Regarding the potential hazards involved in using raised radials on a
vertical - I'd be interested in comments from readers of this
newsgroup.

The antenna installation proposed is a vertical installed through the
roof of a building. For many reasons it would be preferable to keep
the radials inside the attic. My concern is possible danger due to
the high voltages incurred at the ends of the radials. The antenna
will be a SteppIR vertical for 40-10 meters with the base just under
the roof, protruding through the roof. At the base will be a number
of resonant radials fanning out throughout the attic. My concern is
if this poses a fire hazard due to arcing (corona, whatever) at the
ends of the radials. It may not be convenient to suspend the radials
over their entire length or provide high quality suspended insulators
at the wire ends. So what danger is there in letting radials lay on
the floor of the attic, attached to the roof rafters, or even poked
down inside the studs of the walls? I think we can assume the attic
will be dry, except for normal Seattle humidity !!

Rick K2XT

As a followup to my question, I guess the concept or the question is
no different than if it referred to a dipole instead of radials on a
vertical. The concern is protection from the high voltage at the end
of the wire, and the potential of it causing a fire.
So it is really a very general question, considering the numbers of
antennas hams are having to disguise or hide inside their homes these
days.

Rick K2XT

Unless you run kilowatts you have nothing to worry about. To be on
the safe side. just use thick plastic covered wire for your radials
taking a little extra care at the extreme ends. Inspect every few
years.

If by some very remote chance arcing should occur your SWR meter will
jump about and you will be obliged immediately to investigate whatever
is the cause, radials or anything else.
==================================

If by some very remote chance arcing should occur your SWR meter will
jump about

Good point, thanks for the info.,

If by some very remote chance arcing should occur your SWR meter
will jump about

Good point, thanks for the info.,

----------------------------------------------------------------------
--

Rick, You are welcome.

I have on occasion, for educational reasons and to avoid the many
misunderstandings, recommended a change in the name of the ubiquitous
SWR meter. It does not measure SWR and usually there is no line on
which the SWR purports to be measured. And reflected power is somewhat
meaningless or at least useless information.

However, where it is located, it is an extremely valuable indicating
instrument. I have suggested the name be changed to TLI (Transmitter
Loading Indicator) which it actually is. Unfortunately, there are too
many old wives in the way and it interferes with their ancient,
pre-1950 traditions.
----
Reg, G4FGQ

Rick K2XT wrote:
As a followup to my question, I guess the concept or the question is
no different than if it referred to a dipole instead of radials on a
vertical. The concern is protection from the high voltage at the end
of the wire, and the potential of it causing a fire.
So it is really a very general question, considering the numbers of
antennas hams are having to disguise or hide inside their homes these
days.

In a vertical dipole, you have only one "radial" which carries
the same currents and voltages as the upper vertical element.
Seems to me, when one has multiple radials, the energy in each
radial has to be the total energy available divided by the number
of radials. Therefore, the voltage at the ends of 1/4WL radials
should decrease as the number of radials is increased.

This seems to be another way that distributed networks differ
from lumped circuits. We might even be able to calculate the
voltage at the ends of the radials, given the number of radials
and the total power available to the radial system.
--
73, Cecil http://www.qsl.net/w5dxp


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Cec, don't you think you should take diameter of radials as well as
their number into account. Also their angle, and the height above
ground, or their distance from the brickwork, roof beams and rafters
when in an attic.

Do you have an equation for Volts = Function( number, frequency,
watts, length, diameter, angle, height, etc ) ?
----
Reg, G4FGQ

Reg Edwards wrote:
Cec, don't you think you should take diameter of radials as well as
their number into account. Also their angle, and the height above
ground, or their distance from the brickwork, roof beams and rafters
when in an attic.

Actually, I was thinking free space when I wrote that. It
was a qualitative answer, Reg, not a quantitative one.

Do you have an equation for Volts = Function( number, frequency,
watts, length, diameter, angle, height, etc ) ?

Only a ballpark figure, Reg, which should be good enough.
Since balanced radials don't radiate (much), it should
be a piece of cake for you to come up with a piece of
software that calculates voltage at the tips Vs number
of radials. Let me know if you need any help. :-)
--
73, Cecil http://www.qsl.net/w5dxp

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Rick,
One thought - I'd be very concerned about RF getting into the entire house
system, especially stereos and tv's, depending on how your "radials" align
with house wiring and how proximate they are. I had a dipole 15 feet off the
roof of my house and at 1 KW, it wasn't a pretty sight...burglar and fire
alarms going off, night lights blinking (the KW is on a separate 220 line),
stereo speakers talking donald duck...the whole house rebelled. So now I am
repositioning it out in the back pasture. The only alternative is QRP!
73,
Greg, N6GK

"Rick K2XT" wrote in message
...
Regarding the potential hazards involved in using raised radials on a
vertical - I'd be interested in comments from readers of this
newsgroup.

The antenna installation proposed is a vertical installed through the
roof of a building. For many reasons it would be preferable to keep
the radials inside the attic. My concern is possible danger due to
the high voltages incurred at the ends of the radials. The antenna
will be a SteppIR vertical for 40-10 meters with the base just under
the roof, protruding through the roof. At the base will be a number
of resonant radials fanning out throughout the attic. My concern is
if this poses a fire hazard due to arcing (corona, whatever) at the
ends of the radials. It may not be convenient to suspend the radials
over their entire length or provide high quality suspended insulators
at the wire ends. So what danger is there in letting radials lay on
the floor of the attic, attached to the roof rafters, or even poked
down inside the studs of the walls? I think we can assume the attic
will be dry, except for normal Seattle humidity !!

Rick K2XT

"Cecil Moore" wrote:
Reg Edwards wrote:
Do you have an equation for Volts = Function( number, frequency,
watts, length, diameter, angle, height, etc ) ?

Only a ballpark figure, Reg, which should be good enough.
Since balanced radials don't radiate (much), it should
be a piece of cake for you to come up with a piece of
software that calculates voltage at the tips Vs number
of radials. Let me know if you need any help. :-)
________________

Reg,

The 1937 Brown, Lewis and Epstein IRE paper "Ground Systems as a Factor in
Antenna Efficiency" include an analysis of the currents in radial ground
systems, along with equations and graphs for it in various configurations.
All you need to do to apply them to a system of raised radials is to modify
these basic equations.

Of course, you will have to read the paper first to do that (wink, nudge).
But then you might also see why knowledge of ground conductivity was
unimportant to the conclusions of this paper, and refrain from saying so in
the future.

RF