Antenna for Video-Camera-Detector (15 khz)

[watchjohn]

.

I need a antenna for a Video-Camera-Detector
...this is not just for wireless cams
but for all cams...specially the !! WIRED !!

The detector is in fact a receiver for the
horizontal-sync frequency used by all
video-cameras and other video-equipment

For NTSC that is 15734 HZ (15,7 khz)
For PAL that is 15625 Hz (15,6 Khz)

Here is a few detectors..again look for those
doing WIRED cams.

http://tinyurl.com/27y56n

By the way if anyone knows what circuit
is used in that wired-cam detector
or maybe owns one...i would be very interested
what the 15 khz receiver is made of.
Other circuits welcome too.


Back to the antenna:

The whole idea is that...when someone enters
a certain office...there should be an alert
that that someone is carrying a (switched on)
(wired or not) video-camera.

The receiver with antenna could for example
be hidden in a large clock or in a large picture-frame,
mounted on the wall next to the entrance.


=========================
Technical requirements for antenna
=========================



Freq-range:
-----------
15 to 16 khz
(smallest bandwidth possible to supress
out-of-band signals as much as possible)


Size :
------
Fitting inside a clock or poster-frame (max 50 x 50 cm)
wich will be mounted on the wall (other ideas welcome).


Directivity:
------------
Preferred mostly directional
(pointing at the entrance or center of the entrance/hall)
to avoid picking-up signals from the other side of the wall
(video-monitors also sendout 15 khz sigs...and there might
be some unwanted shortwave-VLF breaktrough)


Balanced or Unbalanced:
----------------------
Might depend on receiver
wich i have not choosen yet...actually
still have to find a good circuit.


Impedance:
---------
Also might depend on receiver wich i have not made yet.


Gain:
-----
Highest signal-level as possible (gain)
since signals are very-very weak.


Antenna type:
-------------
Don´t care as long as it works good
according to mentioned specs
Loop,Coil,Ferrite...anything that
fits into max 50 x 50 x 5 cm´s




The receiver will be mounted at the antenna
so antenna connects directly to the receiver
...so active circuit and cable not neccesary.

There is a chance that after first experiments
i find out that i actually receive stronger signals
on the harmonics (2,3,4,5 times 15 khz)
that could be very well possible and depends on
the video-camera and how it is build and the lengths
of the cables connected to it
In that case the antenna should also be at those
higher harmonics...the receiver also ofcourse
...but lets start first at the base-freq.

I might probably use a 567 tone-detector IC
tuned between 15.6 and 15.8 khz.
..these are also used in various
video-squelch or video-operated-switch circuits.

I´m still looking for a very smallband HQ bandpass-filter
with high gain...or a steep saw/dielectric/helical filter.
to maximise gain and out-of-band-rejection.

I have checked out various websites on VLF-reception
wich deal with receiving "natural phenomena"
but have not found a good receiver/detector/antenna
for my purpose yet.

I have also thought of having 2 antennas with 2 receivers
in a differential configuration...that could be handy
to avoid reception of local or external signals.
since i then could balance the system for signals that
are always there...only a new (moving signal)from that
new visitor would cause unbalance and trigger the alarm.


....why do i always want complicated things ?


Thanks in advance again !


WatchJohn


(no this is not for my watch-detector )

 

[MacGyverS2000]

I could pull a camera off of the shelf next to me right now that would give great high-quality color images and not show even a glimmer on the spectrum at 15kHz. Don't make the assumption that because CRTs work at a particular rate that CMOS imagers are going to do the same.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[watchjohn]

.

Hi Dan,

That was a very fast answer ! (4 minutes)

Why don´t you give it a try ?

Take your shortwave-receiver
or connect a line to your soundcard and download
some spectrum analyzing software.

Start with a few turns around the video-cable
...close to the camera.


The point is that:
CMOS or CRT camera it doesn´t make any difference !
since they all have to generate that same
"horizontal-sync" signal...they have to !
otherwise it wouldn´t be a NTSC or PAL signal
and the camera couldn´t give a picture on
a NTSC or PAL monitor.

As a matter of fact every thing that uses NTSC or PAL
standards will emit some signal derived from a strong
component in that video-signal...including video-recorders
and monitors.

In the early days in some countries you had to pay
a tax for having a TV-set

The Tax-department used to check on houses that said
to not have a TV

They used 15 Khz receivers to check if that was true.



Try this one also:

Tune your receiver to 3.58 Mhz (for NTSC)
or 4.43 Mhz (for PAL)

Those are the frequencies of the Xtals (oscillators)
and these can be received also....sometimes even
better the the mentioned 15 kHz signal !

Read this good report on

"How to find hidden cameras"

http://www.tentacle.franken.de/papers/hiddencams.pdf

that is one of the best "camera-detection" papers around.

(by the way he metions other oscillator freqsn also
but forgets about the above mentioned xtal-frequencies)


I know it works (from pratice)

Above technique can also be used for detecting other
equipment...if you know the frequencies that occur in
that equipment...every oscillator is a transmitter.

Your reciver or scanner is a transmitter also.

Even if it´s not a real oscillator but some circuit that
operates at a certain frequency it will emit some radiation
at a radio-frequency that can be received.

Harmonics of those frequencies can also be received
some times even better...depending on for example
the lengths of PCB tracks...the housing...etc


Now lets find a good antenna and receiver-circuit
for my purpose as described.


Greetings


Radiotechscan

 

[VEBill]

"Why don´t you give it a try ?"

Watchjohn - ah, that's YOUR job.

At these frequencies, the antenna would not be critical. The SNR is set by the external environment. Antenna gain brings directivity and thus doesn't really help for this application. There's really no other variable except common sense ones (avoid extreme loss, poor noise figure).

The receiver would be probably based on long integration and looking for a spike in the spectrum.

It's all a wee bit - hmmm, what's the right word? - a wee bit dreamy.

 

[zeitghost]

In the early days in some countries you had to pay
a tax for having a TV-set

The Tax-department used to check on houses that said
to not have a TV

They used 15 Khz receivers to check if that was true.

In the UK they still do... but it doesn't detect the 15kHz or 10kHz (as it was for 405 lines) signal, it detects the local oscillator signal leaking out of the tuner.

 

[MacGyverS2000]

Ah, no...

You're again making a false assumption... that the video output of the camera is NTSC/PAL. The cameras I'm talking about do not output analog video. For another example, try finding an NTSC or PAL signal on an HDMI cable... buried beneath all of the other digital data you're not going to see squat.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[watchjohn]

.


Yes...in case of non-analog or non-NTSC or non-PAL
or non SECAM ...etc it won´t work.


But....

Check out the 1000 spyshops on the net
and show me 1 miniature/pinhole camera
with a real digital ouput (non NTSC or PAL)

So in 99.99999% a analog camera is going to
be used..when we are talking hidden cameras (bodyworn)

So my assumption is not that false really

I bet that even digital cameras that work to a certain standard radiate some common frequencies...you will find
these frequencies on all cams working on that same standard.

Shure you could alsways come up with situations
where my idea is not going to work...fine
but that is not what i asked for.


Greetings


WatchJohn

 

[IRstuff]

see:

http://www.altasens.com

http://www.ovt.com

http://www.micron.com/products/partdetail?part=MT9M001C12STM

All these parts are the wave of the future. The overhead of an external A/D and conditioning circuitry is high and there is no good reason to put them off-chip.

These are the current and next generation cameras, with built in A/D. Not sure where you're getting your "99.99999% a analog camera... is going to be used.



TTFN

FAQ731-376

 

[MacGyverS2000]

If you had something worth stealing by way of video, the last thing I'm going to do is go with a cheap off-the-web solution.

The main point being you're shooting for detecting the standard low-quality COTS stuff, which is fine if you plan to sell to clients who shop out of the back of Popular Mechanics for their surveillance equipment... husbands who want to spy on their wives, voyeurs who want to spy on their neighbors, wanna-be detectives, ultra-paranoids, etc.

But when you look at the higher quality equipment, such as CMOS imagers, spread spectrum bugs, etc., you have little hope of creating an inexpensive device that will reliably detect these items. The people using the higher quality equipment will be protecting real property (trade secrets, confidential communications, and so on), and the bad guys going after this sort of material will not be using Popular Mechanics level spy equipment.

I think you need to either shift your focus towards creating a high-end component and forget about creating compact, reliable, and inexpensive tools or risk wasting your precious time... right now you're creating tomorrow's detectors for yesterday's technology bugs.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[watchjohn]

.

Shure it seems easy to find cams that
produce non-standard formats.

But at the moment these are not offered
at the regular outlets for video-spy-equipment.
i´ve seen thousands of such websites and they
don´t have them...for various reasons:

1) To expensive.
2) No pinhole/covert lens available.
3) No miniature recorder to cope with the format.
4) No miniature recorder at relative low-price.
5) Low-cost analog cams are good enough.


The "regular" spy is going to spend 800 U$ instead
of 15000 U$ for a broadcast-quality-digital cam
with broadcast-quality-digital-recorder...etc

The "regular" holder of worthy information does not
have a AUTOMATIC-WARNING-SYSTEM against people
entering their premises with hidden cams,
not a low-cost and not a high-cost-system,
not for analog and not for digital cams.
simply because it does´nt exist...(i haven´t seen it yet)

As said it´s easier to say that something wont work
if they would use that-and-that equipment
...instead of answering my question for a 15 khz antenna.

I didn´t ask "can you come up with situations where my idea wouldn´t work"

Allthough i can understand and appriciate sceptisism.

I asked for a 15 khz antenna and gave some background
for what it is going to be used for.

I found it already...and have found enough info the last
few days to where to purchase or make them myself.

Finding (wireless)bugs is another story
Spread-spectrum bugs are a piece of cake
...use a simple a wideband-detector. (Diode-detector)

Thanks anyway appriciate your time !



WatchJohn

 

[MacGyverS2000]

You do understand that spread spectrum transmissions are meant to spread the energy over such a large portion of the spectrum that detection of signal energy above the noise floor is difficult, at best, right? Looking at the screen of a spectrum analyzer will show you the same image regardless of you transmitting or not. Unless you have the proper bit sequence to search for, you're going to see nothing but background noise. If you're able to detect a "spread spectrum" item using a simple wideband detector, it sounds more like marketing hype than true SS technology.

And as you said, the "regular spy" isn't going to spend a great deal of money to purchase quality equipment. Just like a regular Joe isn't going to care about protecting what can be stolen with a simple video camera... the big wigs who will care are going to have more important documents and will be attacked by spies with larger budgets than $1,000. They know this and will expect a higher quality of detection equipment, something that your setup in its current form is going to fail to meet.

Just trying to bring a healthy dose of skepticism to the project before you spent too much time going down a road that may be filled with major potholes.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[TheSimo]

....of course mobile phones have been banned from the site?
Who hasn't got a camera integrated mobile phone these days?I wouldn't expect them to be a PAL or NTSC device.

A camera detector bought would become a wasted investment.

Also with a mobile, no need to worry about sneaking in all the extra packaging (wires/Batts etc)reqd for a wired camera, also no need for the infiltrator to worry about the limited range of a wireless camera.