[cma-l] Singing posters and talking shirts stealing from your FM signal...

Fri Mar 10 17:18:41 GMT 2017

All you need is a really good experienced RF engineer - rather than a PhD student.
There are plenty around here (not me!) who will give you an authentic appraisal - probably for the fun of it.

Ian Hickling

Partner

[https://ci4.googleusercontent.com/proxy/2SkDsnIzSZgRbNnNKBSiwxiFhFQWRGV55mTjVL23fulnJpstZmYxeKrrYefY4qxiSgkMrAETld64XINLXCsujE_zI5gAsQyWeCWvHixcrNYtar3Sij4YlVBgN2NSQ-n2DsgZvrnpWZlfwCQ=s0-d-e1-ft#http://www.transplanuk.com/wp-content/uploads/2014/07/transplan_UK_weblogo_190x60.png]<http://www.transplanuk.com/>

Office: 016 3557 8435  (07h to 22h GTS)

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From: cma-l-bounces at mailman.commedia.org.uk <cma-l-bounces at mailman.commedia.org.uk> on behalf of Associated Broadcast Consultants <info at a-bc.co.uk>
Sent: 10 March 2017 14:22:25
To: The Community Media Association Discussion List
Subject: Re: [cma-l] Singing posters and talking shirts stealing from your FM signal...

Sounds like it is is a new version of "the rusty bolt"!

I just discovered today that my company has just employed a PhD student to look at this technology.  They are "uber-clever" chaps in our R&D department, so I think there might be something in it....

Glyn

On 10 March 2017 at 13:26, <tlr at gairloch.co.uk<mailto:tlr at gairloch.co.uk>> wrote:

Sort of, in that it is a product of intermodulation, but it's not 'spurious' in the sense that it is deliberate and controlled, chosen hopefully not to cause interference.

A plant is only a weed if it's not wanted!

Alex

On 10 March 2017 at 12:03 Ian Hickling <transplanfm at hotmail.com<mailto:transplanfm at hotmail.com>> wrote:

So - for "backscatter" read "spurious sideband"?

Ian Hickling

Partner

[http://www.transplanuk.com/wp-content/uploads/2014/07/transplan_UK_weblogo_190x60.png]<http://www.transplanuk.com/>

Office: 016 3557 8435  (07h to 22h GTS)

Car: 075 3098 0115 (only responds when driving)

6 Horn Street, Compton, NEWBURY, RG20 6QS

________________________________
From: cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk> <cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk>> on behalf of Alex Gray, Two Lochs Radio <tlr at gairloch.co.uk<mailto:tlr at gairloch.co.uk>>
Sent: 09 March 2017 13:30:55
To: 'The Community Media Association Discussion List'
Subject: Re: [cma-l] Singing posters and talking shirts stealing from your FM signal...

They don’t seem to be talking about inserting additional RDS data Ian, or indeed interfering with the RDS subcarrier in any way. If they only wanted data they point out they could use Bluetooth BLE, but this can’t carry audio. Their focus is on creating audio streams, and the option for data is simply to use the audio channels they are creating to carry FSK encoded data (ie a modem method). They needed massive error correction to achieve good data at a range of more than 2 metres, so the real throughput is reduced greatly.

One of the three schemes they describe is ‘overlay backscatter’ in which they “overlay arbitrary audio on ambient FM signals to create a composite audio signal that can be heard using any FM receiver”. They propose generating this in the first or second adjacent channel (eg a few hundred kHz away from the host signal) because broadcast planning means that is almost always guaranteed to be empty

Band II FM transmitters of 50nW or less don’t require a licence in the UK, so maybe they could get by with this for the audio version. However, they say they can achieve a range of up to 60 feet, which would usually need more like a microwatt of effective power.

For using potentially white space in the multiplex spectrum they have Stereo backscatter which applies to stations that are essentially mono audio but do broadcast a stereo multiplex (eg news/talk stations). They backscatter data and audio on these to achieve what they say is “a low interference communication link.” Note not ‘interference free’!

They also have a subsidiary technique to trick FM receivers receiving mono FM signals by inserting the stereo pilot signal and inserting their own audio interference free as the stereo subcarrier – effectively locally turning the mono station into a stereo one (that doesn’t seem a very novel or complex idea, and easily workable, but how many powerful FM stations operate in mono mode nowadays?).

Their third scheme requires two or more smartphones to cooperate to set up a sort of MIMO wireless scheme to null out the main FM transmission and give them cleaner reception of the intermodulated parasitic signal.

NB any unlicensed use of RDS for non programme-related data (“private data”) is prohibited at the moment. The coming of RDS2 might make it a lot harder for them to make used of ‘unused portions of the stereo signal” since RDS2 fills in a lot more of the ‘white space’ in the current multiplex spectrum.

But there’s still the question of legal provisions on unauthorized use of somebody else’s electricity (which have somewhat dubiously been used to prosecute hackers!), and of unauthorized interference with radio broadcasts.

Alex

From: cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk> [mailto:cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk>] On Behalf Of Ian Hickling
Sent: 09 March 2017 12:31
To: The Community Media Association Discussion List <cma-l at mailman.commedia.org.uk<mailto:cma-l at mailman.commedia.org.uk>>
Subject: Re: [cma-l] Singing posters and talking shirts stealing from your FM signal...

I think it's intimating that it can add on data in unused parts of the RDS section of a multiplex signal - eminently feasible - but I'd like to see how that propose achieving that.
And it would also requires licensing as a standalone transmitter.

Ian Hickling

Partner

[https://ci4.googleusercontent.com/proxy/2SkDsnIzSZgRbNnNKBSiwxiFhFQWRGV55mTjVL23fulnJpstZmYxeKrrYefY4qxiSgkMrAETld64XINLXCsujE_zI5gAsQyWeCWvHixcrNYtar3Sij4YlVBgN2NSQ-n2DsgZvrnpWZlfwCQ=s0-d-e1-ft#http://www.transplanuk.com/wp-content/uploads/2014/07/transplan_UK_weblogo_190x60.png]<http://www.transplanuk.com/>

Office: 016 3557 8435  (07h to 22h GTS)

Car: 075 3098 0115 (only responds when driving)

6 Horn Street, Compton, NEWBURY, RG20 6QS

________________________________

From: cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk> <cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk>> on behalf of Associated Broadcast Consultants <info at a-bc.co.uk<mailto:info at a-bc.co.uk>>
Sent: 09 March 2017 11:56:23
To: The Community Media Association Discussion List
Subject: Re: [cma-l] Singing posters and talking shirts stealing from your FM signal...

Alternatively you could say the original transmission IS indeed unchanged.  It is the identical signal broadcast from a big mast miles away and there is no way this system can change that.

What it's changing is the reflection environment from what I understand.  Maybe a bit analagous to sonar or radar.

But maybe I understand wrongly!

Glyn

On 9 March 2017 at 11:42, Alex Gray, Two Lochs Radio <tlr at gairloch.co.uk<mailto:tlr at gairloch.co.uk>> wrote:

Exactly Ian -    I guess he means “…without significantly affecting the original transmissions…” or perhaps he’s found some new laws of physics.

Interesting technique though if you read the full details. Reminds me of the cunning Russian passively bugged ‘friendship’ emblem that sat in the US Embassy in Moscow for some time. Also the (apocryphal I think) tale of the farmer prosecuted for lighting his house using power tapped off the near field of the Droitwich log wave transmitter.

Alex

From: cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk> [mailto:cma-l-bounces at mailman.commedia.org.uk<mailto:cma-l-bounces at mailman.commedia.org.uk>] On Behalf Of Ian Hickling
Sent: 08 March 2017 22:37
To: The Community Media Association Discussion List <cma-l at mailman.commedia.org.uk<mailto:cma-l at mailman.commedia.org.uk>>
Subject: Re: [cma-l] Singing posters and talking shirts stealing from your FM signal...

".......we developed a new way of communication where we send information by reflecting ambient FM radio signals that are already in the air, which consumes close to zero power.” The UW team has — for the first time — demonstrated how to apply a technique called “backscattering” to outdoor FM radio signals. The new system transmits messages by reflecting and encoding audio and data in these signals that are ubiquitous in urban environments, without affecting the original radio transmissions......"
Oh yeah?

Ian Hickling

Partner

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