From 1969 to at least 1994, the US Embassy in Russia had listening devices (in-depth).

On Thursday, November 16, 2017 at 1:55:43 AM UTC-5, wrote:
From 1969 to at least 1994, the US Embassy in Russia had listening devices (in-depth).

There have always been listening devices and there always will be.

I remember reading the clever way the Russians were snooping on the Americans with no bugs within half a mile of the room: they targeted a laser on a window pane of the room they were spying on. The window pane acted like a microphone diaphragm. They then demodulated the return signal which had the room audio modulated on it. Probably not hifi but I'll bet it was usable.

Gotta give them props for that trick.

John-Del wrote:

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


There have always been listening devices and there always will be.

I remember reading the clever way the Russians were snooping on the Americans with no bugs within half a mile of the room: they targeted a laser on a window pane of the room they were spying on. The window pane acted like a microphone diaphragm. They then demodulated the return signal which had the room audio modulated on it. Probably not hifi but I'll bet it was usable..


** By all accounts, bouncing a IR laser off a widow is not practical. The beam has to be precisely aligned *square on* to the window and the resulting sound quality is abysmal.

OTOH this simple Soviet invention worked well and had no such issues:

https://en.wikipedia.org/wiki/The_Th...stening_device)



..... Phil

On 16/11/2017 12:07, John-Del wrote:
On Thursday, November 16, 2017 at 1:55:43 AM UTC-5, wrote:
From 1969 to at least 1994, the US Embassy in Russia had listening devices (in-depth).

There have always been listening devices and there always will be.

I remember reading the clever way the Russians were snooping on the Americans with no bugs within half a mile of the room: they targeted a laser on a window pane of the room they were spying on. The window pane acted like a microphone diaphragm. They then demodulated the return signal which had the room audio modulated on it. Probably not hifi but I'll bet it was usable.

Gotta give them props for that trick.


Reminds me of a project , I never got around to trying.
I had a pot of those glass beads that are used in the paint of road
traffic signs. Since originally thinking about the idea , paint-ball
guns are now around. But the idea was to somehow propel a blob of white
paste and beads upwards and then down, to splat onto a window pane,
leaving a simulated bird **** hit. Then try a laser beam at any angle
onto the bird **** and monitor the return.

On 16/11/17 12:29, Phil Allison wrote:
John-Del wrote:

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


There have always been listening devices and there always will be.

I remember reading the clever way the Russians were snooping on the Americans with no bugs within half a mile of the room: they targeted a laser on a window pane of the room they were spying on. The window pane acted like a microphone diaphragm. They then demodulated the return signal which had the room audio modulated on it. Probably not hifi but I'll bet it was usable.


** By all accounts, bouncing a IR laser off a widow is not practical. The beam has to be precisely aligned *square on* to the window and the resulting sound quality is abysmal.

I don't understand that. Why "square on"? Wouldn't the beam have a
tendency to pass right through the glass, with little reflection?
Wouldn't it be best to have it meet the glass above the critical angle,
so it would experience maximum reflection? Of course, the detector would
then have to be well away from the laser, and aligning them would be
very difficult.

And in these days of double and triple glazing, it would be even less
viable.

OTOH this simple Soviet invention worked well and had no such issues:

https://en.wikipedia.org/wiki/The_Th...stening_device)

Thanks for that link. A very interesting read.

--

Jeff

Jeff Layman wrote:

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


** By all accounts, bouncing a IR laser off a widow is not practical.
The beam has to be precisely aligned *square on* to the window and
the resulting sound quality is abysmal.


I don't understand that. Why "square on"?


** The IR laser and its receiver have to be in the same location, maybe hundreds of yards away rom the target window, so alignment is near impossible.

Google the idea.



..... Phil

On Thu, 16 Nov 2017 04:29:12 -0800 (PST), Phil Allison
wrote:

** By all accounts, bouncing a IR laser off a widow is not
practical. The beam has to be precisely aligned *square on*
to the window and the resulting sound quality is abysmal.

This might help:
"Laser Bounce Listening Device"
http://gbppr.dyndns.org/~gbpprorg/mil/laserl/index.html
See Fig 9 and associated text, which discusses the angles of incidence
and reflection.

In my never humble opinion, there are several reasons why it is better
to use a laser source and detector at the same location.
1. Any common mode vibration of the laser and detector mounting would
cancel if they are mounted on a common surface.
2. It's much easier to build a small interferometer than one with a
large baseline.
3. Coated

On the other foot, there is a good reason to use a large reflection
angle:
1. Reflections are limited by Brewster's angle. Beyond some angle,
al the light is reflected. Below this angle, little is reflected and
the laser beam ends up going through the glass and bouncing around the
room.
2. Since the reflected light becomes polarized, a polarized filter
will reduce optical "noise" pickup from the sun and other sources of
light pollution.

I've tried this a few time, but never bothered to try it with dual or
triple pane windows. I don't think it will make much difference
because I can hear street noises through my double pane windows with
little difference over a nearby single pane window. Both panes
probably move together.

OTOH this simple Soviet invention worked well and had no such issues:
https://en.wikipedia.org/wiki/The_Thing_(listening_device)

Yeah, that was really clever. However, I'm told that RF reflections
off of anything moving and metallic in the room made listening
difficult. At 330MHz, the transmit antenna beamwidth would have
covered the entire room and possibly much of the building. Later
models worked at microwave frequencies, which offered a narrower
beamwidth.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Thu, 16 Nov 2017 04:29:12 -0800 (PST), Phil Allison
wrote:

** By all accounts, bouncing a IR laser off a widow is not
practical. The beam has to be precisely aligned *square on*
to the window and the resulting sound quality is abysmal.

This might help:
"Laser Bounce Listening Device"
http://gbppr.dyndns.org/~gbpprorg/mil/laserl/index.html
See Fig 9 and associated text, which discusses the angles of incidence
and reflection.

In my never humble opinion, there are several reasons why it is better
to use a laser source and detector at the same location.
1. Any common mode vibration of the laser and detector mounting would
cancel if they are mounted on a common surface.
2. It's much easier to build a small interferometer than one with a
large baseline.
3. Coated

On the other foot, there is a good reason to use a large reflection
angle:
1. Reflections are limited by Brewster's angle. Beyond some angle,
al the light is reflected. Below this angle, little is reflected and
the laser beam ends up going through the glass and bouncing around the
room.
2. Since the reflected light becomes polarized, a polarized filter
will reduce optical "noise" pickup from the sun and other sources of
light pollution.

I've tried this a few time, but never bothered to try it with dual or
triple pane windows. I don't think it will make much difference
because I can hear street noises through my double pane windows with
little difference over a nearby single pane window. Both panes
probably move together.

OTOH this simple Soviet invention worked well and had no such issues:
https://en.wikipedia.org/wiki/The_Thing_(listening_device)

Yeah, that was really clever. However, I'm told that RF reflections
off of anything moving and metallic in the room made listening
difficult. At 330MHz, the transmit antenna beamwidth would have
covered the entire room and possibly much of the building. Later
models worked at microwave frequencies, which offered a narrower
beamwidth.

That is a good question: can ground-penetrating-emitted waves be bent or corrupted easier than waves within a laser beam?

Anywho, with a hard-wire connection (on the other hand) like with high-speed internet, isn't interference more easily detected (and less possible to apply)? Here, electrodes would have to be applied to the window or some other part of both the transmitting and receiving locations. Electrodes (I guess) like the ones doctors use to attach to the skull to determine brain signals, like if they wanted to merely create the sensation of smoking, drinking, doing drugs, etc..) without it actually being done.

On Sat, 18 Nov 2017 06:21:17 -0800 (PST),
wrote:

Yeah, that was really clever. However, I'm told that RF reflections
off of anything moving and metallic in the room made listening
difficult. At 330MHz, the transmit antenna beamwidth would have
covered the entire room and possibly much of the building. Later
models worked at microwave frequencies, which offered a narrower
beamwidth.

That is a good question: can ground-penetrating-emitted waves be
bent or corrupted easier than waves within a laser beam?

How easier RF is refracted (bent) or reflected varies with frequency,
material, density, magnetic field, etc. In other words, just about
everything you can put between the transmitter and receiver. For GPR,
the frequency is important as different frequencies penetrate
different materials in varying degrees. This chart sorta helps:
http://www.geophysical.com/antennas.htm
If you wanted to go through concrete, I would guess(tm) that 400 Mhz
would be about right. I don't have any experience with GPR, so I
don't know if this is correct.

However, we're not going through anything. The laser is being
reflected off of the surface, probably through a Low-E reduced heat
loss coating, and back to a receiver. The ideal surface would be a
mirror. The worst surface would be an RF transparent glass or plastic
window.

The exact opposite is true for the microphone RF cavity and antenna
contrivance. The RF has to penetrate the building or window, reflect
off the side of the cavity, go back through the building or window,
and somehow end up at the receiver. In this case, the ideal building
material would be totally transparent to RF. That's not going to
happen, so the best they could do was use lower frequencies, such as
300 Mhz, which sorta goes through building materials. However, the
frequency was probably selected because the cavity inside the seal had
to be big to pickup voice, and the optimum physical size that would
fit worked out to about 300 MHz.

Anywho, with a hard-wire connection (on the other hand) like with
high-speed internet, isn't interference more easily detected (and
less possible to apply)?

Why would I want to detect interference?

Here, electrodes would have to be applied to the window or some
other part of both the transmitting and receiving locations.

I suspect the embassy staff might have noticed the electrodes and
wires. Stealth means a listening device cannot be easily detected.

Electrodes (I guess) like the ones doctors use to attach to the
skull to determine brain signals, like if they wanted to merely
create the sensation of smoking, drinking, doing drugs, etc..)
without it actually being done.

You just walked off the deep end. I have no idea what you're
suggesting or asking. Please bug someone else.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Phil Allison writes:


OTOH this simple Soviet invention worked well and had no such issues:= 20

https://en.wikipedia.org/wiki/The_Th...stening_device)

Little Gem was not in the Embassy; it was in Spaso House.

--
A host is a host from coast to
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Jeff Liebermann wrote on 11/17/2017 1:47 PM:
On Thu, 16 Nov 2017 04:29:12 -0800 (PST), Phil Allison
wrote:

** By all accounts, bouncing a IR laser off a widow is not
practical. The beam has to be precisely aligned *square on*
to the window and the resulting sound quality is abysmal.

This might help:
"Laser Bounce Listening Device"
http://gbppr.dyndns.org/~gbpprorg/mil/laserl/index.html
See Fig 9 and associated text, which discusses the angles of incidence
and reflection.

In my never humble opinion, there are several reasons why it is better
to use a laser source and detector at the same location.
1. Any common mode vibration of the laser and detector mounting would
cancel if they are mounted on a common surface.

I believe you have that wrong. If the laser and detector vibrate the same
in the direction toward/away from the reflector, the vibrations add, not
subtract.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

On Thu, 4 Jan 2018 18:15:08 +0000 (UTC), David Lesher
wrote:

Phil Allison writes:


OTOH this simple Soviet invention worked well and had no such issues:= 20

https://en.wikipedia.org/wiki/The_Th...stening_device)

Little Gem was not in the Embassy; it was in Spaso House.

What does this have to do with electronics repair?
Take it to an appropriate newsgroup.....

On 1/7/18 2:04 PM, wrote:
What does this have to do with electronics repair?
Take it to an appropriate newsgroup.....

Thank you.
Here's your official "Junior Net Nazi" badge.
(.)


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

On 11/17/2017 01:30 AM, Phil Allison wrote:
Jeff Layman wrote:

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


** By all accounts, bouncing a IR laser off a widow is not practical.
The beam has to be precisely aligned *square on* to the window and
the resulting sound quality is abysmal.


I don't understand that. Why "square on"?


** The IR laser and its receiver have to be in the same location, maybe hundreds of yards away rom the target window, so alignment is near impossible.

Google the idea.



.... Phil


It's one of those ideas that sounds both plausible and really clever
except for the small detail that it doesn't work. Like extracting audio
from ancient times off the decorative grooves cut into clay pots while
spun on a wheel

On 01/08/2018 11:26 PM, bitrex wrote:
On 11/17/2017 01:30 AM, Phil Allison wrote:
Jeff Layman wrote:

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


** By all accounts, bouncing a IR laser off a widow is not practical.
The beam has to be precisely aligned *square on* to the window and
the resulting sound quality is abysmal.


I don't understand that. Why "square on"?


** The IR laser and its receiver have to be in the same location,
maybe hundreds of yards away rom the target window, so alignment is
near impossible.

Google the idea.



....Â*Â* Phil


It's one of those ideas that sounds both plausible and really clever
except for the small detail that it doesn't work. Like extracting audio
from ancient times off the decorative grooves cut into clay pots while
spun on a wheel

There are a lot of ways to skin that particular cat, and normal
incidence isn't required. Oblique incidence and a remote quad-cell
photodiode in another nearby building is perfectly doable. The transmit
laser would have a fast 2D scanner, and a separate data link would allow
closing a feedback loop to keep the reflected beam centred on the quad
cell. What the sound quality would be like, I don't know.

A fast, fine raster scan would allow lock acquisition in a few seconds.

Adaptive optics is used for much harder jobs than that, every day.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com