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'[EE] TV detection'
2007\12\16@074504 by Spehro Pefhany

picon face
At 05:32 AM 12/16/2007, you wrote:
>Does anyone know how TV detection works?
>http://www.derbygripe.co.uk/tv.htm
>I have been pondering and still coming out clueless...
>John

(tag changed to EE)

The most obvious way is to detect local oscillator emissions, which will
be offset from the channel by the IF frequency. See, for example,
US 2896070 (1956) which has nice illustrations of a van with an
antenna.

It's also possible to insert a signal at the transmitter and detect
EMI from the video signal to a CRT. See, for example, US 4635109, but
I doubt that it would work with an LCD.

I suspect there's a signature of SMPS emissions that could be used to
detect stations based on the gross pattern of dark/light on a channel. We
used a variation of that method years ago to visually detect which channel
TV sets in high-rise apartments half a mile away were tuned to-- you could
not make out any details of the screen, but it wasn't hard to figure out which
channel it was when you could see the light emissions.

And, perhaps other methods (see, for example, what you can from the Tempest
program). And even a bit of light can be used..

https://www.publications.cl.cam.ac.uk/316/01/ieee02-optical.pdf

And there are non-electronic methods, both passive (such as using a database
of people who don't have a licence/license, as suggested by many in the UK)
and active (e.g. inject a "signal" by sending a letter or three, then
compare the responses of a person accused of cheating with a standard
profile). ;-)

(PS. I mentioned a couple of US patents, which in turn have a bunch of
other cites. One focus of US work is gathering information of commercial
value on who is watching what. Obviously the frequencies and so on would be
somewhat different for UK television systems, but the same principles would
generally apply).

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2007\12\16@163608 by Jinx

face picon face
> I don't know if this was a legal requirement but it certainly happened -
> & even (especially ?) in those days I objected to it

IIRC someone took a stand on the grounds that it wasn't actually
compulsory to pay for a licence. A passive resistance movement
started, with the intention of clogging the courts *. But I don't recall
if that was the reason the licence was scrapped. Probably helped,
although I was surprised the government didn't just change the law

And put the fee up for good measure ;-)

* there are/were also quiet background stirrings about the entire
NZ tax system not being ratified. There is/was a legal opinion that
it was introduced solely as a war fund (WWI ?) and should have
been re-legislated after that

2007\12\16@163609 by Jinx

face picon face
> It's analogous to putting a loud speaker in a park somewhere and
> try to charge people a fee just because they can hear the music as
> they walk by

In NZ there have been several successful outcomes for APRA
(the Australasian Performing Rights Assoc) getting royalties from
businesses that have music playing, either as background or for
the staff, that the public, eg customers, can hear

2007\12\16@165103 by David VanHorn

picon face
> In NZ there have been several successful outcomes for APRA
> (the Australasian Performing Rights Assoc) getting royalties from
> businesses that have music playing, either as background or for
> the staff, that the public, eg customers, can hear

Yup.. Muzak (the elevator music) company does that here.  They have
people who covertly visit retail stores, and if the store is playing a
radio or CD music, then the store gets a visit from an RIAA person who
explains the matter and the fines.  Then the store gets a visit or
call from a Muzak salesperson.  Very cute.

2007\12\16@170837 by Jinx

face picon face
> Very cute.

Wonder if anyone would dare try that with a party ?

"Shut that music up or we'll call the cops"
"Yeah, go on then"
"OK, we'll call APRA"
"Alright, we'll be good"

2007\12\16@171733 by Mario Mendes Jr.

flavicon
face
right, but the record companies can't put the loud speakers in public and
then charge the fee as people walk on by.  If you put the speaker out, then
they can charge YOU, for using their material for public use, but not charge
the people that walk by and hear the music.

--------------------------------------------------
From: "Jinx" <.....joecolquittKILLspamspam@spam@clear.net.nz>
Sent: Sunday, December 16, 2007 4:23 PM
To: "Microcontroller discussion list - Public." <piclistspamKILLspammit.edu>
Subject: Re: [EE] TV detection

>> It's analogous to putting a loud speaker in a park somewhere and
>> try to charge people a fee just because they can hear the music as
>> they walk by
>
> In NZ there have been several successful outcomes for APRA
> (the Australasian Performing Rights Assoc) getting royalties from
> businesses that have music playing, either as background or for
> the staff, that the public, eg customers, can hear
>
> --

2007\12\16@172220 by David VanHorn

picon face
On Dec 16, 2007 5:07 PM, Jinx <.....joecolquittKILLspamspam.....clear.net.nz> wrote:
> > Very cute.
>
> Wonder if anyone would dare try that with a party ?
>
> "Shut that music up or we'll call the cops"
> "Yeah, go on then"
> "OK, we'll call APRA"
> "Alright, we'll be good"

Probably too fast to get anyone out there.
But I know that's what Muzak did,  I worked for Muzak.  My end was
keeping all those amplifiers repaired, and telephone systems, and...

2007\12\16@174538 by Jinx

face picon face

> right, but the record companies can't put the loud speakers in
> public and then charge the fee as people walk on by

Well, they could try ;-) Step One would be easy enough. Step
Two will probably get them the result they expect

You can't force people to pay for something they didn't ask for
(generally, if you accept that people pay bulk taxes and have no
say in how it's spent specifically)

Might get it to work in N Korea, broadcasting Kim Il-Sung

(studiously avoiding Letterman's perennial Kim Jong-Il joke)




2007\12\16@182554 by Mario Mendes Jr.

flavicon
face

>> right, but the record companies can't put the loud speakers in
>> public and then charge the fee as people walk on by
>
> Well, they could try ;-) Step One would be easy enough. Step
> Two will probably get them the result they expect
>

But I seriously doubt this would stand in a court of law in the US. The
closest to this I can see is something like a concert where people pay to go
watch the show, but they go by their own choice, and it's a closed venue,
where they chose to go and pay.  It is no longer someone just blaring music
in public with the purpose of forcing bystanders to pay.


2007\12\16@214844 by John Chung

picon face

--- Spehro Pefhany <EraseMEspeffspam_OUTspamTakeThisOuTinterlog.com> wrote:

> At 05:32 AM 12/16/2007, you wrote:
> >Does anyone know how TV detection works?
> >http://www.derbygripe.co.uk/tv.htm
> >I have been pondering and still coming out
> clueless...
> >John
>
> (tag changed to EE)
>
> The most obvious way is to detect local oscillator
> emissions, which will
> be offset from the channel by the IF frequency. See,
> for example,
> US 2896070 (1956) which has nice illustrations of a
> van with an
> antenna.
>
 Thanks Spehro, sounds a standard method into TV
detection. I now have some clue where to hunt for info
now.

>
> And, perhaps other methods (see, for example, what
> you can from the Tempest
> program). And even a bit of light can be used..
>
>
www.publications.cl.cam.ac.uk/316/01/ieee02-optical.pdf
>
 Possibly a newer method but it is out of my grasp
right now.... Interesting read though.

Thanks,
John Chung



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2007\12\16@221427 by Zik Saleeba

face picon face
On Dec 17, 2007 1:48 PM, John Chung <kravnusspamspam_OUTyahoo.com> wrote:
>
>   Thanks Spehro, sounds a standard method into TV
> detection. I now have some clue where to hunt for info
> now.

The other method I've heard involves tuning in to the IF frequency.
Then you can use a directional antenna to pick out which house is
watching which station. By displaying the signal you can see exactly
what they're watching and be sure that you're not just picking up a
spurious emission of some sort on what you thought was an LO
frequency.

Cheers,
Zik

2007\12\17@022350 by Dr Skip

picon face
Aren't TV IFs in the hundreds of kHz? That would make any sort of directional
antenna many tens of meters long/wide at least... No? Not only that, the
discrimination between houses at those wavelengths from the street seems
impossible, either in the E or H plane.

Even if it were a couple of MHz, that's about 100m wavelength...

Can one contest the accusations arrived at from such techniques?


Zik Saleeba wrote:
{Quote hidden}

2007\12\17@025101 by Richard Prosser

picon face
IIRC a TV IF used to be about 36MHz. New sets probably use a variety of IFs
- much the same as radios have moved from the "std. 10.7 & 455kHz" IF
frequencies..

Also, I seem to remember rthat the earliest detector vans used to use the
line frequency emissions from the yoke/CRT and a largish rotatable loop
antennae to detect unlicenced  TVs.

RP

On 17/12/2007, Dr Skip <KILLspamdrskipKILLspamspamgmail.com> wrote:
{Quote hidden}

> -

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