at higher cost.
>
> The balls should be aligned in the horizontal plane, to ensure rain, do
not
> bridge the gap.  Preferably, the balls should be installed in a
> weather/insect/rhodent proof enclosure.
>
> 73
> Frank
> W3LPL
>
>
>  Original message 
> >Date: Fri, 27 Jul 2012 10:09:16 -0400
> >From: "Tom W8JI" 
> >Subject: Topband: Spark gaps
> >To: "topband" 
> >
> >Has anyone looked at, or looked for, cheap electric fence gaps??
> >
> >My system copper pipes near tower legs work great for me on rigid
> >towers, I can bend them so they spring away from the tower and then
> >slide an inner pipe in or out to set gap distance. I'm thinking of gaps
> for
> wire antennas.
> >
> >Maybe something is good from some other application that is a good bit
> >better than a spark plug.
> >
> >___
> >UR RST IS ... ... ..9 QSB QSB - hw? BK
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Jim WA9YSD]

Take 2 rods and grind a point on each rod. Point the points toward each other. 
There is your spark gap.

You can do the dame thing with copper flat stock used on building grounds in 
electrical valts.
 
Stay on course, fight a good fight, and keep the faith. Jim K9TF/WA9YSD
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Guy Olinger K2AV]

What is the condition of your 160m radials after the lightning strike?  73,
Guy.

On Fri, Jul 27, 2012 at 7:48 PM, N2TK, Tony  wrote:

> As a side note, last night when the storm came barreling in with very
> strong
> winds I was watching the tower as the elements whipped around. Bang! First
> time I saw a direct hit on the tower. Had spots in my eyes for a while.
> Tower is about 150' from the kitchen window.
>
> I had everything tuned off but I never disconnect anything.
> Was anxious when I turned on things this morning. Everything is fine except
> the fuse blew on the Prosistel when I turned it on. Replaced the fuse and
> everything is now fine.
> I guess my ground system is working. Couldn't find any burn marks anywhere
> inside or at the tower. With no visual or electrical damage maybe the tower
> has been hit before?
>
> By the way the tower is grounded and I shunt feed it for 160M.
>
> 73,
> N2TK, Tony
>
> -Original Message-
> From: topband-boun...@contesting.com [mailto:
> topband-boun...@contesting.com]
> On Behalf Of donov...@starpower.net
> Sent: Friday, July 27, 2012 10:58 AM
> To: topband
> Subject: Re: Topband: Spark gaps
>
> An air gap using one to two inch diameter balls with only a one or two
> millimeter gap provides a nearly uniform field resulting in the fastest
> breakdown at repeatable and fairly breakdown voltages but capable of
> withstanding kilowatt transmitter power levels.
>
> Ordinary carbon steel balls used in architectural applications should
> provide adequate protection if they are inspected -- and replaced if
> necessary -- after a lightning strike.  For example, Wagner Industrial
> sells
> two inch diameter threaded steel balls for $11.00 each.  There may be
> alternative sources.
>
>
> http://www.shopwagnerb2c.com/SPHERES/SPHERES_ST?categoryId=315e03cf-4f11-4ed
> 9-8e89-9fea015509e5&filters=&sortby=1&page=1&pageSize=10&criteria=
>
> Very hard steel balls such as carbon or tungsten are ideal for withstanding
> multiple lightning strikes without need for inspection and replacement, but
> at higher cost.
>
> The balls should be aligned in the horizontal plane, to ensure rain, do not
> bridge the gap.  Preferably, the balls should be installed in a
> weather/insect/rhodent proof enclosure.
>
> 73
> Frank
> W3LPL
>
>
>  Original message 
> >Date: Fri, 27 Jul 2012 10:09:16 -0400
> >From: "Tom W8JI" 
> >Subject: Topband: Spark gaps
> >To: "topband" 
> >
> >Has anyone looked at, or looked for, cheap electric fence gaps??
> >
> >My system copper pipes near tower legs work great for me on rigid
> >towers, I can bend them so they spring away from the tower and then
> >slide an inner pipe in or out to set gap distance. I'm thinking of gaps
> for
> wire antennas.
> >
> >Maybe something is good from some other application that is a good bit
> >better than a spark plug.
> >
> >___
> >UR RST IS ... ... ..9 QSB QSB - hw? BK
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[N2TK, Tony]

As a side note, last night when the storm came barreling in with very strong
winds I was watching the tower as the elements whipped around. Bang! First
time I saw a direct hit on the tower. Had spots in my eyes for a while.
Tower is about 150' from the kitchen window.

I had everything tuned off but I never disconnect anything.
Was anxious when I turned on things this morning. Everything is fine except
the fuse blew on the Prosistel when I turned it on. Replaced the fuse and
everything is now fine.
I guess my ground system is working. Couldn't find any burn marks anywhere
inside or at the tower. With no visual or electrical damage maybe the tower
has been hit before? 

By the way the tower is grounded and I shunt feed it for 160M.

73,
N2TK, Tony

-Original Message-
From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com]
On Behalf Of donov...@starpower.net
Sent: Friday, July 27, 2012 10:58 AM
To: topband
Subject: Re: Topband: Spark gaps

An air gap using one to two inch diameter balls with only a one or two
millimeter gap provides a nearly uniform field resulting in the fastest
breakdown at repeatable and fairly breakdown voltages but capable of
withstanding kilowatt transmitter power levels. 

Ordinary carbon steel balls used in architectural applications should
provide adequate protection if they are inspected -- and replaced if
necessary -- after a lightning strike.  For example, Wagner Industrial sells
two inch diameter threaded steel balls for $11.00 each.  There may be
alternative sources.

http://www.shopwagnerb2c.com/SPHERES/SPHERES_ST?categoryId=315e03cf-4f11-4ed
9-8e89-9fea015509e5&filters=&sortby=1&page=1&pageSize=10&criteria=

Very hard steel balls such as carbon or tungsten are ideal for withstanding
multiple lightning strikes without need for inspection and replacement, but
at higher cost.

The balls should be aligned in the horizontal plane, to ensure rain, do not
bridge the gap.  Preferably, the balls should be installed in a
weather/insect/rhodent proof enclosure. 

73
Frank
W3LPL


 Original message 
>Date: Fri, 27 Jul 2012 10:09:16 -0400
>From: "Tom W8JI" 
>Subject: Topband: Spark gaps
>To: "topband" 
>
>Has anyone looked at, or looked for, cheap electric fence gaps??
>
>My system copper pipes near tower legs work great for me on rigid 
>towers, I can bend them so they spring away from the tower and then 
>slide an inner pipe in or out to set gap distance. I'm thinking of gaps for
wire antennas.
>
>Maybe something is good from some other application that is a good bit 
>better than a spark plug.
>
>___
>UR RST IS ... ... ..9 QSB QSB - hw? BK
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[DAVID CUTHBERT]

I do make (all too frequent) mistakes so check away. Carbon is 2000 times
more resistive than copper. Being more resistive the carbon skin depth at
lightning frequencies is much deeper than copper or steel (note the steel
is magnetically saturated).

Dave
On Jul 27, 2012 3:26 PM, "Mike Waters"  wrote:

> Thanks, Dave. That's amazing, and I won't argue anymore, even though I
> didn't (and probably won't) check your figures.
>
> I would have thought that the carbon sphere would have a MUCH greater
> resistance than .003 ohms.
>
> 73, Mike
> www.w0btu.com
>
> On Fri, Jul 27, 2012 at 3:42 PM, DAVID CUTHBERT wrote:
>
>> A ... one inch sphere about 3 m ohms. ... The observe heats 43 deg C
>>
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[kd9sv]

Silly me, and to think they were probably referring to "Carbon Steel Balls"
not Carbon balls...de gary

-Original Message-
From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com]
On Behalf Of donov...@starpower.net
Sent: Friday, July 27, 2012 5:26 PM
To: topband
Subject: Re: Topband: Spark gaps

This link shows the base of a typical AM broadcast tower, with two hard
steel balls used as lightning protection.  At kilowatt power levels its not
unusual to use a credit card to set the gap.

http://www.thebdr.net/articles/steel/twrs/LimitingStatic.pdf

73
Frank
W3LPL



 Original message 
>Date: Fri, 27 Jul 2012 16:29:15 -0400
>From: "Tom W8JI"   
>Subject: Re: Topband: Spark gaps  
>To: "Mike Waters" , "topband" 
>
>> Man, I don't know, Dave. How long have they been selling those carbon 
>> balls
>> for that purpose?
>
>I've never seen a carbon ball in a lightning gap application. I'd have to 
>see a few after being in action a long time before trusting them.
>
>Broadcast stations use hard metallic balls, as do electrical substations
and 
>other applications where the peak voltage is near gap voltage. Polished 
>round gaps have more consistent breakdown.
>
>If there is a great deal of headroom between operating and breakover 
>threshold, a pointed gap works OK. 
>
>___
>UR RST IS ... ... ..9 QSB QSB - hw? BK
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Mike Waters]

Thanks, Dave. That's amazing, and I won't argue anymore, even though I
didn't (and probably won't) check your figures.

I would have thought that the carbon sphere would have a MUCH greater
resistance than .003 ohms.

73, Mike
www.w0btu.com

On Fri, Jul 27, 2012 at 3:42 PM, DAVID CUTHBERT wrote:

> A ... one inch sphere about 3 m ohms. ... The observe heats 43 deg C
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[donovanf]

This link shows the base of a typical AM broadcast tower, with two hard steel 
balls used as lightning protection.  At kilowatt power levels its not unusual 
to use a credit card to set the gap.

http://www.thebdr.net/articles/steel/twrs/LimitingStatic.pdf

73
Frank
W3LPL



 Original message 
>Date: Fri, 27 Jul 2012 16:29:15 -0400
>From: "Tom W8JI"   
>Subject: Re: Topband: Spark gaps  
>To: "Mike Waters" , "topband" 
>
>> Man, I don't know, Dave. How long have they been selling those carbon 
>> balls
>> for that purpose?
>
>I've never seen a carbon ball in a lightning gap application. I'd have to 
>see a few after being in action a long time before trusting them.
>
>Broadcast stations use hard metallic balls, as do electrical substations and 
>other applications where the peak voltage is near gap voltage. Polished 
>round gaps have more consistent breakdown.
>
>If there is a great deal of headroom between operating and breakover 
>threshold, a pointed gap works OK. 
>
>___
>UR RST IS ... ... ..9 QSB QSB - hw? BK
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[DAVID CUTHBERT]

Mike, here it is.

The resistivity of amorphous carbon is 35 u ohm meters

(That's a 1 meter cube)

A 1" cube has a resistivity of 1.4 m ohms, a one inch sphere about 3 m ohms.

100 kA for 20 us dumps 600 J into it.

The density of carbon is 2.3 g/cm cubed

The 1 inch sphere has a mass of 20 grams

The specific heat capacity of carbon is 700 J/kg k

The observe heats 43 deg C

Dave WX7G
On Jul 27, 2012 2:18 PM, "Mike Waters"  wrote:

> Man, I don't know, Dave. How long have they been selling those carbon balls
> for that purpose?
>
> I don't have the figures in front of me, but carbon has a significant
> amount of resistance. (Maybe that's the secret: the current gets limited as
> a result. :-)
>
> It would be interesting to calculate the resistance of a carbon sphere
> sometime (how big are those?). Then we could roughly estimate the voltage
> drop across it and so come up with a ballpark figure of the instantaneous
> power dissipated in those balls.
>
> At that point, someone with way too much time on their hands could estimate
> the temperature rise based on the specific heat of carbon. :-)
>
> 73, Mike
> www.w0btu.com
>
> On Fri, Jul 27, 2012 at 2:42 PM, DAVID CUTHBERT  >wrote:
>
> >   www.rossengineeringcorp.com/toroids_spheres_corona_nuts.htm
> > On Jul 27, 2012 9:43 AM, "DAVID CUTHBERT" 
> wrote:
> >
> >>  
> >>
> >> Ross recommends carbon for lightning.
> >> On Jul 27, 2012 9:33 AM, "Mike Waters"  wrote:
> >>
> >>> I don't think carbon balls are suitable for lightning protection. Think
> >>> of
> >>> the voltage drop that would appear across each ball during a direct
> hit.
> >>> I
> >>> think they would vaporize.
> >>>
> >>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Tom W8JI]

> Man, I don't know, Dave. How long have they been selling those carbon 
> balls
> for that purpose?

I've never seen a carbon ball in a lightning gap application. I'd have to 
see a few after being in action a long time before trusting them.

Broadcast stations use hard metallic balls, as do electrical substations and 
other applications where the peak voltage is near gap voltage. Polished 
round gaps have more consistent breakdown.

If there is a great deal of headroom between operating and breakover 
threshold, a pointed gap works OK. 

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Mike Waters]

Man, I don't know, Dave. How long have they been selling those carbon balls
for that purpose?

I don't have the figures in front of me, but carbon has a significant
amount of resistance. (Maybe that's the secret: the current gets limited as
a result. :-)

It would be interesting to calculate the resistance of a carbon sphere
sometime (how big are those?). Then we could roughly estimate the voltage
drop across it and so come up with a ballpark figure of the instantaneous
power dissipated in those balls.

At that point, someone with way too much time on their hands could estimate
the temperature rise based on the specific heat of carbon. :-)

73, Mike
www.w0btu.com

On Fri, Jul 27, 2012 at 2:42 PM, DAVID CUTHBERT wrote:

>   www.rossengineeringcorp.com/toroids_spheres_corona_nuts.htm
> On Jul 27, 2012 9:43 AM, "DAVID CUTHBERT"  wrote:
>
>>  
>>
>> Ross recommends carbon for lightning.
>> On Jul 27, 2012 9:33 AM, "Mike Waters"  wrote:
>>
>>> I don't think carbon balls are suitable for lightning protection. Think
>>> of
>>> the voltage drop that would appear across each ball during a direct hit.
>>> I
>>> think they would vaporize.
>>>
>>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[DAVID CUTHBERT]

  www.rossengineeringcorp.com/toroids_spheres_corona_nuts.htm
On Jul 27, 2012 9:43 AM, "DAVID CUTHBERT"  wrote:

> www.rossengineeringcorp.com/toroids_spheres_coronary_nuts.htm
>
> Ross recommends carbon for lightning.
>
> Dave WX7G
> On Jul 27, 2012 9:33 AM, "Mike Waters"  wrote:
>
>> I don't think carbon balls are suitable for lightning protection. Think of
>> the voltage drop that would appear across each ball during a direct hit. I
>> think they would vaporize.
>>
>> At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not
>> one
>> of the applications mentioned for their carbon balls.
>>
>> 73, Mike
>> www.w0btu.com
>>
>> On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT > >wrote:
>>
>> > Note that Ross Engineering uses carbon balls on their spark gaps.
>> >
>> ___
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Tom W8JI]

- Original Message - 
From: "Mike Waters" 
To: "topband" 
Sent: Friday, July 27, 2012 11:33 AM
Subject: Re: Topband: Spark gaps


>I don't think carbon balls are suitable for lightning protection.


I agree. The last thing we want is high surface resistivity, unless we want 
something to heat and vaporize. With high core resistivity, we could make it 
explode. :-) 

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[DAVID CUTHBERT]

www.rossengineeringcorp.com/toroids_spheres_coronary_nuts.htm

Ross recommends carbon for lightning.

Dave WX7G
On Jul 27, 2012 9:33 AM, "Mike Waters"  wrote:

> I don't think carbon balls are suitable for lightning protection. Think of
> the voltage drop that would appear across each ball during a direct hit. I
> think they would vaporize.
>
> At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not
> one
> of the applications mentioned for their carbon balls.
>
> 73, Mike
> www.w0btu.com
>
> On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT  >wrote:
>
> > Note that Ross Engineering uses carbon balls on their spark gaps.
> >
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[DAVID CUTHBERT]

Google "carbon ball gap lightning."

Dave
On Jul 27, 2012 9:33 AM, "Mike Waters"  wrote:

> I don't think carbon balls are suitable for lightning protection. Think of
> the voltage drop that would appear across each ball during a direct hit. I
> think they would vaporize.
>
> At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not
> one
> of the applications mentioned for their carbon balls.
>
> 73, Mike
> www.w0btu.com
>
> On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT  >wrote:
>
> > Note that Ross Engineering uses carbon balls on their spark gaps.
> >
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Mike Waters]

I don't think carbon balls are suitable for lightning protection. Think of
the voltage drop that would appear across each ball during a direct hit. I
think they would vaporize.

At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not one
of the applications mentioned for their carbon balls.

73, Mike
www.w0btu.com

On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT wrote:

> Note that Ross Engineering uses carbon balls on their spark gaps.
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[Bill Wichers]

You can get chrome steel balls too and they are *very* hard (usually
used for ball bearings). You have to drill them with solid carbide
drills. I don't think it would be possible to thread the holes using
normal taps though.

  -Bill

[snip]
> Very hard steel balls such as carbon or tungsten are ideal for
> withstanding multiple lightning strikes without need for inspection
and
> replacement, but at higher cost.
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[donovanf]

An air gap using one to two inch diameter balls with only a one or two 
millimeter gap provides a nearly uniform field resulting in the fastest 
breakdown at repeatable and fairly breakdown voltages but capable of 
withstanding kilowatt transmitter power levels. 

Ordinary carbon steel balls used in architectural applications should provide 
adequate protection if they are inspected -- and replaced if necessary -- after 
a lightning strike.  For example, Wagner Industrial sells two inch diameter 
threaded steel balls for $11.00 each.  There may be alternative sources.

http://www.shopwagnerb2c.com/SPHERES/SPHERES_ST?categoryId=315e03cf-4f11-4ed9-8e89-9fea015509e5&filters=&sortby=1&page=1&pageSize=10&criteria=

Very hard steel balls such as carbon or tungsten are ideal for withstanding 
multiple lightning strikes without need for inspection and replacement, but at 
higher cost.

The balls should be aligned in the horizontal plane, to ensure rain, do not 
bridge the gap.  Preferably, the balls should be installed in a 
weather/insect/rhodent proof enclosure. 

73
Frank
W3LPL


 Original message 
>Date: Fri, 27 Jul 2012 10:09:16 -0400
>From: "Tom W8JI"   
>Subject: Topband: Spark gaps  
>To: "topband" 
>
>Has anyone looked at, or looked for, cheap electric fence gaps??
>
>My system copper pipes near tower legs work great for me on rigid towers, I 
>can bend them so they spring away from the tower and then slide an inner 
>pipe in or out to set gap distance. I'm thinking of gaps for wire antennas.
>
>Maybe something is good from some other application that is a good bit 
>better than a spark plug. 
>
>___
>UR RST IS ... ... ..9 QSB QSB - hw? BK
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Spark gaps

[DAVID CUTHBERT]

Yes a direct hit should vaporize a spark plug. For a 100 kA hit two 1"
diameter rounded steel balls may survive.

Note that Ross Engineering uses carbon balls on their spark gaps.

At 50 kA/us every inch of wire will have a voltage drop of 500 to 1000
volts, so very short wires are in order. Wide copper straps having a
length-to-width ratio of 5:1 are good.

Dave WX7G
On Jul 27, 2012 8:09 AM, "Tom W8JI"  wrote:

> Has anyone looked at, or looked for, cheap electric fence gaps??
>
> My system copper pipes near tower legs work great for me on rigid towers, I
> can bend them so they spring away from the tower and then slide an inner
> pipe in or out to set gap distance. I'm thinking of gaps for wire antennas.
>
> Maybe something is good from some other application that is a good bit
> better than a spark plug.
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Topband: Spark gaps

[Tom W8JI]

Has anyone looked at, or looked for, cheap electric fence gaps??

My system copper pipes near tower legs work great for me on rigid towers, I 
can bend them so they spring away from the tower and then slide an inner 
pipe in or out to set gap distance. I'm thinking of gaps for wire antennas.

Maybe something is good from some other application that is a good bit 
better than a spark plug. 

___
UR RST IS ... ... ..9 QSB QSB - hw? BK