I agree with Tom and Bob that the big, heavy choke is not needed. Even it
offers too much inductance to be an effective lightning path.
A spark gap is the thing to use across the choke or shorted 90 degree
feedline. It should have a weather cover and be set close but not too
close. See ROSS
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.
If you use an automotive spark plug make sure its not the resistor type.
Carl
KM1H
- Original Message -
From: DAVID CUTHBERT telegraph...@gmail.com
To: Bob Kupps n...@yahoo.com
Cc: topband topband@contesting.com
Sent: Friday, July 27, 2012 8:24 AM
Subject: Re: Topband: Fw: Choke
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
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
About 20 years ago I decided to do something about lightning protection.
My tower is 80 feet of Rohn 45G, with a 5el Telrex monoband 20 meter yagi at 82
feet.
Hygain 153BAS at 90 feet and Hygain 103BAS at 100 feet. I have a homemade
antenna
switch box near the top.
I shunt feed the tower
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
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
A low impedance tower ground is important. Google TOWER FOOTING RESISTANCE
for an IEEE ppt. on this. I would aim for a couple of ohms. That means
several long rods.
Dave WX7G
On Jul 27, 2012 9:06 AM, HAROLD SMITH JR w0ri...@sbcglobal.net wrote:
About 20 years ago I decided to do something about
Google carbon ball gap lightning.
Dave
On Jul 27, 2012 9:33 AM, Mike Waters mikew...@gmail.com 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
www.rossengineeringcorp.com/toroids_spheres_coronary_nuts.htm
Ross recommends carbon for lightning.
Dave WX7G
On Jul 27, 2012 9:33 AM, Mike Waters mikew...@gmail.com wrote:
I don't think carbon balls are suitable for lightning protection. Think of
the voltage drop that would appear across
- Original Message -
From: Mike Waters mikew...@gmail.com
To: topband topband@contesting.com
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
A low impedance tower ground is important. Google TOWER FOOTING RESISTANCE
for an IEEE ppt. on this. I would aim for a couple of ohms. That means
several long rods.
Dave WX7G
Dave,
Of course a low impedance ground is important.
I have a ground field with 6 - 10ft 3/4 inch schedule 80
www.rossengineeringcorp.com/toroids_spheres_corona_nuts.htm
On Jul 27, 2012 9:43 AM, DAVID CUTHBERT telegraph...@gmail.com 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
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
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
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
Tom is correct. very Low resistance and of some size is necessary to pass
the charge on down into the earth.
Carbon arcs used in movie projectors produced a very bright light for the
large viewing screen- heat was a bi-product.
Bright light and heat are un-wanted for lightening control.
73
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
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
That doesnt work for us that have solid rock as the tower base. My 180' has
solid granite at 8-14 below grade and the other 3 towers arent much better,
I think the deepest spot is 2' of sandy gravel.
The 80-100' pines make good lightning arresters and their roots are
horizontal. I push them
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 tony@verizon.net 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.
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
23 matches
Mail list logo
