SSB Antenna connection

[Jack Painter]

Sorry Jack but you are wrong. It has nothing to do with microwave
frequencies. A wave guide beyond cutoff is the mode that the tube is
operating in and it simply tells you that the frequency is too low for
the given size tube to propagate through. The energy inside the tube
gets shorted out. Many 2-30 mhz signal generators use that type
attenuator.

Hi Gary, the difference that is relevant, I believe, is a waveguide for
microwave broadcast through the inside space of the guide, and there is
minmal current intentionally allowed on the waveguide. As I did explain,
skin effect must be avoided in microwave and it is due to the frequencies,
however it may be exploited in HF conductors which can eliminate wasted
center-core weight and cost. This is because of the drastically different
behavior of microwave from HF. And velocities inside a waveguide are much
faster than HF on a conductor. The attenuator you are describing allows
skin effect (it cannot avoid it either) but the true waveguide avoids it,
with the microwave reflecting off the walls of the guide. Hams can use a
tubing-shield to fox hunt in a building, but it is a stretch of the phrase
to call hiding a hh in the tube a wave guide beyond cutoff.

gage.

It has everything to do with it. Skin effect is ever present in all
conductors at ALL frequencies. Note my reference to 60 hz power
transmission where it is also important.

Sorry Gary, that is not accurate. There is none in DC and very little until
VHF. It has no measureable difference to us for purposes of our discussion
between copper strap and copper tube at HF. Lightning would discover a
different impedance and pick the lower one, whichever that was. You or I or
any of our 150w or 1,000w radio equpment cannot tell the difference. By the
same math, 60hz has no skin effect for home wiring. Long, high power
transmission lines do not enter into a discussion about home wiring, and
neither should mircrowave or skin effect of copper tubing (which there is
none) enter into discussion about an RF ground on a sailboat or other low
power station. It is irrelevant between any copper conductors of similar
surface area and cross section.

While skin effect is a gradient and not an absolute barrier, there is
current that flows at all levels in a conductor. Even on the inner
surface of your copper tube. But the amount of current there is so
small that it is immeasurable. It decreases exponentially.

One skin depth is defined as the depth at which the current has
dropped to about .37 times the current at the surface. (If you notice,
this is the same decay rate that a capacitor has when it charges or
discharges.) When you go that same distance (deeper) again the
remaining current will again drop to .37 times the current that it was
at the first skin depth.

So you can see that the current never reaches zero as you go deeper
but it only takes a few skin depths to decrease the current to a very
small value which is insignificant.

.0058" is the skin depth in copper at 200 khz. Skin depth decreases by
10 for each 100 times increase in frequency. So at 20 mhz the skin
depth would decrease by 100 from that. It gets pretty thin!

Please check your premises. There is no standard depth for any frequency,
rather it varies drastically from one ohmic value of a given material
(conductor) to another. Since we're talking about copper, it's skin depth is
considered fully cross sectional at below 100 megahertz and a thickness of
..0025". At 15mhz on tubing or strap, it is using a full cross section to
carry power, not stray eddy currents. Design of course uses no more than the
proper combination of surface area and cross section to handle the required
frequency and power. Paper thin copper tape has limited usefulness to us,
because it can handle so little current, no matter how great it's surface
area. Copper tape amounts to roughly 1/3 the possible skin depth for copper
at HF, so it is just a cheap and poor alternative for copper strap. Thicker
than that, and we would be wasting center area that would carry little
current. Nobody said coax was the best conductor, it's just the most
economical. ;-)

Cheers,

Jack

 

[Jack Painter]

Actually, in a plastic boat, the radiation from the ground strap is useful
radiation. You've just moved the FEEDPOINT up the radiating element above
the sea. My feedpoint is about 4.8' above ground on Lionheart. It's
signal strength 5, readability 8 in Moscow, Belarus, UAE, Japan, Brazil,
most of Western Europe on 40 meters and 20 meters. Works pretty good!

Larry, we've probably had the details of this antenna system in pieces
across various posts, but would you mind putting in one place here? Sounds
like an intersting and well thought out setup.

Thanks,

Jack

 

[Jack Painter]

This topic is interesting. I've seen a lot of opinions expressed,
some pretty startingly. Can you posters to this thread provide
some math and/or references?
Thanks,
Norm B

Norm, because acsii graphics for the formulas you requested do not display
well in newsgroups, here is a collection of the formulas and text from
various websites regarding skin effect:

http://members.cox.net/pc-usa/station/skineffect.htm

Best regards,
Jack

 

[Jack Painter]

Wrong Jack. Electromagnetic waves in a waveguide are only possible when
voltages and currents are present. The maximum voltage is between the two
larger sides while currents flow from one side to the other. The entire
field is contained inside the waveguide and therefore the inside surface
must have a low resistance and is silver plated to achieve this. You can
read this in any textbook on microwave transmission.

Hi Meindert, how is that skin effect when, as you said, the currents must
flow from one side to the other? Skin effect would hold currents _on_ the
surface, slow them down, and reduce the reflection that is required for
propagation through the guide.

Why do you think a microwave reflects on the wall of the waveguide? Because
current flows on the inside wall, which has to have the lowest resistance
possible. It is all skin effect what makes a waveguide tick!

That sounds like a contradiction (current flows from one side to the other,
and current flows on the inside wall, [the latter of which would be skin
effect] ), can you explain please?

Thanks,

Jack

 

[Gary Schafer]

Hi Gary, the difference that is relevant, I believe, is a waveguide for
microwave broadcast through the inside space of the guide, and there is
minmal current intentionally allowed on the waveguide. As I did explain,
skin effect must be avoided in microwave and it is due to the frequencies,
however it may be exploited in HF conductors which can eliminate wasted
center-core weight and cost. This is because of the drastically different
behavior of microwave from HF. And velocities inside a waveguide are much
faster than HF on a conductor. The attenuator you are describing allows
skin effect (it cannot avoid it either) but the true waveguide avoids it,
with the microwave reflecting off the walls of the guide. Hams can use a
tubing-shield to fox hunt in a building, but it is a stretch of the phrase
to call hiding a hh in the tube a wave guide beyond cutoff.

Please check your premises. There is no standard depth for any frequency,
rather it varies drastically from one ohmic value of a given material
(conductor) to another.

Jack, what velocities are you talking about that are different at
microwaves? The frequency has nothing to do with how fast energy
propagates in a transmission line or anywhere else, regardless of what
you may think you read somewhere.

Electron movement may slow as frequency increases because of the
magnetic forces developed in the conductor but that does not slow the
energy transfer. It only forces the electrons to flow closer to the
surface of the conductor. (skin effect) The electrons deeper in the
conductor are stopped from moving by the counter magnetic fields
developed in the conductor. That is what you are reading about that is
moving slower.

The only reason I even mention wave guides here is that I mentioned
"WAVE GUIDE BEYOND CUTOFF" that is the proper electrical term to
describe why RF does not flow on the inside of a copper tube even if
the end of the tube is open and connected to the outside of the tube.

When the frequency is too low for the diameter of the tube to function
as a wave guide then it is said to be acting as a wave guide that is
beyond the cutoff frequency. Meaning RF will not propagate through it.
And propagation in the wave guide mode is the ONLY way that current
will flow on the inside of a copper tube.

Coax cable must have a center conductor in it in order for current to
flow on the inside of a coax cable. Otherwise it will perform just
like the copper tube.

By the way there are very high currents that flow on the inside walls
of a wave guide. That is why they are usually silver plated inside. It
is a transmission line.

Jack, I don't know what you have been reading in regards to skin
effect but it is very real and present. Any time the frequency is
above DC it is present. In some cases at low frequencies it can be
ignored because it is insignificant but at radio frequencies it does
come into play. And also as I mentioned in power transmission it is a
factor to be considered even though the frequency is only 60 hz. In
home wiring it is not a factor to be concerned with as the conductors
are too small but in large transmission lines it is of concern.

At HF frequencies skin effect is enough that the RF does not penetrate
even the thinnest cable shield of a coax cable. Even typical "hard
line" coax has a thinner shield than typical copper pipe that you are
saying "conducts clear through". Why do you think then that there can
be no RF energy on the outside of a coax cable??

I don't know what you mean "there is no standard depth for any
frequency"? It is well known.

At 60 hz the skin depth is around 1/3 of an inch. Very significant in
a power transmission cable. Or a lightning ground cable..
Look up any large power cable ratings and you will usually find a DC
resistance specified and an AC resistance also specified. The AC
resistance is due to skin effect.

Here are some figures on skin depth for copper: Skin depth (in mils) =
2.602/(sq. root of frequency in Mhz). At 1.8 Mhz it's 1.94 mils or
..00194 inches, just under 2 thousandths. It decreases as the inverse
square root of frequency so at twice the frequency it will be .707
times as deep, and half as deep at 4 times the frequency. At 29.7 Mhz
it's about half a thousandth. At 4 or 5 skin depths any additional
thickness ceases to have additional value.

Now how can you argue with that! :>)

Regards
Gary

 

[Jack Painter]

Jack, I don't know what you have been reading in regards to skin
effect but it is very real and present.

Hi Gary, when a poster asked for the formulas for this discussion, I could
not display them in the newsgroup (ascii) so I pasted several of them on a
website.....

http://members.cox.net/pc-usa/station/skineffect.htm

I don't know what you mean "there is no standard depth for any
frequency"? It is well known.

The resistance of a particular conductor, not just it's material, must be
known to calculate skin depth. Averaging it with constants will produce the
wide variety of depths that are seen in different formulas and tables.

At 60 hz the skin depth is around 1/3 of an inch. Very significant in
a power transmission cable. Or a lightning ground cable..
Look up any large power cable ratings and you will usually find a DC
resistance specified and an AC resistance also specified. The AC
resistance is due to skin effect.

Yes I agreed with you it is relevant only at very high power or long lengths
when inductive reactance becomes as important as DC resistance.

Here are some figures on skin depth for copper: Skin depth (in mils) =
2.602/(sq. root of frequency in Mhz). At 1.8 Mhz it's 1.94 mils or
.00194 inches, just under 2 thousandths. It decreases as the inverse
square root of frequency so at twice the frequency it will be .707
times as deep, and half as deep at 4 times the frequency. At 29.7 Mhz
it's about half a thousandth. At 4 or 5 skin depths any additional
thickness ceases to have additional value.

Gary, the problem with using those constants is, again, it will allow you to
reduce the skin depth to nearly nothing, when in fact below a certain cross
section at HF frequencies, formula predictions for skin depth cease to be
relevant. The current, assumed to be constant, cannot continue to use less
and less cross section until it has nothing to work with. The formulas are
an approximation that allows designers to consider the resistance casued by
skin effect and use an appropriately sized conductor. For instance, I could
not use 1,000w on thin RG-8X if your application from a table using
constants was accurate. At 5 mhz there is considerable cross section of that
small diameter center conductor carrying current. That is why the center
conductors are not paper-thin hollow tubes the way the outer shield _can_
be. Do you agree?

Best,

Jack

 

[Gary Schafer]

Hi Gary, when a poster asked for the formulas for this discussion, I could
not display them in the newsgroup (ascii) so I pasted several of them on a
website.....

http://members.cox.net/pc-usa/station/skineffect.htm



The resistance of a particular conductor, not just it's material, must be
known to calculate skin depth. Averaging it with constants will produce the
wide variety of depths that are seen in different formulas and tables.

Yes it depends on the shape too. A round conductor will be slightly
different than a flat conductor but for our purposes it is in the ball
park. The constant comes from actual calculations. The constant makes
it easier than going through all the math to obtain the constant.

Yes I agreed with you it is relevant only at very high power or long lengths
when inductive reactance becomes as important as DC resistance.

The AC resistance that I am referring to has nothing to do with any
reactance due to cable length. Reactance is of course another factor
that enters into the picture but AC resistance in this case is
referring to that resistance caused by skin effect. Not reactance.

Gary, the problem with using those constants is, again, it will allow you to
reduce the skin depth to nearly nothing, when in fact below a certain cross
section at HF frequencies, formula predictions for skin depth cease to be
relevant. The current, assumed to be constant, cannot continue to use less
and less cross section until it has nothing to work with. The formulas are
an approximation that allows designers to consider the resistance casued by
skin effect and use an appropriately sized conductor. For instance, I could
not use 1,000w on thin RG-8X if your application from a table using
constants was accurate. At 5 mhz there is considerable cross section of that
small diameter center conductor carrying current. That is why the center
conductors are not paper-thin hollow tubes the way the outer shield _can_
be. Do you agree?

RG-8X will get a little warm with 1000 watts on it.
The main reason the center conductors are not paper thin hollow tubes
is because of physical restraints. If your argument would hold up then
none of the hard line coax would have hollow tubing for their center
conductors. Some of it is used in extremely high power at HF as well
as UHF. Only the outer surface of the center conductor is of much
importance in conduction.

While it is true that it gets more complicated to predict actual skin
effect on a thin conductor because as said before, the current does
not completely stop at a certain depth. It decreases exponentially.
But usually 4 or 5 skin depths are sufficient for all practical
purposes.

At that depth of 4 skin depths less than 2% of the current on the
surface will be present. We use .37 as a skin depth but .368 is closer
to what it works out to. .368 x .368 x .368 x .368 = .183 or 1.83%

But I think the original argument was whether or not the same current
or any current would flow on the inside of a copper tube at HF.
It goes away quickly and can't propagate inside as explained earlier.

Regards
Gary

 

[Bruce in Alaska]

snipped because we all know this stuff.......right?

Now how can you argue with that! :>)

Regards
Gary

Gary, I think that your "Beating a Dead Horse" here....Jack just isn't
going to get it. Seems he can't wrap his mind around Physics 101.
Very nice explanations, though.......

Bruce in alaska

 

[Gary Schafer]

snipped because we all know this stuff.......right?




Gary, I think that your "Beating a Dead Horse" here....Jack just isn't
going to get it. Seems he can't wrap his mind around Physics 101.
Very nice explanations, though.......

Bruce in alaska

Thanks Bruce. I do think he has the blinders tightly strapped on.

Regards
Gary

 

[Gary Schafer]

And, if a Navy sailor has used them, the 50 ohm 1/8W resistors are cooked
from having transmitters keyed into the attenuators, too, negating any
possibility of CALIBRATION....Been there, fixed them for years for a
living...(c; Put your ohmmeter from the center pin of the output cable to
the shield and see if it measures 50 ohms....quick test.

Skin effect musta been why RG-8A melted when I keyed those twin 4-1000A
home brew linears I used to build into them...hee hee. I got accused of
hooking them up to the AC line to blow them at my ham club meeting. No,
wait, I think that was "dielectric heating" at 6KW....sorry. RG-17A/U
didn't melt.

You were right the first time. Dielectric loss is not a factor below
100 mhz. Only lack of large enough conductor surface area causes
heating / loss.

Hogwash. They use copper tubing because it's cheap at the local air
conditioner supply house and because, if the station is above 5KW, copper
tubing COOLS itself better because it has a bigger radiating surface than
copper wire of the same cross section. Skin effect is immeasurable at 550-
1600 Khz.....or 20 Mhz, actually. Skin effect starts rearing its head up
in the VHF to UHF range where my 2 meter kilowatt used 2" copper plumbing
tubes and Ts for a plate tank for the 4CX250Bs in push pull.

Nooo ooo, not you too Larry. Did it occur to you that copper tubing
with the same cross section as copper wire has much greater SURFACE
AREA? That would help with cooling and also, believe it or not reduce
skin effect so it didn't get as hot in the first place.

Ever heard of litz wire? I am sure you have. It is often used in small
coils to reduce skin effect losses. And guess what, it is most
effective below frequencies of 1 mhz. So if skin effect was not a
factor at those low frequencies what would be the need for litz wire?

Got any old 10khz or 50 khz coils laying around? I bet you will find
some litz wire in them. The old command set receivers with the 85 khz
IF's are wound with litz wire. Wanna guess why.

Geez, all this time I was told it worked in TEM mode, with the H field
around the center conductor perpendicular to the E field from center
conductor to shield, with the RF flowing up the dielectric, like RF fields
will. I never heard of skin effect at, say, 20 Khz, where coax also works
just fine, properly terminated of course. I'm gonna call WWVB and warn
'em!

Oh I am sure they already know about it!
Next time you are playing with your big amp tuning your mobile
antenna, try swapping out your solid wire loading coil with the same
size copper tubing for a coil and see if either one gets any hotter.
If skin effect doesn't exist then your solid copper coil should be
much cooler of the two.

Regards
Gary

 

[Jack Painter]

It isn't very fancy, actually. The Icom AT-140 tuner is screwed to the top
of the aft cabin just aft of the mizzen mast, which is deck stepped. The
HV RF output post is about 8" from the base of the insulated backstay on
the main and a short, smoothly bent piece of #12 Copperweld antenna wire is
hose clamped to the Amel's backstay jack out of the way of the winch handle
socket. The insulator is about a ft from the mast at the top and every
time I look up there I want an insulator on each end of the triatic stay
with an interconnecting Copperweld wire connecting the top of the backstay
antenna to the center of the insulated triatic to make it a capacitor hat
on top of the 50' sloping vertical for the lower frequency bands. If it
ever goes back into the yard for demasting, it will have it...(c; But, for
now, it just has the backstay.

When Geoffrey got the boat, the previous owner reported poor performance
(he was a ham, too) from the backstay antenna, which I traced down to
loading from the stainless cable topping lift on the large main boom,
sucking off the signal to the mast because when the boom was centered, it
was only a few inches from the backstay. Not good. So, we changed the
stainless to nylon and now no metal gets near the antenna, no matter where
the boom is set. Signal reports came up a LOT!

Directly beneath the tuner, in the support for the deck stepped mast, are
several storage holes I can put wires into. So, I got a #8 battery wire,
black of course, and put a ring terminal to fit the ground post on the
tuner on one end. As straight as I could, I routed it down through the
openings in the mount into the engine compartment which is right under the
mast. Directly under the tuner, too, is the DC shunt used for the ampere-
hour meter on the house batteries under the shunt. This great ground, to
the big 700 AH house batteries against the hull, and the whole house ground
system, is tied in at the shunt, then the cable drops straight down to the
engine block for more grounding and capacitive coupling through the hull.
Antenna current came way up as did signal reports from this installation.
Dropping a bare Copperweld wire over the side I use for even more grounding
while underway at sea, I measure only about 1.5 ohms from the bare wire
laying on the bottom of the marina and this ground connection above.
Something's got a great connection to the ocean down there. I musta got
lucky.

That's it. The radio is grounded to a ground strap Amel installed behind
the panel behind the chart table. It's a common ground strap where all my
instrumentation, navigation and communications is tied with small wire.
There is a direct connection between that strap at the nav station and the
engine block and house ground, too. I like to think it may bypass some
static hits, but haven't been through any on this boat....yet. Let's not
rush the testing of this theory.

Larry W4CSC

Sounds great Larry, Thanks. Seen in a Univ of Florida study, paraphrased:

1. All boats can be struck by lightning, protected or not, and
2. Protected boats and unprotected boats both suffer damage when hit, and
3. Unprotected boats suffer significantly more damage than protected boats.

It sounds like you and Lionheart are well protected.

I remember a night of terrible line squalls that wrecked several yachts in
Block Island Salt Harbor. I had stayed up on deck with gear on as I knew it
was coming as I returned from a night on the town. It was worse than any
summer line squall should have been! By the time I roused my family the
winds had the entire harbor dragging anchor. Anyne who has been there can
imagine the panic of watching your Out Island 41 heading toward mega-million
yachts both dragging along with you, and lining the docks for a busy
weekend. The Westerbeke diesel with one anchor could not hold us, and I went
forward to set a second anchor and lots of chain with it. I think there must
have been hundreds of lightning srtikes all around us without any break
between them. Night turned to day, and that helped avoid touching shrouds
while on deck. Everything around us seemed to be getting hit, and of course
it was one of those moments when (at least I) thought I was going to die
from lightning at any moment. But the second anchor and the diesel held us
just short of one of the hundred-footers at the outer docks. In the
aftermath, we heard there was a lot more damage from collisions than from
lightning, and that is amazing considering how many yachts I saw get struck
that night.

Best,

Jack

 

[Gary Schafer]

I've read the webpage from FL. Very interesting research. The mast looks
tall when you're standing at the bottom of it looking up, but in the
overall height of a thunderstorm FIVE MILES HIGH, our masts are like a
dimple on the dining room table, and not much of a "target".

I was at the transmitter shack of WRJA-TV, the PBS station in Sumter, SC,
visiting an old friend who was chief engineer, Bill Jones, one night. We
were building the first weather radio repeater after Bill had applied for,
and gotten, an FCC license for that band to simply repeat the signal from
Columbia, SC's weather station to the local Sumter area which had trouble
hearing it. We made it out of kit ham radio repeater boards from VHF
Engineering in Binghamton, NY, as we had a local repeater.

A huge thunderstorm cell moved across Sumter and actually went THROUGH the
1800' WRJA-TV tower while we watched out the back door as lightning went
SIDEWAYS 10 miles in the cloud just to hit that big 1800' ground rod
sticking up out of the table-flat terrain of eastern Sumter County. I'm
standing there watching the light show and suddenly Bill taps me on the
shoulder and hands me a big yellow rain coat, saying, "Come on. I wanna
show you something neat." We followed the huge hardline coaxial cables
from the 35KW TV transmitter out to the base of the antenna and Bill says,
"You're standing in the safest place in Sumter County. There is a cone of
protection against being hit by lightning provided by my tower and you're
now standing in the middle of it. Hang onto the tower leg and feel the
current going through it." I burned my hand a couple of times as the huge
BOOMs went off over my head a thousand feet up. The huge bridge cables
JUMPED from the surge of electrical EMP hit them, many times. The lights
went out and we had to go back in the building to reset the transmitters
when the power came back on.

Though the "tower" on the sailboat is very short, in comparison, I like to
think that if you have a proper grounding system, like the professor
describes on his webpages, you are also in a tiny cone where the blast will
mostly be shunted AROUND you, which is why your car is so safe in a
thunderstorm. The current surge that kills goes AROUND the the steel body
of the car....Steel ships and boats do that....Plastic, not so good.

Larry

Larry, I really don't believe you are that dumb to hold on to a tower
in the middle of a lightning storm. I do see that you are a great
story teller though. However please remember that there are a lot of
folks that read this group that may not be too technically savvy and
may not be able to tell the difference.

Regards
Gary

 

[Gary Schafer]

Not dumb at all. Under my feet were 36 pile-driven ground rods connected
with bridge cables to the tower in a ring about 100' in diameter, "driven
to refusal", in other words, bed rock.

The several megohms of body resistance is no path at all when in parallel
with a few MICROOHMS to such a ground system. With currents high enough to
heat the tower beyond what my hand could tolerate, there is no shock, at
all.

It was a most amazing afternoon.....(c;

Larry

With the high current traveling through the tower and the relatively
high impedance that the tower and ground leads present, it is possible
to have thousands of volts differential in only a few feet length. The
larger the tower the less impedance of course. But the ground system
is never 100% and it has it's own impedance problems.

All conductors have impedance and a high current applied to that
impedance will produce a large voltage drop across it. Even the tower
itself.

Ground rods driven past 8 to 10 feet do little good for lightning.
Even if they are into the water table past that depth. The impedance
of that long of a rod gets to high to be of much value. (I know, lots
of people have long deep rods or pipes in their installations and
think they have the best ground in the world)

If you really want to know why go look at the polyphaser site. They
even tell you how to calculate what the voltage drop in a few feet of
tower length will be with a typical lightning strike.

You are right about the tower providing a "cone of protection" but
that cone only means that the lightning will probably strike the tower
before it strikes you directly. It does not tell you anything about
how effective the tower / ground system is at getting the lightning
current dissipated safely to ground.

Don't be grabbing on to those towers during a storm Larry. We will
miss you here.

Regards
Gary

 

[Jack Painter]

I've read the webpage from FL. Very interesting research. The mast looks
tall when you're standing at the bottom of it looking up, but in the
overall height of a thunderstorm FIVE MILES HIGH, our masts are like a
dimple on the dining room table, and not much of a "target".

"You're standing in the safest place in Sumter County. There is a cone of
protection against being hit by lightning provided by my tower and you're
now standing in the middle of it. Hang onto the tower leg and feel the
current going through it." I burned my hand a couple of times as the huge
BOOMs went off over my head a thousand feet up. The huge bridge cables
JUMPED from the surge of electrical EMP hit them, many times.

Though the "tower" on the sailboat is very short, in comparison, I like to
think that if you have a proper grounding system, like the professor
describes on his webpages, you are also in a tiny cone where the blast will
mostly be shunted AROUND you, which is why your car is so safe in a
thunderstorm. The current surge that kills goes AROUND the the steel body
of the car....Steel ships and boats do that....Plastic, not so good.

Indeed. That Florida study explains that there are very few examples of
sailors (on sailboats) being hurt or killed by lightning. That is due to the
cone of protection as you said, but it does not normally extend to anyone
touching those shrouds or mast! To some extent you are bonded to the system
when standing on deck and could be in a very high voltage condition without
feeling much current due to the bonding. While HV lineman aloft use that
principle safely every day, boaters are advised to remain below deck and NOT
touch anything conductive during a lightning storm.

Similarly, while "under" the cone of protection of that high transmitter
mast, you were indeed safe. But on your way over to it and back from it, you
are both lucky you lived to tell the story. The voltage gradient between
your two feet on the walk nearby could be thousands of volts during a
discharge let alone a strike.

Best regards,

Jack

 

[Jack Painter]

======================================

Would that have been in the summer of '74 by any chance? I was
halfway between Mystic, CT and BI that year when we got hit by the
mother of all line squalls just after dark.

It was the summer of '85. I lived in Mystic from '84 to '87 right at the
drawbridge, in what turned out to be the only building on the water that did
not burn from Gravel Street to the drawbridge, a few years back.

Best regards,

Jack