[exodust]

Surely this can't be real any more!

Like the wikipedia article says, modern digital signals and flat screens means correlating a set's emissions with a particular licensed broadcast is "difficult"!

I'd say impossible. For a van parked outside to determine you're watching BBC and not something else? Laughably impossible! Unless they peep through your windows?

[rjmunro]

> watching BBC and not something else

You're not allowed to watch "something else" either - it's a national tax on televisions, not a BBC subscription charge.

Historically the detector vans tuned in to the local oscillator frequency generated by the television's "Heterodyne" tuning circuits. In order to tune to different channels, the TV generated different frequencies and used them to shift the broadcast an intermediate frequency to where they would decode it. If you know the intermediate frequency used by the TV (I believe they all use the same one), and can measure the local oscillator frequency, you know the channel being tuned to. You may well still know the frequency being tuned to with a digital TV, but each frequency now carries a multiplex of several TV or radio channels.

https://en.wikipedia.org/wiki/Intermediate_frequency

[4rt]

Your RF knowledge is no-doubt sound, the people saying TV detector vans are impossible have no idea what they're talking about.

But, ultimately the tax isn't on TVs. The tax is applied to people watching broadcast live television and it's used to fund the BBC, ITV, Channel4 and also used to pay OFCOM which regulates all other media.

[defrost]

> Unless they peep through your windows?

If you search|scroll down the TV Licence article for "In 2013 it was revealed..." these days they can literally match flickering light seen through the window bouncing off the ceiling against currently broadcasting BBC | Channel 5, ITV, etc broadcasts.

See: Optical detectors

[exodust]

Interesting privacy issue. Personally I'd want to protect my own home's "light emissions" from peeping toms. My home, my light!

It's remarkable anyone thinks it's okay for a licensing authority to adopt this Orwellian creepiness. The slippery slope is technology increasingly reveals more detail from incidental light and audio coming from private households. We should act now in policy-making to protect this information as we do or should do for biometric data.

[NikkiA]

Freeview receives data on the same 4 core broadcasts* that were used for analog, and in fact, freeview channels remain mux'ed in a way that BBC produced content is isolated to the 2 muxes that correspond to the old BBC1/BBC2 split.

So yes, it's still perfectly easy to find the Intermediate Frequency oscillator for a freeview receiver.

* During the analog/digital crossover period, the DTV signals were, obviously, at an offset from the associated analog UHF channel, since analog and DTV could not physically occupy the same frequency, but the fact remains that the DTV muxes were associated with one of the 4 existing channels (Ch 5 didn't have an associated DTV mux afaik)

edit:

here's a list of the mux allocations, you'll notice that all BBC programming is allocated to the BBCA and BBCB muxes, even though there's more than 4 overall muxes available these days.

[NikkiA]

Hmm, for some reason HN stripped out the url on that edit

https://www.freeview.co.uk/corporate/platform-management/cha...