Ground Or Not To Ground Receiving Antenna In Storm ?
 

Russ wrote:

Doesn't the delta P of a fuel-air bomb travel at greater than the
speed of sound?

No.

Roy Lewallen, W7EL

Ground Or Not To Ground Receiving Antenna In Storm ?
 

The denotation is supersonic, while the flame spread is subsonic.

"Roy Lewallen" wrote in message
...
Russ wrote:

Doesn't the delta P of a fuel-air bomb travel at greater than the
speed of sound?

No.

Roy Lewallen, W7EL

Ground Or Not To Ground Receiving Antenna In Storm ?
 

On Sun, 18 Dec 2005 12:39:09 -0800, Roy Lewallen
wrote:

Russ wrote:

Doesn't the delta P of a fuel-air bomb travel at greater than the
speed of sound?

No.

Roy Lewallen, W7EL

The definition of dentonation includes the flame front moving at
supersonic speeds.

http://www.globalsecurity.org/milita...itions/fae.htm

R

Ground Or Not To Ground Receiving Antenna In Storm ?
 

Russ wrote:
On 18 Dec 2005 08:41:47 -0800, wrote:


I do believe that any mechanical wave, such as a pressure or shock
wave,
travels at the speed of sound, no more and no less. To travel faster,
it
would have to be an electromagnetic wave.

Also, the deaf person wouldn't hear the mechanical wave. Well,
unless they had "some" hearing still available. If it was proven that
a totally deaf person could hear it, that would pretty much nail it
down as
electromagnetic. If that came out to be true, then Coffmans theory
about the auditory nerve picking it up would probably be true unless
some other nerve was actually involved.
MK


Doesn't the delta P of a fuel-air bomb travel at greater than the
speed of sound?

R

Also, the pressure wave INSIDE a rifle barrel travels faster than the
speed of sound. It produces velocities of the projectiles at Mach 3 to
Mach 4. Hmmm...

The air pressure profile on an aircraft wing shows supersonic, transonic
and subsonic reponses. Hmmm..

It raises a physics question. How does the velocity of sound vary in a
compressible medium as the temperature, volume and pressure change?

Ground Or Not To Ground Receiving Antenna In Storm ?
 

Russ wrote:
On Sun, 18 Dec 2005 12:39:09 -0800, Roy Lewallen
wrote:


Russ wrote:

Doesn't the delta P of a fuel-air bomb travel at greater than the
speed of sound?

No.

Roy Lewallen, W7EL


The definition of dentonation includes the flame front moving at
supersonic speeds.

http://www.globalsecurity.org/milita...itions/fae.htm

Yes, I can understand the flame front moving faster than sound, if it's
not a pressure wave. I don't know the mechanism, but presume it's
propagated by radiant heat. That is, a flame occurs, and its heat
radiates and superheats nearby material, causing it to flame. That would
be propagation by electromagnetic wave, i.e., infrared "light". The
radiation would travel at the speed of light, with the apparent speed of
the front being dictated by how fast the material is heated and ignited
by the radiated heat. Propagation by this mechanism and at this speed
would end as soon as the flame front reached the outside of the vapor
cloud, beyond which the resulting pressure wave would travel at the
speed of sound.

I'm not an expert at this, but I'm quite sure that the only way you can
get a mechanical wave to travel faster than sound is if the behavior of
the air becomes nonlinear at some compression level. That could
conceivably happen as a result of an explosion, but I don't think so. If
anyone has any references describing such nonlinear behavior, I'd love
to learn more about it.

Roy Lewallen, W7EL

Ground Or Not To Ground Receiving Antenna In Storm ?
 

"Robert11" wrote
is it better to just leave the now "floating" antenna alone,
or is it better to ground one end of it ?
______________

Most MW broadcast stations use series-fed, insulated towers that usually are
(by far) the highest structures in the area. These stations operate
successfully in lightning storms using a combination of means. First is an
arc gap connected across the tower feedpoint to a very low resistance earth
ground (120 1/4-wave, buried radials). The gap is set to flash over at some
margin above the peak voltage present during normal operation. They also
use a "static drain choke" to earth ground, which is a high Z at the MW
frequency, but doesn't let high static potentials develop on the tower. The
last part of the protection system is supplied by transmitter circuitry that
senses instantaneous phase changes in transmission line current, and kills
r-f output for some milliseconds so as not to sustain any arc that occurs in
the antenna system.

Maybe some of these techniques could be useful in amateur radio
installations.

RF

Ground Or Not To Ground Receiving Antenna In Storm ?
 

Roy Lewallen wrote:
I'm not an expert at this, but I'm quite sure that the only way you can
get a mechanical wave to travel faster than sound is if the behavior of
the air becomes nonlinear at some compression level.

Carrier velocity is linear and must be taken into account. Relative
to a measurement point at the center of the earth, sound waves
traveling East in the surface atmosphere are moving faster than
Mach 2. Do the carriers move during an explosion?
--
73, Cecil http://www.qsl.net/w5dxp

Ground Or Not To Ground Receiving Antenna In Storm ?
 

"Robert11" wrote
is it better to just leave the now "floating" antenna alone,
or is it better to ground one end of it ?
______________

In anticipation of a thunder storm just leave it floating. Not that it
will prevent a direct lightning strike but it MIGHT prevent damage to
equipment and, more important, to yourself.

But it is advisable not to attempt to disconnect it using bare fingers
during the progress of a thunder storm. I am a little superstitious
so I use the XYL's rubber kitchen gloves.

There's only one thing you can be absolutely certain of - lightning
exactly obeys the Mathematical Laws of Probability.

See the works of Sir Ronald Arthur Fisher, the greatest statistician
of all time. Beautifully explained in plain English. He dabbled mainly
in Genetics, Agriculture, the Weather, and the mathematics thereof.
But I'm not aware of anything specifically he had to say about the
statistics of lightning strikes. You will have to work things out for
yourself. In all probability nothing seriously will happen to YOU. So
don't worry about it.

Just DON'T fly kites using 1/2-wavelength metal wires during thunder
storms. Not even on the 10m band. Or shelter from the rain under
solitary trees. It's asking for trouble but you probably won't get
any.

As for me, I'm 80 years of age, and I'm still alive. I've never won
the national lottery. But perhaps that can be explained by the fact
that I've never entered it.

I hope the foregoing has helped to set your mind at rest.
----
Reg, G4FGQ
==========================================

Ground Or Not To Ground Receiving Antenna In Storm ?
 

Reg Edwards wrote:
. . .
See the works of Sir Ronald Arthur Fisher, the greatest statistician
of all time. Beautifully explained in plain English. He dabbled mainly
in Genetics, Agriculture, the Weather, and the mathematics thereof.
But I'm not aware of anything specifically he had to say about the
statistics of lightning strikes. You will have to work things out for
yourself. In all probability nothing seriously will happen to YOU. So
don't worry about it.
. . .
As for me, I'm 80 years of age, and I'm still alive. I've never won
the national lottery. But perhaps that can be explained by the fact
that I've never entered it.

I hope the foregoing has helped to set your mind at rest.

I'd be willing to wager that there are places in Florida which have more
lightning strikes in a single summer than have occurred at your QTH (or
mine) in the past 80 years.

Roy Lewallen, W7EL

Ground Or Not To Ground Receiving Antenna In Storm ?
 

"Reg Edwards" wrote
In anticipation of a thunder storm just leave it floating. Not that it
will prevent a direct lightning strike but it MIGHT prevent damage to
equipment and, more important, to yourself.
.... etc etc removed by major clippage
I hope the foregoing has helped to set your mind at rest.
__________

Possibly you thought this relevant to the original post. But then why not
thread it so, rather than to mine?

RF