Self-demodulation
Eckard Blumschein
directed sound beams. This effect has been predicted from
Khokholov-Zabolotskaya-Kusnetsov parabolic wave equation
and experimentally verified as a result of dissipation in a
thermoviscous fluid for 10-MHz pulses in carbon tetrachloride.
Could it be possible that a similar self-demodulation occurs for
the 1,500-MHz electromagnetic field of a phased array radar
acting within the endolymphatic fluid of the inner ear, in particular
near to ion channels on top of the stereocilia, in other words,
in close proximity of tectorial membrane?
JosephShore23
>From: Eckard Blumschein blums...@et.uni-magdeburg.de
>Date: 01/07/02 6:59 AM Eastern Standard Time
>Message-id: <3C398DBA...@et.uni-magdeburg.de>
Yes. Then again...... JS
Jim Deutch
news:3C398DBA...@et.uni-magdeburg.de...
I don't think the EM field can self-demodulate here: that requires
non-linear effects, and I don't think any such are forthcoming in the
specified environment.
Such EM fields, however, can cause sound waves via periodic heating of
tissues. These might be a better candidate for demodulation.
Jim Deutch
franz heymann
Eckard Blumschein <blums...@et.uni-magdeburg.de> wrote in message
news:3C398DBA...@et.uni-magdeburg.de...
Your question prompts another one: Where would a 1.5 GHz signal in
the ear come from?
Be that as it may, such a signal would have a free-space wavelength of
2cm, and a phased array would be at least of that size in free space.
Fitting such an array into the ear would imply quite unbelievable
values for either the permittivity or the permeability of the stuff in
the ear. And, in order to provide demodulation it would have to be
non-linear to boot.
My server does not recognise alt.sci.physics.acoustic, so I hope you
don't mind my adding an s at the end
Franz Heymann
Eckard Blumschein
> Your question prompts another one: Where would a 1.5 GHz signal in
> the ear come from?
>
> Be that as it may, such a signal would have a free-space wavelength of
> 2cm, and a phased array would be at least of that size in free space.
> Fitting such an array into the ear would imply quite unbelievable
> values for either the permittivity or the permeability of the stuff in
> the ear. And, in order to provide demodulation it would have to be
> non-linear to boot.
My question has a serious background. There there is mounting evidence
for phased array radars to cause perception of a hum. This hum has been
annoying many people in several countries. The US name is Taos hum.
Even if pulse power of an air port radar may exceed 1 MW, just a small
part if it hits the ground. I am aware of measured electric field strength
of 100 V/m inside a building to be multiplied by a correction factor of
about 100 due to 300 ms integration time. In that case frequency was
3 GHz corresponding to 10 cm wavelength. Frequency of a phased array
radar might be as low as 1500MHz, corresponding to 20 cm. Of course,
the antenna is huge as compared to the inner ear.
You are quite right. Demodulation always requires non-linearity.
The simplest idea is to ascribe a thermal effect. However, this would
not immediately take into account that hair cells are much more
sensitive than other tissue. So I am looking for a possibly more tricky
kind of coupling from changing intensity of HF energy into steered
ion inflow into the cilia. I rather imagine an involvement of the
non-linear behavior of the hair cells. KZK equation also describes
a non-linear effect.
Eckard Blumschein
> I don't think the EM field can self-demodulate here: that requires
> non-linear effects, and I don't think any such are forthcoming in the
> specified environment.
>
> Such EM fields, however, can cause sound waves via periodic heating of
> tissues. These might be a better candidate for demodulation.
Well, this is the common interpretation of what has been summarized
in my message M102 at
http://iesk.et.uni-magdeburg.de/~blumsche/AuditoryFunction.html
However, some people seem to be very sensitive against the stimulation by
radar. Maybe, this peculiarity can completely be attributed to the brain.
I would just like to exclude more basic phenomena. We were told that
stimulation of the hair cells always results from bending of the cilia.
This might be questionable because this is merely one method to change
the inflow of ions. In contrast to the notion by Hudspeth, the tip links do
not have lids to be mechanically lifted but they rather deform more or
less oval shaped key holes. Without tension of the tip links, the ion
channels were found (M119) to be open.
robert egri
As far as I understand EM, neither the quality nor the quantity of the
field depends on whether it is generated by a phased arrary or by an
aperture or by a reflector antenna. So you can just ignore that and
concentrate only on EM effects of the inner ear. The freespace
wavelength is 20cm at 1.5GHz but within the human body that will
change and can be much smaller.
The pulse rate of a pulsed radar can be anywhere from a few kHz to a
few hundred kHz dependending on its range (longer ranges, lower pulse
rate, usuallly), and 1.5GHz is a fine cooking frequency. So if
periodically you heat up your ear at say 10kHz, I guess you may even
have some sensation of hearing the pulse rate or some integer harmonic
thereof.
(The correction factor of 100 and 300 msec integration with 1MW EIRP
resulting in 100V/m is very obscure)
franz heymann
Yes, I did miss a zero when I said it would have a wavelength of 2 cm
> Of course,
> the antenna is huge as compared to the inner ear.
>
> You are quite right. Demodulation always requires non-linearity.
> The simplest idea is to ascribe a thermal effect. However, this
would
> not immediately take into account that hair cells are much more
> sensitive than other tissue. So I am looking for a possibly more
tricky
> kind of coupling from changing intensity of HF energy into steered
> ion inflow into the cilia. I rather imagine an involvement of the
> non-linear behavior of the hair cells. KZK equation also describes
> a non-linear effect.
My apologies. I misunderstood you. This is the phrase which foxed
me:
" the 1,500-MHz electromagnetic field of a phased array radar acting
within the endolymphatic fluid of the inner ear, "
I interpreted this as a suggestion that you were envisaging an antenna
within the ear.
Now that I understand what you mean, my comment is that it would not
be all that surprising if there were some object in the auditory
system which is capable of producing some rectified component from
the very large fields associated with a high power radar system. The
demodulated signal would then have a frequency which is related to the
repetition rate of the transmitted pulses. Surely it should be
possible to ascertain how the hum frequency compares with the rep.
rate of the nearby radar set without having to ask any questions to
the operators of the radar?
And indeed, your suggestion of a thermal effect might have some merit.
Franz Heymann
Eckard Blumschein
>my comment is that it would not be all that surprising if there were
>some object in the auditory system which is capable of producing
>some rectified component from the very large fields associated
>with a high power radar system.
Yes, I was told puls frequency is clearly audible. I am however not
sure wether this perception is actually based on mechanical rectification
as usually.
>The demodulated signal would then have a frequency which is related
>to the repetition rate of the transmitted pulses. Surely it should be
>possible to ascertain how the hum frequency compares with the rep.
>rate of the nearby radar set without having to ask any questions to
>the operators of the radar?
Strangely, frequency of the hum does not at all fit to the repetition rate.
The hum phenomenon merely occurs fairly distant from the antenna.
Perhaps hum frequency relies on vertical frequency.
>And indeed, your suggestion of a thermal effect might have some merit.
Of course, unless sensitivity could probably be higher against a more
direct stimulation. Duration of each pulse is as small as about one
microsecond. So thermal energy is tiny.
robert egri wrote:
> As far as I understand EM, neither the quality nor the quantity of the
> field depends on whether it is generated by a phased arrary or by an
> aperture or by a reflector antenna. So you can just ignore that and
> concentrate only on EM effects of the inner ear. The freespace
> wavelength is 20cm at 1.5GHz but within the human body that will
> change and can be much smaller.
In case of a phased array, side lobes strongly depend on angular
position. This might explain why people do not hear a brief ton
each time they are hit from main lobe but a rather strange hum.
Notice, the main lobe is not directed towards ground even if
there is certainly reflection from temperature inversions, etc.
we do not know yet whether a reflector antenna is also audible,
perhaps not. Sudden increase of the number of complaints
apparently coincides with introduction of phased array technology.
What about EM effects on the inner ear, I wonder if MRT is not
also to blame for that.
Yes, deformation of the EM field within the wet tissue of the
human body might be important for modelers. Someone already
pointed to the circular canal filled with very special fluid,
reminding of an induction loop.
> The pulse rate of a pulsed radar can be anywhere from a few kHz to a
> few hundred kHz dependending on its range (longer ranges, lower pulse
> rate, usuallly), and 1.5GHz is a fine cooking frequency.
I was already informed that phased array radars are distinguished by
just 1.5 GHz, and from first measurement as well as from reported
"slowly beating" of the hum I conclude that vertically scanning
radars have a comparatively slow rate of rotations per minute.
> So if
> periodically you heat up your ear at say 10kHz, I guess you may even
> have some sensation of hearing the pulse rate or some integer harmonic
> thereof.
Well, some of the suffering people have been reporting a high tone
besides the hum, perhaps corresponding to pulse rate. I have to add
that the hum is only audible in silent environment, typically inside
a bedroom. I derive from some indications that perception of the hum
is not based on spectral analysis.
> (The correction factor of 100 and 300 msec integration with 1MW EIRP
> resulting in 100V/m is very obscure)
I refer to a paper by A. Enders, professor for EMI in Braunschweig, Germany.
He used an electric field meter EMR300 by Wandel and Goltermann
together with a RMS E field probe in order to perform isotropic measurement
up to 3 GHz. Enders concluded from 42 ms exposition time out of 5 seconds
for a complete revolution and 300 ms integration time that the measured
power is reduced by a factor of 7.2. Pulse width of 1 microsecond together
with 1.2 kHz repetition rate means once again a reduction by 833.
833 times 7.2 equals a power ratio of 6000, that is a reduction of E by the
factor 77. I apologize for my incorrect recall.
The corrected value was 100 V/m inside an office but 400 V/m on the roof.
Power was 1.5 MW. Distance from the antenna was about 1.5 km.
Such high values were suddenly measured for about nine days. Then E
also suddenly stepped down to an intermediate value for five days and
once again further down for the rest of recorded time. I was told that
possibly the operator changed the frequency channel. Does this provide
a realistic explanation?
Harry Conover
Hey Eckard. Don't give up your day job! OK?
Out of pure curiousity, why a phased array radar? If what you propose
is fact (not very likely) wouldn't an SPS-49 pulsed shipborne radar,
or for that matter a common airport radar, have seriously more
profound effects?
Also note that you are off by several orders of magnitude in regard to
the frequency at which most fixed and shipborne phased array radars
generally operate. Do web searches using the search pattern "AN/SPY-1"
and "Pave Paws" to comprehend what I'm suggesting. Systems like these
operate in the high VHF to middle UHF frequencies, but not at the
1,500-MHz band you cite. (Not to say that some airborne, rear
illuminated, PARs don't exist, but these are not likely to be a
problem to you for rather obvious reasons.)
Harry C.
Eckard Blumschein
> Hey Eckard. Don't give up your day job! OK?
Could you please get more specific in a private mail?
> Out of pure curiousity, why a phased array radar? If what you propose
> is fact (not very likely) wouldn't an SPS-49 pulsed shipborne radar,
> or for that matter a common airport radar, have seriously more
> profound effects?
Admittedly I am not familiar with radar systems. Radar was just one
candidat under trial. Initially may speculations blamed real sources
of sound, the industrial power grid, cellular phones, Schuman resonance,
etc. for the hum. However, only radar was consistent with a variety of
ubiquitously reported features. Apparent pitch was the same in the US
as in Europe despite of 60/50 Hz. There is considerable dependency
on the whether. Records of electromagnetic field were made over several
hours. They exhibits the same tendency as did subjective assessment of
hum strength. Three suffering people with covered eyes demonstrated
how intensity of the hum periodically goes up and down a few times each
minute. Zoom of the measured electromagnetic field revield that these
fluctuations occur with high regularity and just in the ballpark of known
rpm of radars. There was actually a radar nearby.
Why phased arrays?
1st reason: Massive complaints near Stuttgart started rather suddenly.
Maybe, they coincided with introduction of a modern system.
2nd reason: Normal airport radars might have less side lobes.
I imagine that their main lobe just illuminates each point around for
a few milliseconds. So one would not perceive a hum. I was told
that operators hear rather the pulse frequency.
3rd reason: The hum would be plausible as a result from vertical
scan. I was confirmed that modern radars with vertical scan are
based on phased array systems.
4th reason: Since radar fields are very strong and undoubtedly
audible, I did not restrict my consideration to radars of the
largest power.
> Also note that you are off by several orders of magnitude in regard to
> the frequency at which most fixed and shipborne phased array radars
> generally operate. Do web searches using the search pattern "AN/SPY-1"
> and "Pave Paws" to comprehend what I'm suggesting. Systems like these
> operate in the high VHF to middle UHF frequencies, but not at the
> 1,500-MHz band you cite. (Not to say that some airborne, rear
> illuminated, PARs don't exist, but these are not likely to be a
> problem to you for rather obvious reasons.)
Radar frequency was not yet identified. Perhaps, it doesn't matter much, at all.
The 1.5 GHz relate to the FPS-117.
Harry Conover
> Harry Conover wrote:
>
> > Hey Eckard. Don't give up your day job! OK?
>
> Could you please get more specific in a private mail?
>
> > Out of pure curiousity, why a phased array radar? If what you propose
> > is fact (not very likely) wouldn't an SPS-49 pulsed shipborne radar,
> > or for that matter a common airport radar, have seriously more
> > profound effects?
>
> Admittedly I am not familiar with radar systems. Radar was just one
> candidat under trial. Initially may speculations blamed real sources
> of sound, the industrial power grid, cellular phones, Schuman resonance,
> etc. for the hum. However, only radar was consistent with a variety of
> ubiquitously reported features. Apparent pitch was the same in the US
> as in Europe despite of 60/50 Hz. There is considerable dependency
> on the whether. Records of electromagnetic field were made over several
> hours. They exhibits the same tendency as did subjective assessment of
> hum strength. Three suffering people with covered eyes demonstrated
> how intensity of the hum periodically goes up and down a few times each
> minute. Zoom of the measured electromagnetic field revield that these
> fluctuations occur with high regularity and just in the ballpark of known
> rpm of radars. There was actually a radar nearby.
If the sound claimed to be perceived is a power line frequency hum, I
believe RADAR systems can be safely excluded as the source. This is
simply because the power-line ripple component is almost totally
lacking in the system's radiation signature. A microwave over, having
only minimal ripple filtering, hence producing heavily power frequency
modulated RF, would be a far better candidate.
For some introductory information on how Phased-Array Radars actually
function, I stongly suggent reading Eli Brookner's excellent article
on the subject in the February, 1985 issue of Scientific American.
(The cover featured article.)
An excellent intermediate level reference to both Phased-Array Radars,
and RADAR systems in general, is Brookner's text: "Radar Technology",
ARTECH HOUSE, INC., Dedham, Massachusetts, 1980 (and later editions).
Just as examples of large, fixed, Phased-Array RADARS installations:
PAVE PAWS (AN/FPS-115), has two radiating faces, each 72.5-feet in
diameter,
operates in the 300-MHz range, with an average power output of 145-KW,
and peak power of 585-KW. Each face has 1792 active elements, and 885
dummy elements.
It's unclassified range is 3,000-Nautical-Miles.
COBRA DANE (AN/FPS-108) operates near 1,000-MHz, has 15,360 active and
34,768 passive elements, and is claimed to have the ability to track
an object the size of a marble at 1,000-Nautical-Miles. Operating
power is 15-MW.
The 1.5-GHz you attribut the the FPS-117 is likely correct but,
unfortunately I have no information on this particular system availabe
here at home.
> Why phased arrays?
>
> 1st reason: Massive complaints near Stuttgart started rather suddenly.
> Maybe, they coincided with introduction of a modern system.
Certainly a credible reason.
> 2nd reason: Normal airport radars might have less side lobes.
> I imagine that their main lobe just illuminates each point around for
> a few milliseconds. So one would not perceive a hum. I was told
> that operators hear rather the pulse frequency.
This is incorrect. Large Phased-Array Radars produce the lowest
intensity side-lobes of any type RADAR. Details of how this is done
remain classified, but the fact that a very large number of dummy
elements are included in the arrary to accomplish this end is
unclassified and freely published. I'm sure that you realize that,
like a telescope, the face diamater and number of elements plays a
sifnificant role in determining the resolving capacity of such radars,
and consequently the narrowness of the beam.
Most airport radars exhibit relatively poor side-lobe characteristics,
and generally emit a vertically fan-shapped beam to equally illuminate
aircraft flying at many different altitudes. Most of these, but not
all totally lacked altitude determining capability (although a few
rare 3-d systems do). Airport RADARS, for the most part, include a SSR
(Secondary Surveilance Radar) device that interrogates the
plane-installed transponder to obtain their only source of altitude
and other information from the aircraft.
If it were possible to "hear" a RADAR via human physiology, which I
personally believe except very exceptional circumstances to be
unlikely, a conventional airport search RADAR should be much more
likely to produce the phenomenon IMHO.
This would sound like the RADARS characteristic PRF, frequently heard
on car radios when passing very close to an airport RADAR. This is
usually in the 1,00-2,000-Hz audio range. Turn off the radio and the
sound vanishes.
> 3rd reason: The hum would be plausible as a result from vertical
> scan. I was confirmed that modern radars with vertical scan are
> based on phased array systems.
First, most search RADARS with 3-D capabilities are of the
stacked-beam design. This techniques does not generally involve any
vertical scanning, and altitude determination is based on which of a
number of feed-horns the aircraft's RADAR has the highest intensity.
Phased-Array techniquest are employed on a number of Precision
Approach Radars (PARs), but these are generally short-range systems
operating at a very modest power level. I believe that most of the
PARs rely on a rather complex algorithm operating under computer
control to make an alititude determination, rather than employing a
fixed vertical scan rate. This is not to say that it is never done
that way -- only that I have never seen it done that way.
In general, you won't generally find 3-D RADAR in use at many
airports. Where it is found is at locations where the RADAR must serve
a dual-role, with its air defense role alone justifying presence of
the relatively costly 3-D capabilities.
> 4th reason: Since radar fields are very strong and undoubtedly
> audible, I did not restrict my consideration to radars of the
> largest power.
Having had nearly 40-years of engineering expience, much of which
directly dealt with extremely powerful RADAR systems, I know of no
situation in which operation of the RADAR was ever demonstrably
audible to anyone -- even in RF fields strong enough to significantly
elevate body temperature after as short as a 5-minite exposure.
Hence, I tend to be very skeptical of the effect.
I would also like to retract the following statement, since it's
obviously untrue. For some reason I had a mental lapse (likely due to
cumulative effects of the RF I've absorbed over the year). I misread
your 1,500-MHz as 1,500-GHz, since in RADAR we generally speak in
terms of either GHz or operating frequency band (C, L, X, Ku, etc.).
> > Also note that you are off by several orders of magnitude in regard to
> > the frequency at which most fixed and shipborne phased array radars
> > generally operate. Do web searches using the search pattern "AN/SPY-1"
> > and "Pave Paws" to comprehend what I'm suggesting. Systems like these
> > operate in the high VHF to middle UHF frequencies, but not at the
> > 1,500-MHz band you cite. (Not to say that some airborne, rear
> > illuminated, PARs don't exist, but these are not likely to be a
> > problem to you for rather obvious reasons.)
Large shipboard radars frequently operate in the C and L bands, so
frequencies between 1-3-GHz are not at all uncommon. Existing large
Phases-Array RADARS operate at the frequencies I cited in the opening
few paragraphs, but Phased-Arrays operating as high as X-Band (circa
10-GHz) have been proposed and many do exist.
> The 1.5 GHz relate to the FPS-117.
This certainly wouldn't surprise me.
Kindest regards.
Harry C.
Eckard Blumschein
Thank you for your detailed reply. I understood your scepticism.
However, meanwhile there is overwhelming evidence for radar
to be blamed for the mysterious hum.
> If the sound claimed to be perceived is a power line frequency hum, I
> believe RADAR systems can be safely excluded as the source. This is
> simply because the power-line ripple component is almost totally
> lacking in the system's radiation signature.
There are overlooked aspects: The radiation signature has to be
extended to space, and the pulses are hitting different locations of
atmosphere at different time. If there is a strong inversion of temperature,
then the hum is worst.
> The 1.5-GHz you attribut the the FPS-117 is likely correct but,
> unfortunately I have no information on this particular system availabe
> here at home.
I would appreciate getting informed concerning further candidates.
> This is incorrect. Large Phased-Array Radars produce the lowest
> intensity side-lobes of any type RADAR. Details of how this is done
> remain classified, but the fact that a very large number of dummy
> elements are included in the arrary to accomplish this end is
> unclassified and freely published. I'm sure that you realize that,
> like a telescope, the face diamater and number of elements plays a
> sifnificant role in determining the resolving capacity of such radars,
> and consequently the narrowness of the beam.
As a layman I imagine phased array airport systems roughly operating
in broadside mode. I this wrong?
> Most airport radars exhibit relatively poor side-lobe characteristics,
> and generally emit a vertically fan-shapped beam to equally illuminate
> aircraft flying at many different altitudes. Most of these, but not
> all totally lacked altitude determining capability (although a few
> rare 3-d systems do). Airport RADARS, for the most part, include a SSR
> (Secondary Surveilance Radar) device that interrogates the
> plane-installed transponder to obtain their only source of altitude
> and other information from the aircraft.
Suffering people meanwhile tend to blame every air port. I would like
to know whether there are systems that cannot evoke the hum.
> If it were possible to "hear" a RADAR via human physiology, which I
> personally believe except very exceptional circumstances to be
> unlikely, a conventional airport search RADAR should be much more
> likely to produce the phenomenon IMHO.
> This would sound like the RADARS characteristic PRF, frequently heard
> on car radios when passing very close to an airport RADAR. This is
> usually in the 1,00-2,000-Hz audio range. Turn off the radio and the
> sound vanishes.
The last word in that matter have the people concerned. They sometimes
also report a high tone but they are suffering from the hum.
> First, most search RADARS with 3-D capabilities are of the
> stacked-beam design. This techniques does not generally involve any
> vertical scanning, and altitude determination is based on which of a
> number of feed-horns the aircraft's RADAR has the highest intensity.
Are the different stacks pulsing at a time or one by one?
> Phased-Array techniquest are employed on a number of Precision
> Approach Radars (PARs), but these are generally short-range systems
> operating at a very modest power level. I believe that most of the
> PARs rely on a rather complex algorithm operating under computer
> control to make an alititude determination, rather than employing a
> fixed vertical scan rate. This is not to say that it is never done
> that way -- only that I have never seen it done that way.
Because density of radar systems is large in Germany, we cannot
be sure. However, it seems as if typical range of hum is in the ballpark
of 2 to 20 miles. Nominal range might be quite different.
> In general, you won't generally find 3-D RADAR in use at many
> airports. Where it is found is at locations where the RADAR must serve
> a dual-role, with its air defense role alone justifying presence of
> the relatively costly 3-D capabilities.
I guess, this role was taken into account in Germany, too..
> Having had nearly 40-years of engineering expience, much of which
> directly dealt with extremely powerful RADAR systems, I know of no
> situation in which operation of the RADAR was ever demonstrably
> audible to anyone -- even in RF fields strong enough to significantly
> elevate body temperature after as short as a 5-minite exposure.
> Hence, I tend to be very skeptical of the effect.
Please find an old survey in M102 at
http://iesk.et.uni-magdeburg.de/~blumsche/AuditoryFunction.html
Audition is actually intriguing.
> I misread
> your 1,500-MHz as 1,500-GHz, since in RADAR we generally speak in
> terms of either GHz or operating frequency band (C, L, X, Ku, etc.).
As a layman, I have to apologize.
Kindest regards,
Eckard
Harry Conover
> As a layman I imagine phased array airport systems roughly operating
> in broadside mode. I this wrong?
This is likely incorrect, although I don't understand what you mean by
"broadside mode."
The direction and pattern of radiation (and reception sensitivity)
from a fixed location Phased-Array RADAR is entirely determined by the
vector sum of all of its many radiating elements. In most cases this
takes the form of a highly focused pencil shaped beam, but there are
some rare exceptions that I won't muddy the water by describing
(ROTHR, etc.).
In the general case, many individual radiating elements are mounted on
a planar surface. Each element of the array (or groups of elements) is
driven by RF that is of a unique phase and intensity, as controlled by
a computer. The RADAR beam is defined by the far-field vector
summation of the radiation from each contributing element. The
resulting beam from such systems if referred to as having "electronic
agility" since the direction of radiation is instantly modifiable
under electronic (computer) control. No physical movement of the
antenna is required to alter the direction in which the RADAR is
momentarily "looking." This allows planar RADAR face to radiate and
receive from directions up to 90-degrees, from a perpendicular to its
face, in both azimuth and elevation.
> Suffering people meanwhile tend to blame every air port. I would like
> to know whether there are systems that cannot evoke the hum.
Even before RADAR became commonplace, some people claimed that they
heard a hum at various locations on the earth. I suspect that these
same "hum sensitive" people may be now pointing fingers at RADAR
systems, although reports of hum predated the invention of RADAR by
many years. If I recall correctly, Scientific American carried an
article on "atmospheric hum" some years back, but I can't offer a
specific reference.
Regarding claims of hum caused by RADAR, it would seem to me that the
first research experient to be undertaken by a competent researcher
would be to determine that the claimed hum was produced by radiation
external to the body, and not simply an localized physiological
manifestation, such as tintinitis (sp?), e.g., the ringing sound that
some individuals suffer with. A simple Faraday Cage experiment would
seem to me as the logical first step.
> Are the different stacks pulsing at a time or one by one?
With respect to multiple feed-horn 3-D RADAR:
The transmitted beam is generally a fan in the vertical plane, so that
objects at all altitudes are illuminated. The stacked horns function
to determine the elevation of return reflections, i.e., their
customary importance is in receiving.
Harry C.
Tom Shaw
used to describe the direction of the radiated field maximum(a) of any
antenna but it is often used in discussing phased arrays. It refers to
whether the maximum lobe of the pattern is normal to the physical axis of
the antenna or not. Of course in the case of electronically steered
antennas I guess the notion is moot. I am not sure if both of these
adjectives are used with vertical antennas since end-fire would describe a
beam straight up.
TS
"Harry Conover" <hhc...@yahoo.com> wrote in message
news:7ce4e226.02011...@posting.google.com...
Eckard Blumschein
>This is likely incorrect, although I don't understand what you mean
>by "broadside mode."
> I dont know for sure if this is germane but broadside and end-fire are words
> used to describe the direction of the radiated field maximum(a) of any
> antenna but it is often used in discussing phased arrays. It refers to
> whether the maximum lobe of the pattern is normal to the physical axis of
> the antenna or not. Of course in the case of electronically steered
> antennas I guess the notion is moot. I am not sure if both of these
> adjectives are used with vertical antennas since end-fire would describe a
> beam straight up.
> TS
Of course, I have to apologize for confusing broadside and endfire.
Well, I am a layman in so far that I have to guess, a typical phased array
air port radar reminds of a plane square or hexagonal table of maybe 1.5 m
"diameter" and contains several hundreds of elementary antennas.
In principle I would be easily able to calculate the far field. When I wrote
broadside and meant endfire, I imagined that a tiny error in phase has a
large impact on the main lobe angle relative to the ground. I also just guess,
MEMS are used for control. And I suspect, they might be sensitive, e.g.
against humidity.
Harry Conover wrote:
(snip) > there are some rare exceptions that I won't muddy the water by
>describing (ROTHR, etc.).
I would just like to know what ROTHR stands for.
(Snip)
>> Suffering people meanwhile tend to blame every air port. I would like
>> to know whether there are systems that cannot evoke the hum.
>Even before RADAR became commonplace, some people claimed that
>they heard a hum at various locations on the earth. I suspect that these
>same "hum sensitive" people may be now pointing fingers at RADAR
>systems, although reports of hum predated the invention of RADAR by
>many years. If I recall correctly, Scientific American carried an
>article on "atmospheric hum" some years back, but I can't offer a
>specific reference.
In that case you are entirely wrong. If you are reading German, look at
www.brummt.de, being currently hit more than 90,000 times. We made
decisive progress while the discussion on TAOS hum in the US has a
long standing tradition. In 1993 a commission of Congress failed to reveal
the cause. Similar efforts in the UK (LFNSA), the Netherlands, Danmark
(enemies of infrasound) and elsewhere looked for infrasound as the
suspected cause. Actually, sound of low frequency is also quite annoying.
If there was an Article in Scientific American, then it was written in vain.
Nobody knows how many people will get sensitive against the hum
phenomenon. A man who lives in Canada near Seattle telled that 7 out
of 16 People are affected. About 2% were reported from TAOS.
About 500 are registered in Germany. They live near air ports or
military bases.
>Regarding claims of hum caused by RADAR, it would seem to me that
>the first research experient to be undertaken by a competent researcher
>would be to determine that the claimed hum was produced by radiation
>external to the body, and not simply an localized physiological
>manifestation, such as tintinitis (sp?), e.g., the ringing sound that
>some individuals suffer with. A simple Faraday Cage experiment would
>seem to me as the logical first step.
So called competent research institutes have totally failed due to their
limited horizons, while collaborative effort of laymen thoroughly
dealt with a wide variety of observations, ideas, and sucessful experiments.
The so called simple Faraday cage experiment was not required and will
not be helpful while there is compelling evidence for the hum to be caused
by an external source, being largely the same around the globe but being
subject to local whether condition. The source causes a perception that
fully coincides with the temporal pattern of the measured em field with
respect to (radar rotation) period and daily fluctuation of strength, being
obviously dependent on atmospheric conditions for scattering.
Admittedly, marginal persons are still driven by abstruse phantasy.
However, when the radar became the major candidat of suspicion,
it turned out to tally with the whole wealth of seriously noticed observations.
Incidentally, the well known tinnitus, which affects millions of people,
is clearly distinguished from the genuine hum by many features.
>> Are the different stacks pulsing at a time or one by one?
>With respect to multiple feed-horn 3-D RADAR:
>The transmitted beam is generally a fan in the vertical plane, so that
>objects at all altitudes are illuminated. The stacked horns function
>to determine the elevation of return reflections, i.e., their
>customary importance is in receiving.
I am sorry for being still not yet able to exactly understand
how to read this with respect to my question. I imagine that each horn
covers a certain part of vertical range. How many horns are stacked?
Is it correct to ínfer that they are fed one by one because otherwise
the name was not multiple feed?
robert egri
> Tom Shaw wrote:
>[.....]
Relocatable Over The Horizon Radar
Harry Conover
Correct.
ROTHR is an incredibly interesting system to anyone with serious
technical interests.
ROTHR employs both transmitting and receiving arrays that consist of
precisly parallel vertical towers aligned in a row. The transmitting
and receiving arrays may be co-located or in separate locations
separated by nominally 10-50 miles apart.
It is a phased array only in the same sense that a directional
broadcasting radio station also employs a phased array consisting of a
number of vertical towers all being fed at various phased and
intensities in order to to achieve coverage of their local reception
area, while protecting against radiation invading the space of another
broadcaster some distance removed (but operating on the same
frequency).
The primary difference is that ROTHR programs the various phase and
intensity contributions of it many towers accordingy to a computer
programmed scanning scenario. It's a really neat system, in that it
programs transmission frequency to determine the range (propagation
distance is determined by the frequency of the transmitted waves)
while the direction of scan is determine by the phasing of the
antennas.
Transmission involve a limited focus fan produced by the use of a
limited number of in-line, vertical transmission towers. Transmission
employs a number of towers far (almost an order of magnitude) less
that that of the receiving array, since precision azimut of a target
is determined solely by the receiving array.
Without referring to a reference, IIRC the transmission array is
consist of about 30 towers, and the receiving array about 300 towers
spaced in a line about 4-miles in length. (Please don't quote me on
the number of towers until I have an opportunity to check on actuals.)
Little details like these often elude me.
For an engineer, ROTHR is an enormously interesting system. First, it
is a RADAR backscatter system. The signal is transmitter in a very
specific direction, is refracted by the atmosphere in accorance with
the frequency, srikes land or sea, with the backscatter returned to
the receiver over the same path. This gives the RADAR an effective
range of about 1,500-miles, enabling one ROTHR site in Northern
Virginia to track ships and aircraft involved in drug trafficing in
the Caribbean. Stealth doesn't help these guys, since it is sea
backscatter that is being metered, and a stealthy aircraft simply
shows up as a dark blob against a bright backgound on systems of this
type.
It's interesting to not that the fundamental priciples of sytems like
ROTHR go many years back, since the electronics and signal propagation
characters were largely textbook by the mid-1950s. Still, realizing
that the backscattered RADAR signal, after a nearly 4,000-mile round
trip is pretty well down in the noise level, it was not until the
arrival of advanced computer-based signal processing technology
arrived (largely based on multiple DSPs), that systems of this type
became practical, and technical terms like Adaptive and Kalman filters
became nearly household words in certain communities.
Harry C.
Harry Conover
> I dont know for sure if this is germane but broadside and end-fire are words
> used to describe the direction of the radiated field maximum(a) of any
> antenna but it is often used in discussing phased arrays. It refers to
> whether the maximum lobe of the pattern is normal to the physical axis of
> the antenna or not. Of course in the case of electronically steered
> antennas I guess the notion is moot. I am not sure if both of these
> adjectives are used with vertical antennas since end-fire would describe a
> beam straight up.
> TS
Hi Tom,
Being a former Ham, I'm quite familiar with what you are saying, at
least in the context of conventional antennas (Yagi, Slot, Long Wire,
Rhombic, etc.).
Perhaps because of some form of myopia, I simply couldn't equate
"broadside" with the operation of any Phased-Array RADAR antenna with
which I have familiarity, although I am very acquainted with the term
in connection with Ham antennas.
I think the leap is is that when I think of Ham or conventional
broadcasting antennas, which are indeed phased and intensity
controlled, but on a fixed basis (and I earned much of my college
money by consulting with a.m. radio stations to tweek their
directional arrays into FCC compliance after the FCC issued them a
citation). Phased array RADARs are quite a different breed of animal.
Most of these employ hundred, in some thousands, of separate array
elements, each controllable in intensity and phase under constant
computer control, to achieve their functionality.
What I think of as phased array RADAR constitue a very special beast.
Their individual radiating elements are ususally mounteed in a 2-D
configuration on a planar surface. Each element, or groups of
elements, and in continual computer control to establish radiation
direction. The same old rules apply, "But believe me Dorothy, we're
not in Kansas anymore!"
That's is precisly why I could not relate "Broadside" or "Endfire" to
discussion involving RADAR systems.
The "Hum" is something else. Never been there...Never seen or heard
it...Nor has anyone else I know. That's what makes me so VERY
skeptical of it being a real physical effect!
Harry C.
Harry Conover
> Harry C.,
>
> Thank you for your detailed reply. I understood your scepticism.
> However, meanwhile there is overwhelming evidence for radar
> to be blamed for the mysterious hum.
In which case, I'd urge you to reseach the subject to your heart's
content. From my perspective, I have no intererest in further
discussing this subject since you have presented no compelling
evidence for RADAR to be blamed for the mysterious hum, while I at the
same time have have failed to uncover any physics associated with
RADAR that could be reasonably accused as having responsibility for
the claimed manifestation.
I see no useful purpose being served by continuing the dialogue.
Harry C.
Tom Shaw
indicate that broadside and endfire were concepts which would not be
applicable to electronically steered antennas.
Your discussion is very clear.
Harry Conover
> rge...@netscape.net (robert egri) wrote in message news:<b4e32a30.02011...@posting.google.com>...
> > Eckard Blumschein <blums...@et.uni-magdeburg.de> wrote in message news:<3C43EBD0...@et.uni-magdeburg.de>...
> > > Tom Shaw wrote:
> > >[.....]
> > > I would just like to know what ROTHR stands for.
> > > [....]
> >
> >
> > Relocatable Over The Horizon Radar
>
> Correct.
>
> ROTHR is an incredibly interesting system to anyone with serious
> technical interests.
Please forgive both the spelling and other language shortcomings in
the above and a few other of my posts. I was incredibly hurried at the
time I was posting, plus today I post using Google which lacks a
spell-check utility.
Internet veterans understand the drill, and the justifications for it
that date back to the 300-baud dialup, acoustic coupler modem days.
Newbies often lack a clue regarding the trade-offs us old farts
commonly make between immediacy and perfection.
Harry C.
Eckard Blumschein
led to a detour. My question did focus on demodulation because
the human performance obviously once again goes far beyond
what narrow minded engineers are ready to believe.
It looks as if those who got hypersensitive may not just hear
1 W/m^2 but much less. I tend to blame a combination of
the hair cells' nonlinearity, motility, and stochastic resonance for that.
Those who are interested in aspects concerning auditory function
are invited to
http://iesk.et.uni-magdeburg.de/~blumsche/AuditoryFunction.html
Those who are interested in more general questions might look at
www.brummt.de